Phytoseiid mites (Acari: Gamasina) in Finnish apple plantations with reference to integrated control of phytophagous mites Tuomo Tuovinen Agricultural Research Centre of Finland Institute of Plant Protection FIN-31600 Jokioinen, Finland Academic dissertation To be presented, with the permission of the Faculty of Agriculture and Forestry of the University of Helsinki, forpublic criticism in AuditoriumXII on May 26th, 1993, at 12 o'clocknoon. https://www.c-info.fi/en/info/?token=vTRT4tjJz1hxcd73.YSql7km85NPmhQvY-rL-SA.Cz4sGylkFmCktARlCkh861VnmJVjSZOVET2XvSTWOnDZdPiZTzKQ3Rd2oKN7Y4H13Dn800VqxaoEbUV89LchWuFw9HDFCnvl7otW22cR6i978rnOy63v2V2M8SjeTQHIRPd2yoSd8YM1aemyeBtMM_cMzrpxFElWv-oQekmyhCfUFFcNKSllAvAox-3kB0RSishlCPVKeBw1DUNgyULF3Ey46uh9x8fm4LVapYCCFDMqcuBp_rI7e_Gu5uKzjpTZppKkAN4 2 3 PREFACE This study was carried out at the Agricultural Research Centre ofFinland, Institute ofPlant Protection in Jokioinen, during 1981-1992.1am most grateful to Professor Martti Markkula for his encouragement in the beginning ofmy research work and forprecious criticism and comments on part of the manuscripts of the original articles. I also want to express my thanks to Professor Unto Tulisalo, my teacherin agricultural entomology, for his support in my first steps in entomological research. 1 am deeply grateful to Professor Anna-Liisa Varis for her valuable comments and guidance during this work and for her constructive criticism on the manuscript of this thesis. My sincere thanks are dueto all my colleagues at the Institute of Plant Protection. I want to thank Dr. Sirpa Kurppa, Professor Heikki Hokkanen, Dr. Kari Tiilikkala and Mr. Seppo Korpela, for their critical and helpful comments on manuscripts of the original articles. Their and my other colleagues’ support was important also in my decision to start the postgraduate studies and to work on this thesis. Special thanks are due to Professor Danuta Kropczynska, University ofWarsaw, whose visit at the Agricultural Research Centre in 1985 actually was the beginning of the work that led into this thesis. Her helpful advice and warm encouragement during this research has been ofgreat value to me. I express my sincere gratitude to my co-author ofan original article, Mr. Joost Rokx, for taking part in my studies in 1989. The assistant technicians, especially Ms. Tarja Kallio, Ms. Satu Smolander and Ms. Arja Hämäläinen, have done valuable work in sampling, counting and preparing mites. I want to express my warm gratitude to them. Last but certainly not least, I want to thank my wife Tiina and my family whose support and encouragement have helped me complete this work. Tammela, March 1993 Tuomo Tuovinen 4 LIST OF ORIGINAL ARTICLES The original articles summarized here are: I Tuovinen, T. 1993. Identificationkeys and notes on the occurrence ofphytoseiid mites (Gamasina: Phytoseiidae) in Finnish apple plantations and their surroundings. Ento- mologica Fennica (in press). II Tuovinen, T. & Rokx, J.A.H. 1991. Phytoseiid mites (Acari: Phytoseiidae) on apple trees and in surrounding vegetation in southern Finland. Densities and species com- position. Experimental & Applied Acarology 12: 35-46. 11l Tuovinen, T. 1993. Influence of surrounding trees and bushes on the phytoseiid mite fauna on apple orchard trees in Finland. Agriculture, Ecosystems & Environment (in press) IV Tuovinen, T. 1989. Chemical control of European red spider mite Panonychus ulmi (Koch). I. Evaluation of flubenzimine. Annales Agriculturae Fenniae 28: 317-332. V Tuovinen, T. 1990. Chemical control of European red spider mite Panonychus ulmi (Koch). 11. Evaluation of clofentezine and hexythiazox. Annales Agriculturae Fenniae 29: 195-204. VI Tuovinen, T. 1990. Effect of four fungicides on phytophagous and predatory mites on apple trees. Annales Agriculturae Fenniae 29: 205-215. In the following text, these articles are referred to by the above Roman numerals. 5 CONTENTS PREFACE 3 LIST OF ORIGINAL ARTICLES 4 ABSTRACT 7 INTRODUCTION 8 1 Importance ofphytoseiid mites on apple 8 2 Pest status of phytophagous mites on apple 8 3 Apple pest management 9 3.1 Use of pesticides 9 3.2 Control of mites 9 3.3 Current and future concepts of pest management 9 4 Objectives of the study 10 MATERIALS AND METHODS 10 1 Survey of phytoseiid species 10 2 Effect of surrounding vegetation 11 3 Experiments with pesticides 11 3.1 Acaricide and insecticide experiments 11 3.1.1 Laboratory experiments 11 3.1.2 Field experiments 11 3.2 Fungicide experiment 12 RESULTS AND DISCUSSION 13 1 Occurrence and role of mites on apple 13 1.1 Mite populations on sprayed and unsprayed trees 13 1.2 Phytoseiid species and their relevance in integrated control 15 1.3 The role ofphytoseiid mites on apple trees 19 2 Surrounding vegetation as a source of phytoseiid mites 21 3 Pesticides in mite management 23 3.1 Acaricides 23 3.1.1 Flubenzimine 23 3.1.2 Clofentezine 24 3.1.3 Hexythiazox 24 3.2 Insecticides 25 3.3 Fungicides 25 3.3.1 Bitertanol 25 3.3.2 Dichlofluanid 25 3.3.3 Dithianon 26 3.3.4 Triforine 26 SUMMARY AND CONCLUSIONS 26 REFERENCES 27 SELOSTUS 32 6 Phytoseiid mites (Acari: Gamasina) in Finnish apple plantations with reference to integrated control of phytophagous mites Tuomo Tuovinen Tuovinen, T. 1993. Phytoseiid mites (Acari: Gamasina) in Finnish apple planta- tions with reference to integrated control of phytophagous mites. Agric. Sci. Finl. 2: Supplement No. 1. 33 p. (Agric. Res. Centre of Finland. Inst. PI. Protect., FIN-31600 Jokioinen, Finland.) On apple tree leaves, the most abundant predatory phytoseiid species were Euseius finlandicus (Oudemans), comprising 39% of specimens found in surveys in 1985 and 1989, Phyloseius macropilis (Banks), 32%, and Paraseiulus soleiger (Ribaga), 18%. Amblyseius subsotidus (Beglyarov) and A. reductus Wainstein occurred occasionally in relatively high densities, whereas Anlhoseius rhenanus (Oudemans), A. suecicus (Sell- nick), A. richteri (Karg), A. bakeri (Carman), A. viktorovi Wainstein, Paraseiulus taihii (Athias-Henriot) and P. triporus (Chant & Yoshida-Shaul) occurred rarely and always in low densities. On unsprayed trees, the mean density of phytoseiid mites was 1.2 mites/leaf. On sprayed trees, none or only a few phytoseiids were found, but the density of the European red spider mite Panonychus ulmi (Koch) was much higher than on unsprayed trees.Indigenous phytoseiid mites appeared to be capable of maintaining the P. ulmi population level under the economic threshold on unsprayed apple trees. The presence of the common prey mites, P. ulmi, the rust mite Aculus schlechtendali (Nalepa), or tydeid mites was not necessary for the presence of phytoseiid mites. Relatively high numbers of E. finlandicus, P. macropilis and P. soleiger were found, although prey mites were scarce. Many deciduous trees and bushes support high populations of phytoseiid mites. The highest numbers were found on Aesculus hippocastani, Corylus avellana, Fraxinus excelsior, Ribes nigrum. Rubus odoralus, Sorhus aucuparia, Tiliä spp. and Ulmus glabra. E. finlandicus occurred most commonly and in the highest densities, followed by P. macropilis, P. soleiger, P. triporus and A. rhenanus. E. finlandicus can immigrate rapidly from adjacent vegetation into an orchard after harmful spraying if suitable plants are present, and tall trees appeared to be more important than low bushes as natural sources of phytoseiids for aerial dispersal. In acaricide tests, flubenzimine was effective against P. ulmi, but it was harmful to E. finlandicus and P. macropilis. A single treatment with clofentezine and hexythiazox, although effective against P. ulmi, was harmless to E. finlandicus and P. macropilis, but repeated sprays of both acaricides significantly reduced the density of phytoseiids. The fungicides dithianon and bitertanol were harmless to phytoseiids, but di- chlofluanid was harmful. Triforine sprays also reduced the numbers ofphytoseiid mites, but the effect was only temporary. It had a 75% effect on P. ulmi winter eggs when sprayed just before hatching. Dichlofluanid was effective against P. ulmi and A. schlechtendali. Key words: Phytoseiidae, Panonychus ulmi, Aculus schlechtendali. apple, integrated control, natural control, chemical control, side effects ofpesticides 7 Agric. Sei. Fint. Suppl. No. 1 (1993) INTRODUCTION Over 1600 species are known in the family Phyto- seiidae (Acari: Gamasina) (Chant and Yoshida- Shaul 1991). Phytoseiid mites are predators of spider mites (Tetranychidae), eriophyid gall mites (Eriophyidae), tarsonemid mites (Tarsonemidae) and tydeid mites (Tydeidae). A few species are also reported to consume insects, e.g. thrips (Overmeer 1985). 1 Importance of phytoseiid mites on apple Numerous studies have demonstrated that phyto- seiid mites can effectively regulate spider mite populations on fruit trees (Dosse 1960, Collyer 1964, Wildbolz and Staub 1986). Rabbinge (1976) showed in a comprehensive simulation study on the effect ofa phytoseiid mite Amblyseius andersoni (Chant) [A. potentillae (Garman)] on the European red spider mite Panonychus ulmi (Koch) in an apple tree environment that a wide range of prey-predator ratios is functional. The direct use of phytoseiids to control spider mites in orchards is also well documented (Croft and Barnes 1971, McMurtry and van de Vrie 1973, Hoy 1982, loriatti et al. 1983, Seier 1989, Trapman 1989). In many cases, the introduced phytoseiid mites have been conserved by using selective pesticides, to which they are resistant (Overmeer and van Zon 1983, Solomon and Easterbrook 1983, Solomon and Fitzgerald 1984, Genini and Baillod 1987, Minks et al. 1988, Solomon 1988). In Europe, Typhlodromus pyri Scheuten and A. andersoni are the two most commonly used phyto- seiid species in integrated pest management (IPM) programmes. These species occur commonly and have strains resistant to organophosphorous insect- icides (OPs) (Hoyt 1972, Cranham et al. 1983, Overmeer and van Zon 1983,Hadam et al. 1986, Genini and Baillod 1987). T. pyri is able to main- tain spider mite populations under economic thresholds in commercial orchards (WILDBOLZ and Staub 1986, Genini and Baillod 1987). Some other phytoseiid species have also been considered to be important in European conditions, e.g. Euseius finlandicus (Oudemans) (Sechser et al. 1984). Considerable numbers of phytoseiid species have been identified in recent surveys on apple and many other plants in Denmark and Norway (Ed- land 1986, Hansen and Johnsen 1986,Edland 1987,Karg and Edland 1987). In Sweden, SELL- NICK (1958) reported ofeight species on cereals and grasses. In Finland, phytoseiid mites have not pre- viously been surveyed, but reports concerning a part of the present data have been published (Kropczynska and Tuovinen 1987,1988). Listo et al. (1939) mentioned predatory mites as natural enemies of P. ulmi, but data on the species in ques- tion were not presented. Kanervo (1961) listed important natural enemies of P. ulmi found to occur on apple in Finland, and included 'Typhlodromus sp.’ as one of the high priority species. Listo et al. (1939) even presented the results offeeding studies on an unidentified phytoseiid species and con- cluded that the species was an efficient predator of P. ulmi. 2 Pest status of phytophagous mites on apple In northern Europe, P. ulmi is the most important tetranychid species on apple (van de Vrie 1985). It is most common in orchards where intensive cul- tivation methods have been applied (Listo et al. 1939, Post 1962, Cranham 1979).One reason for the higher densities in well-kept orchards than in home gardens is the better nutritional conditions for spider mites: owing to pruning and fertilization, the quality of leaves as a food source for P. ulmi is better than in abandoned trees (Post 1962). How- ever, it is the harmful effect of wide-spectrum in- secticides on the natural enemies of P. ulmi that is considered to be the most important reason for the injuriousness of P. ulmi (McMurtry et al. 1970, van de Vrie 1972,Croft and Brown 1975). Nu- merous cases of resistance to pesticides in P. ulmi show that mite problems are not easy to control by 8 Agric. Sd. Finl. Suppt. No. 1 (1993) chemical means alone (Helle and van de Vrie 1974, Cranham 1982, Cranham and Helle 1985, Free and Wagner 1987, Dennehy et al. 1988). P. ulmi is the only serious mite pest in commer- cial apple orchards in Finland (Ltsxo et al. 1939, Kanervo 1960,Vappula 1965),and its pest status has persisted despite the introduction of specific acaricides (Tuovinen 1992a). The other common spider mite species in this country, the two-spotted spider mite Tetranychus urticae (Koch), occurs only occasionally on apple trees. An eriophyid mite, the apple rust mite Aculus schlechtendali (Nalepa), is not rated as a serious pest on apple in Finland, although it is capable of damaging apple trees (Vappula 1965). In Sweden, though, this mite has lately caused considerable damage (Tor- neus 1990), and recent observations have shown that it has become more common in Finland, too (Tuovinen, unpubl.). Other eriophyid mites found on apple, Phyllocoptes malinus (Nalepa), which occurs on old, neglected trees, and Phyllocoptes mali (Nalepa), which is very rare, are not rated as pests (Vappula 1965). Listo et al. (1939) and Kanervo (1961, 1967) studied the natural enemies of P. ulmi in Finland, focusing on insect predators and their conservation. After their studies, the biological control of P. ulmi was largely ignored in practice, and growers were advised to use acaricides to combat the increasing mite populations. The problems that arose in the 1960 s were partly due to the resistance of P. ulmi to OP insecticides. When used in the 19505, they had been effective against P. ulmi (Heikinheimo 1956), but later less so (Markkula and Kurppa 1985). The destructive effect of OPs on natural insect enemies of P. ulmi was documented quite soon (Kanervo 1961). 3 Apple pest management 3.1 Use of pesticides In 1984-1989, the average number of sprays in commercial apple orchards included 2.1-3.7 insect- icide, 1.1-1.7 acaricide and 5.3-7.3 fungicide sprays (Tuovinen 1992a). Most of the insecticides were OPs although some pyrethroids were also used. The main acaricide was chinomethionate plus several minor products, and the main fungicides were dithianon and bitertanol plus a few minor products. The common target insects in Finnish apple orchards are the apple fruit moth Argyresthia conjugella Zell., tortricids e.g. Hedya nubiferana (Hw.), the codling moth Cydia pomonella (L.), the winter moth Operophtera hrumata L., the aphids Aphis pomi L. and Dysaphis spp., and several heteropterous bug species (Lygus spp., Plesiocoris rugicollis Fall.). Acaricides were used almost ex- clusively to control P. ulmi, and fungicides to con- trol the apple scab Venturia inaequalis (Cooke) Winter. 3.2 Control of mites In Finland, P. ulmi has been controlled by chinome- thionate and dicofol, which are usually applied at the timeof flowering in May-June, orby oxydeme- tonmethyl. Only a few growers apply mineral oil sprays against winter eggs in spring. Registration of dicofol is no longer valid (BLOMQVIST et al. 1992). In warm and dry seasons, when P. ulmi densities tend to grow too high, extra sprays have been ap- plied later in the season. Despite the average or higher number of sprays, P. ulmi numbers are still too high in some orchards (Tuovinen 1992a). Res- istance to chinomethionate and dicofol has been reported in P. ulmipopulations in Europe and North America (Cranham and Helle 1985, Riedl et al. 1992). Resistance to acaricides in Finnish P. ulmi strains has not been studied in the laboratory, but control failures indicate that resistance occurs in some orchards (Tuovinen, unpubl.). A. schlechtendali has not been a serious pest in Finland, but lately some damage caused by it has been recorded. It has been controlled mainly by chinomethionate or insecticides sprayed against other pests. 3.3 Current and future concepts of pest management Integrated pest management, IPM, has been a lead- 9 Agric. Sei. Finl. Suppl. No. 1 (1993) ing concept for pest control research in many coun- tries since the 1950 s (Wearing 1982). In Finland, Listo et al. (1939) already oriented towards IPM. The first successes with IPM in fruit orchards were obtained in Canada (PICKETT et al. 1958), since then IPM methods have been successfully applied and become accepted practice in the USA (Croft 1975), Europe (GRUYS 1975,WILDBOLZ 1979) and New Zealand (Wearing et al. 1978). One of the benefits of IPM methods is that mite pests are gen- erally controlled by introduced or naturally occur- ring, conserved predators. The availability of these predators is assured by using selective pesticides which do not harm natural enemies, e.g. phytoseiid mites (Wearing et al. 1978). Later, the term ’lntegrated Fruit Production’ (IFP) was introduced to expand the principles of IPM to cover the whole growing system, including all growing techniques that may affect plants, pests and natural enemies. In the joint statement of the lOBC (International Organization for Biological and Integrated Control of Noxious Animals and Plants) working group ’lntegrated plant protection in orchards’ and the ISHS (International Society for Horticultural Science) working group ’lntegrated fruit production’, in ’General principles, guidelines and standards for integrated production of pome fmits in Europe, and procedures for endorsement of national or regional guidelines and standards’, they state under the heading ’lntegrated plant protec- tion’ that, "Populations ofkey natural enemies (eg., Phytoseiid mites on apple or Anthocorid predators on pear) must be preserved. This means plant pro- tection products toxic to them may not be used. Where Phytoseiid predators are absent from apple orchards, they should be introduced where neces- sary." (Dickler and Schäfermeyer 1991). However, before the above principles can be followed, it is necessary to know the local status of phytoseiid populations. 4 Objectives of the study The study covers six main areas: 1) keys to and descriptions of the phytoseiid mites found in Finland (I); 2) the occurrence and species composition of phy- toseiid mites on sprayed and unsprayed apple trees (I, 11, III); 3) the occurrence ofphytoseiid mites on deciduous trees and bushes (II); 4) the effect of surrounding vegetation on the oc- currence of phytoseiid mites in apple orchards (in); 5) the effect of acaricides on phytophagous and predatory mites (IV, V); and 6) the side effects offungicides on the mites inhab- iting apple leaves (VI). The main purpose of the study is to provide basic information on naturally occurring species of Phy- toseiidae. As the taxonomy of the family Phyto- seiidae is not well known, keys to and short descrip- tions of the species occurring in Finland are also given. The value and characteristics of phytoseiid mites as natural enemies of P. ulmi and A. schlechtendali in Finnish apple orchards are evalu- ated in the light of results and a literature search from other countries. Information is also given about the application of mite management methods as well as effective use of acaricides. MATERIALS AND METHODS 1 Survey of phytoseiid species Apple leaf samples (N=l46) were collected in southern Finland from sprayed apple trees in com- mercial orchards and from unsprayed trees in home gardens, mainly in August and September, in 1985 and 1989 (I). In 1989, samples (N=s4) from other deciduous trees and bushes around orchards were also inspected (II). Phytoseiid mites were prepared and identified, and other mites were either counted or estimated (1985) or only eriophyid and tetrany- chid mites were estimated (1989). During the study period, some 4400 phytoseiid mite specimens on apple trees, and 5000 specimens 10 Agric. Sd. Finl. Suppl. No. 1 (1993) on other plants were prepared and identified. These specimens served as reference materials for the keys to and notes on host plants of the species of the family Phytoseiidae in Finland. The generic classi- fication used herein follows mainly that of Karg (1983) (I). 2 Effect of surrounding vegetation The study comprised 14 normally sprayed commer- cial apple orchards in 1989 (selected orchards sur- veyed in II) and one sprayed orchard surveyed in 1991 (III). Leaf samples were collected from sprayed and unsprayed apple trees if available nearby, and from the main species of deciduous trees and bushes in the vicinity. The phytoseiid species composition on sprayed and unsprayed apple and on the main vegetation in the vicinity was analysed and compared in each orchard. In 1991, the vegetation around and within a 2-ha orchard was surveyed, and the compositions of phytoseiid species and their numbers were compared with those in the nearest surrounding vegetation. 3 Experiments with pesticides 3.1 Acaricide and insecticide experiments The effect of clofentezine (Apollo, Schering), flubenzimine (Cropotex, Bayer) and hexythiazox (Nissorun, Nippon Soda) on P. ulmi and other mites inhabiting apple trees was studied in field and laboratory experiments (IV, V). Observations of the effect of the following other acaricides and insect- icides are included: chinomethionate (Morestan, Bayer), deltamethrin(Decis 25 EC, Hoechst), dico- fol (Kelthane, Rohm and Haas), diflubenzuron (Dimilin, Duphar 8.V.), fenbutatinoxide (Torque, Shell), mineral oil (Ovipron, BP) and oxydemeton- methyl (Metasystox, Bayer). The pesticides tested in the field experiments are summarized in Table 1. 3.1.1 Laboratory experiments The effect of ovicidal acaricides on P. ulmi winter eggs was evaluated in the laboratory with the help of a Potter tower. Tests with clofentezine and hexythiazox were carried out using eggs at different stages of development (V). The evaluation tech- nique was largely as follows: 1) winter eggs from one orchard were used per test; 2) small, halved pieces of twig, each containing 20-50 eggs, were placed on Petri dishes and sprayed with 2 ml liquid per spray; 3) at least four replicates, with at least 100eggs/rep- licate, were sprayed; 4) control dishes were sprayed with pure water; 5) the pieces of twig were circled with insect glue to catch all hatched larvae; 6) Petri dishes containing the pieces of twig were preserved in a growing chamber at +2O/+l5 °C, 75±10% Rh and 13/11 h L/D photoperiod; 7) 2 and 4 weeks later the hatched larvae inside the circle of glue were counted. 3.1.2 Field experiments Field experiments were carried out in 1981-1989 in experimental orchards using a randomized block design with 3-4 replicates of single or 2-6 trees, or in commercial orchards in 0.5-1 ha blocks (IV, V). In the experimental orchards, sprays were applied with a handgun sprayer, and in commercial orch- ards with a tractor mistsprayer; 300-400 1/ha water was used. The effect of acaricide treatments was assessed several times during the summer and, in most cases, winter eggs were inspected later in the autumn. Usually, the number of mites was also counted before the sprays. Some of the experiments were designed to enable the effect of spraying to be monitored during the following season (IV). To assess the effect of sprays, leaves were inspected under a stereomicroscope, and mobile stages and eggs of P. ulmi were counted. The other mite groups, phytoseiid mites and tydeid mites (Acari: Tydeidae) were counted when appropriate, and numbers oferiophyid mites were estimated. In two experiments, the occurrence ofpredators other than phytoseiids was evaluated from beating samples (V). 11 Agric. Sei. Fint. Suppl. No. 1 (1993) Table I. Summary of the pesticides tested in field experiments (IV,V,VI) Active ingredient Product A.i. g/100 1 References Bitertanol Baykor 50 VI Figs. 2-6; Table 2 Chinomethionate Morestan 37.5 IV Figs. 3a,b 55 IV Table 7 62.5 IV Figs. 3a,b V Tables 3,5,6 Clofentezine Apollo 25 V Table 7 50 V Table 9 85 V Table 7 100 V Tables 3,4 Deltamethrin Decis 25EC 2.5 IV Table 4 6.25 IV Table 5 Dichlofluanid Euparen 400 VI Figs. 2-6; Table 2 Dicofol KelthaneW 139 IV Table 5 Diflubenzuron Dimilin 125 IV Tables 3,5 Dithianon Delan 180 VI Figs. 2-6; Table 2 Fenbutatinoxide Torque 250 IV Tables 4,5 Flubenzimine Cropotex 25 IV Table 8 85 IV Table 8 150 IV Figs. 3a,b; Tables 3,7 200 IV Figs. 3a,b 250 IV Figs. 3a,b; Tables 4,5,6 V Table 4 Flucythrinate Cybolt 10 IV Table 5 Hexythiazox Nissorun 5 V Table 7 10 V Table 9 12.5 V Table 5 15 V Tables 6,8 17 V Table 7 Mineral oil Ovipron 2910 V Table 9 Oxydemeton-methyl Metasystox R 132.5 IV Figs. 3a,b Triforine Saprol 96 VI Figs. 2-6; Table 2 3.2 Fungicide experiment The following fungicides are permitted for use against apple scab in Finland: bitertanol (Baykor, Bayer), copperoxychlorid (Kuprijauhe, Hoechst, and OB 21, Bayer), dichlofluanid (Euparen, Bayer), dithianon(Delan, Shell Agrar) and triforine (Saprol, Shell Agrar). Copperoxychlorid is not re- commended for commercial orchards, and so was not tested (Table 1) (VI). The effect of fungicide sprays on P. ulmi winter eggs bef ore they hatched was studied in the labor- atory with a method similar to that used forovicidal acaricides (see 3.1.1). The effect of direct sprays on young P. ulmi larvae was studied using a Potter tower. Single leaves with 25 larvae each were sprayed. The test units were then kept in a growing chamber, and the development of larvae to nymphal and adult stages was monitored for 11-16days. 12 Agric. Sei. Finl. Suppl. No. 1 (1993) A field experiment was conducted in an aban- donedorchard in 1989 to test the effect of fungicide sprays on P. ulmi and other mite species occurring in the orchard. The trees were sprayed four times in June-July. Samples of 50 leaves were collected twice after the sprays and later in September. Eggs and mobile stages of P. ulmi, mobile stages of phytoseiid and tydeid mites were counted, and the numbers of eriophyids were estimated. The com- position of phytoseiid species was investigated. RESULTS AND DISCUSSION 1 Occurrence and role of mites on apple 1.1 Mite populations on sprayed and unsprayed trees The survey conducted in 1985, reported by Kropczynska and Tuovinen (1988), and the sur- vey made in 1989 (II) show that phytoseiid mites occur more abundantly and frequently on un- sprayed than on sprayed trees (Figures. 1 and 2). For the statistical analysis, 19 inappropriate samples were excluded from the original data of Kropczynska and Tuovinen (1988) in order to make the material geographically more compatible between years. The number (mean±SE) of phyto- seiid mites/leaf on unsprayed trees, 1.62+0.26 and 1.15±0.19, was significantly greater than on sprayed trees, 0.03410.023 and 0.054+0.022, in 1985 and 1989, respectively (Kruskal-Wallis One- way ANOVA, Chi2=55.35, Ngs=79, PcO.001; Chi 2=27.65, Nx9=4B, P<0.001). The sprayed samples were from commercial, well-kept orch- ards, and as a rule sprayings included several fungi- cide (4-11), acaricide (0-3) and insecticide (0-4) treatments (II). Most of the unsprayed samples were from abandoned trees in home gardens. In 1989,phytoseiid mites were found in over 60% of sprayed orchards but in 1985 in only 24% (Fig. 2). The difference is thought to result from the differ- ence in inspection procedures, as the washing method used in 1989 allows very low numbers of mites to be detected more readily than the visual inspection practised in 1985. The presence of phytoseiid mites in abandoned or unsprayed apple trees and their low density on sprayed trees were consistent with the findings of earlier studies conducted in more favourable apple growingareas (Collyer 1964,Knisley and Swift 1972, Amano and Chant 1990, Thistlewood Fig. I. Abundance of mites inapple leaf samples in 1985 and 1989. (Kropczynska and Tuovinen 1988,1, II). Sprayed apple Fig. 2. Occurrence of mites in apple leaf samples in 1985 and 1989. (Kropczynska and Tuovinen 1988,1, II). 13 Agric. Sei. Finl. Suppl. No. 1 (1993) 1991). Many species of phytoseiid mites are also common on unsprayed apple trees in Norway, a country geographically and climatically close to Finland (Edland 1987). The occurrence and number of phytoseiid mites on sprayed trees were low even though relatively few harmful sprays were used (Fig. 1, II). Phyto- seiid mites have been found in higher densities in the USA, Canada and Europe, despite more numer- ous sprayings (Lienk et al. 1980, Croft et al. 1990). This can be explained by the resistance to pesticides of T. pyri and Metaseiulus occidentalis (Nesbitt), the two predominant species in sprayed orchards in North America (Croft and Strickler 1983). In Canada, Thistlewood (1991) found a mean of 0.15 phytoseiids/leaf in 38 commercial orchards treated with a mean number of 4.5 insect- icide and 2 acaricide sprays. In these orchards, the main species was Amhlyseius fallacis Carman, which has not been recorded in the Nordic coun- tries. This species is resistant to many commonly applied pesticides (Croft and Meyer 1973, Strickler and Croft 1982). Recently, up to 5- fold resistance to azinphosmethyl and dimethoate has been noticed inFinnish colonies ofE. finlandi- cus, collected from OP-treated trees, compared to colonies that never have been sprayed with insect- icides (Tuomas Kostiainen, pers. comm.). Even though the observed resistance is not high com- pared to that found in A. fallacis, M. occidentalis or T. pyri , it might improve integrated mite control especially if lower concentrations of OPs can be applied. E. finlandicus and P. macropilis were the most abundant phytoseiid species on both unsprayed and sprayed apple trees,and accounted for almost three- quarters of all phytoseiid specimens (Figs. 3 and 4). The remaining quarter of the specimens included 10 species, of which Paraseiulus soleiger (Ribaga) was the most abundant one in 1985,but Amhlyseius subsolidus Beglyarov in 1989. In 1985, the species found on sprayed trees consisted almost entirely of P. macropilis and E. finlandicus, whereas in 1989, P. soleiger was also present. The higher abundance of P. macropilis on sprayed trees in 1985 was de- duced from a single sample containing 95% of the individuals of the species. E. finlandicus was found in 18% and 40% of sprayed samples, but P. macropilis was present only in 10% and 17% in 1985and 1989,respectively. Spider mite numbers, almost entirely P. ulmi, Fig. 3. Composition and relative abundance of phytoseiid mites in apple leaf samples in 1985. Relative numbers are based on identified subsamples if more than 100 mites were found. (Kropczynska and Tuovinen 1988,1). Fig. 4. Composition and relative abundance of phytoseiid mites in apple leaf samples in 1989. (II) 14 Agric. Sei. Finl. Suppl. No. 1 (1993) were significantly higher on sprayed trees than on unsprayed trees in 1985 (Fig. 1) (Mann-Whitney U-test, z=-4.58, N=79, Pll mites per leaf). The situation was exactly the same in 1989, when the number of P. ulmi was estimated in only part of the orchards (Mann-Whit- ney U-test, z=4.38, N=26, PcO.OOI, calculated from scored values). There were big differences between commercial orchards in the density of P. ulmi, even in orchards with similar spraying pro- grammes. Spider mites caused continuous prob- lems in some orchards, but in others, mite density was rather low. On untreated trees, though, spider mite density was consistently low, under 5 mites/leaf. The mean of 15 mobile stages of mites/leaf in 1985 is considerably higher than the threshold for control of P. ulmi in the Netherlands, varying from 2/leaf to 7/leaf, depending on the time of season (Rabbinge 1985). There is no single economic injury level for apple, but many variable levels depending on growing conditionsand weather, cul- tivars, and the presence of predatory mites (van de Vrie 1985, Freier et al. 1992, Hardman 1992). The maximum numbers of P. ulmi recorded in this study were as high as 105 and 95 mobile mites/leaf (IV, V). There is no doubt that P. ulmi causes severe injuries and yield losses in part of the commercial orchards. The question of the economic injury level and the assessment of the spraying threshold are beyond the context of this study. The numbers of the eriophyid mite A. schlechten- dali were significantly higher on sprayed than on unsprayed trees in 1989 (MannWhitney U-test, z=-2.27, N=4B, P=0.024, calculated from scored values), but not in 1985 (Fig. 1). Tydeid mites were observed only in 1985,and they were more numer- ous on unsprayed trees than on sprayed trees (MannWhitney U-test, z=-5.77, N=79, P<0.001) (Fig. 1). Tarsonemid mites were quite scarce, and they occurred equally on sprayed and unsprayed trees (Fig. 1). Spider mites, eriophyids, tydeids and tarsone- mids can serve as prey for many phytoseiid species. Of the pest mites, eriophyids such as A. schlechten- dali can be considered advantageous for the bio logical control of P. ulmi if their density is not so high that it causes bronzing ofleaves or russeting of apples (Easterbrook and Fuller 1986, Solhoy et al. 1991). On unsprayed trees, tydeid mites were even more common than spider mites. As tydeid mites feed on honeydew and Cladosporium fungi, pollen and various plant debris (Gerson 1985), they are not harmful to apple trees and are therefore considered a useful supplementary source of food for phytoseiid mites. In the Netherlands, tydeids were a more suitable food for T. pyh than for A. andersoni, but there may be differences between strains in the utilization of food sources (Calis et al. 1988). The presence of alternative food sources, including pollen and other food of plant origin, for predatory mites is an important reason for continu- ing control ofP. ulmi. Karg (1992) suggested that a common tydeid species, Tydeus caudatus (Ant. Duges), should be included in tests of the side effects of pesticides. As a representative of ’indif- ferent species’, it may enhance control ofP. ulmiby phytoseiid mites. In some of the acaricide tests and in the fungicide test tydeid mites were taken into account in this study (V, VI). 1.2 Phytoseiid species and their relevance in integrated control The phytoseiid species found in this study are listed in Table 2. Three species imported to Finland and released in glasshouses are included (1). In the following, the species considered import- ant or interesting for the integrated control of phy- tophagous mites on apple trees in Finland are shortly characterized and discussed. There are many other species, which have only little value for the integrated control on apple trees, because they do not occuron apple trees orare very rare (I). Most of the articles on the use of phytoseiid mites in biological control concern Phytoseiulus persimilis Athias-Henriot, a species used in glasshouses for the control of T. urticae, or T. pyri, M. occidentalis, A.fallacis and A. andersoni, which are used for the control of P. ulmi in fruit orchards in USA, New Zealand and Europe. 15 Agric. Sei. Fint. Suppl. No. 1 (1993) Table 2. Phytoseiid species recorded in Finland (I). PHYTOSEIIDAE Berlese, 1916 PHYTOSEIINAE Berlese, 1916 Phytoseius Ribaga,l9o2 Phytoseius juvenis Wainstein & Arutunjan, 1970 Phytoseius macropilis (Banks, 1909) Sei uius Berlese, 1887 Seiulus aceri (Collyer, 1957) Paraseiulus Muma, 1961 Paraseiulus soleiger (Ribaga, 1902) Paraseiulus talhii (Athias-Henriot, 1960) Paraseiulus triporus (Chant & Yoshida-Shaul, 1982) Anthoseius De Leon, 1959 Anthoseius hakeri (Gartnan, 1948) Anthoseius rhenanus (Oudemans, 1905) Anthoseius richteri (Karg, 1970) Anthoseius sueeieus (Sellnick, 1958) Anthoseius viktorovi Wainstein, 1975 Typhlodromus Scheuten, 1857 Typhlodromus andrei Karg, 1982 Typhlodromus laurae Arutunjan, 1974 Typhlodromus pyri Scheuten, 1857 AMBLYSEIINAE Berlese, 1916 PhytoseiulusEvans, 1952 Phytoseiulus persimihs Athias-Henriot, 1957 Proprioseiopsis Muma, 1961 Proprioseiopsis okanagensis (Chant, 1957) Euseius Wainstein 1962 Euseius finlandicus (Oudemans, 1915) Amhlyseius Berlese 1914 Amhlyseius barkeri (Hughes, 1948) Amhlyseius cucumeris (Oudemans, 1930) Amhlyseius reductus Wainstein, 1962 Amhlyseius subsolidus (Beglyarov, I960) Amhlyseius tenuis (Hirschmann, 1962) Amhlyseiuszwoelferi (Dosse, 1957) Phytoseius macropilis (Banks) P. macropilis was common on various deciduous trees and bushes. Together with E. finlandicus, it was one of the two most common species on apple tree. The two species often occurred on the same trees and even on the same leaves in equal numbers. P. macropilis occurred on leaves with high num- bers of tydeid and eriophyid mites, and lower num- bers of P. ulmi or tarsonemids (Table 3). Feeding studies on P. macropilis have shown that it developed more rapidly when fed P. ulmi or the astigmatid mite Czenspinskia lordi Nesbitt than on T. urticae. Tydeid mites were not suitable food at all (Dosse 1956). Herbert (1959) listed the following prey species for P. macropilis: P. ulmi, summer eggs, larvae, nymphs and adults; Bryohia arborea M. & A., summer eggs, nymphs and adults; Tetranychus telarius(L.), eggs and nymphs; A. schlechtendali, adults. In the laboratory studies of Kropczynska-Linkiewicz (1973), P. macro- pilis developed most rapidly when fed on A. schlechtendali (8.9 d), followed by P. ulmi (9.6 d) and T. urticae (10.3 d). All these diets resulted in the same egg-laying intensity (16.2-16.9 eggs/fe- male). Kozlowski and Kozlowska (1991) found that P. macropilis consumed 33.7 rust mites per day, twice as much as did E. finlandicus. The fecundity of P. macropilis was 7.1 eggs in 5 days period, about the same as that ofE. finlandicus. Amano and Chant (1990) found that P macropilis formed a rather simple and stable prey predator system in an abandoned orchard through- out a three-year research period. The available prey species consisted of tydeids, eriophyids and tetranychids; the other common phytoseiid in that orchard was E. finlandicus. P macropilis is important for the integrated con- trol of phytophagous mites on apple trees in Fin- land. It was relatively more common on unsprayed trees than on sprayed trees. This difference may be due to its locomotory habits, which may slow down its ability for aerial distribution and thus resettling of sprayed trees (III). The observation that P. macropilis is common on leaves with abundant hairs on the undersurface, and less common on plants with smooth leaves may also mean poorer chances for coincidental aerial distribution if the hairs arrest the animals (Collyer 1956). Paraseiulus soleiger (Ribaga) This species was widespread and sometimes oc- curred in high numbers. It was found on numerous deciduous trees and bushes, and on apple trees 18% of the phytoseiids belonged to this species. P. solei- geroccurred on unsprayed and, to some extent, also on sprayed trees. It was found on trees with relat- ively high numbers of tydeid mites but P. ulmi, A. 16 Agric. Sei. Fint. Suppl. No. 1 (1993) Table 3, Mites associated with phytoseiid species on apple trees. Based on observations on unsprayed apple trees in 1985-1989. - not observed; + observed occasionally, in low numbers; ++ observed regularly, in low or moderate numbers; +++ observed in high numbers Phytoseiid species P.ulmi Tydeid. Erioph. Tarson. Other phytoseiids 1 ’ Phytoseius macropilis + +++ +++ + All other species2* Paraseiulus soleiger + +++ +++ + All other species2* P. talhii - + + - P. soleiger P. macropilis P. triporus P. triporus + +++ + + P macropilis +++ E.finlandicus +++ P. soleiger +++ A. rhenanus + A. subsolidus + Anlhoseius bakeri + +++ +++ + P. macropilis E.finlandicus P. soleiger A. suecicus A. rhenanus - +++ - - P. macropilis +++ E.finlandicus ++ P. soleiger + A. reductus + A. suhsolidus + A. richleri + +++ + - P. macropilis +++ E.finlandicus +++ P. soleiger + A. suhsolidus + A. reductus + A. suecicus - + - - P. macropilis P. soleiger E.finlandicus A. viktorovi + + + - P. triporus Euseius finlandicus + +++ +++ + All other species3 * Amhlyseius reductus + +++ + - E.finlandicus +++ P. macropilis +++ P. soleiger ++ A. subsolidus + P. triporus + A. suhsolidus + +++ + - P. macropilis +++ E. finlandicus +++ P. soleiger + P triporus + A. rhenanus + A. rich!eri + A. reductus + '* In cases of only a few observation, only species list is given. If only single specimen of a spieces was found, it is omitted. 2 * Except A. viktorovi. 3 * Except A. viktorovi and P talbii. 17 Agric. Sei. Finl. Suppl. No. 1 (1993) schlechtendali and tarsonemids were also present (Table 3). According to Dosse (1956), P. soleiger is rather specialized, with tydeid mites being its main food source. It cannot complete its development if P. ulmi or T. urticae are the only food source. Because of its relatively high abundance, P. soleiger can be an important species on apple, although its prey consists mostly of mites other than P. ulmi. Anthoseius rhenanus (Oudemans) This species was found in abundance on strawberry and, in smalleramounts, on many trees and bushes, including apple trees. Herbert (1959) listed the following prey species for A. rhenanus: P. ulmi, summer eggs, larvae, nymphs and adults; B. arbo- rea, summer eggs, nymphs and adults; T. telarius, eggs and nymphs; A. schlechtendali, adults. In feeding tests, conducted by Kozlowski and Koz- lowska(1991), A. rhenanus consumed 32.7 apple rust mites per day, which was twice as much as was the consumption of E. finlandicus. On the eriophyid diet, the fecundity of A. rhenanus was also higher than that ofE.finlandicus, P. macropilis or T. pyri. Because of its scarce occurrence on apple trees, A. rhenanus did not appear to be important for the integrated control of mites on apple. Its role as natural enemy of spider mites, eriophyid mites, and the strawberry mite Phytonemus pallidus ssp. fra- gariae (Zimm.) is obviously more important on strawberry and other berry plants (Tuovinen 1992b). Typhlodromus pyri Scheuten This species was found in only one location in Åland, on black currant, and even there in low density. It is commonly used in integrated control programmes all over the world, especially because there are resistant strains to OP insecticides (Hoyt 1972). Because T. pyri has not been found on apple trees or any other trees in Finland it is possible that its relatively poor resistance to severe frost prevents it from overwintering on tree trunks or branches above the snow cover (MacPHEE 1963). The occur- rence of the species in Åland, where the climate is more favourable shows that there may be possibil- ities to the utilizationof the species in that area. In Norway, T. pyri is common on apple trees (Edland 1987). In the laboratory studies by Kropczynska- Linkiewicz (1973), T. pyri developed most rapidly when fed on T. urticae (9.5 d), followed by A. schlechtendali (10.4) and P. ulmi (10.9 d). A con- siderably longer development time was needed with Bryohia ruhriocolus (Scheuten) (13.7 d). The diets resulted in an egglaying rate of 7.1 (T. urticae) to 10.1 (P. ulmi) eggs per female. Kozlowski and Kozlowska (1991) found that T. pyri consumed 36.3 eriophyids per day, more than the consump- tion of other phytoseiids (e.g. P. macropilis, A. rhenanus and E.finlandicus). However, the fecund- ity of T. pyri was lower on the eriophyid diet than that of other phytoseiids. Resistant strains of T. pyri could be used in Fin- land as an introduced natural enemy. Introductions may have to be repeated, at least after hard winters. T. pyri is an interesting species, whose competence and importance may be increased by climatic change. Euseiusfinlandicus (Oudemans) This species was common and it was the most widely distributed species on deciduous trees and bushes. It has been recorded on numerous trees and bushes, less frequently on herbaceous plants, all over the world (de Moraes et al. 1986). Herbert (1959) listed the following prey spe- cies for E. finlandicus: P. ulmi, summer eggs, lar- vae, nymphs and adults; B. arborea, summer eggs, nymphs and adults; T. telarius, eggs and nymphs; A. schlechtendali, adults. In the laboratory studies of Kropczynska-Linkiewicz (1973), E.finlandi- cus developed most rapidly when fed on P. ulmi (7.6 d), followed by B. ruhriocolus (7.7 d), T. urti- cae (8.9 d) and A. schlechtendali (10.8 d). Spores and hyphae of the apple mildew Podosphaera leu- cotricha Ellis & Everh. appeared to be suitable food 18 Agric. Sei. Fin!. Suppl. No. 1 (1993) for E.finlandicus, and it developed and reproduced normally on this diet (10.7 d and 9.5 laid eggs/fe- male). The other diets resulted in an egg laying intensity of 7.2 (T. urticae) to 15.6 {A. schlechten- dali) eggs per female. DICKE et al. (1988) showed that E.finlandicus preferred A. schlechtendali to P. ulmi as food. Kozlowski and Kozlowska (1991) found that starving females of E. finlandicus con- sumed as many eriophyids as other phytoseiids (e.g. T. pyri, A. rhenanus, P. macropilis), but their normal consumption was significantly lower than that of other phytoseiids. Schausberger (1990) compared the pollen of various plants as a food source for E. finlandicus and found that birch and cherry pollen were satisfactory food for reproduc- tion. E. finlandicus was relatively more abundant in sprayed orchards than on unsprayed trees (Figs. 3 and 4). This pattern is attributed to its active mov- ing habits, which facilitate aerial distribution, rather than to its possible resistance to pesticides (III). On unsprayed apple trees, E. finlandicus can effect- ively control P. ulmi (Chant 1959, Gruys 1982, Sechser et al. 1984), but in sprayed orchards it is considered less important than other, resistant phy- toseiid species (Gruys 1982,Thistlewood 1991). Amano and Chant (1990) noted that E.finlandi- cus formed a stable population in a single un- sprayed apple tree, where, together with P. macropilis, it regulated phytophagous mite popula- tions. It is also common in Italian peach orchards, where it is regarded as an efficient natural enemy of P. ulmi. However, it is more sensitive to OP-pesti- cides than A. andersoni, which is common in Italy (Duso 1992). E.finlandicus is a competent species which is well adapted to different environmental conditions. It is an important predator of phyto- phagous mites on apple in Finland. Amblyseius reductus Wainstein This species was found on several species of trees, bushes and herbs. It occasionally occurred in rather high densities on apple trees, and was found on apple leaves inhabited by tydeid mites and, in lesser amounts, by eriophyids, P. ulmi and tarsonemids (Table 3). Tokunova and Malov (1988) used A. reductus to control spider mites on strawberry in Russia. Although A. reductus is not widely distrib- uted it may be relevant for the integrated control of mites on apple trees. Amblyseius subsolidus (Beglyarov) This species was found on apple trees, hawthorn and bird cherry. Although 4.5% of the phytoseiids on apple trees belonged to this species, it occurred only in a few localities. A. subsolidus was found on apple leaves inhabited by tydeid mites and, in lesser amounts, by eriophyids and P. ulmi (Table 3). A. subsolidus occasionally occurred in relatively high numbers on apple trees, and it can be an important species for the integrated control in some areas. 1.3 The role of phytoseiid mites on apple trees Unsprayed apple trees contain numerous species of mites at different trophic levels. In this study un- sprayed apple trees usually contained more than a single phytoseiid species, most often 2-4 species. The two most common species, P. macropilis and E. finlandicus, frequently occurred together, and both of them can be predominant species on apple (Figs. 3 and 4). In a comprehensive study of the occurrence of predatory mites and prey species in an apple orch- ard, Karg (1972) found negative correlations be- tween the number of predatory mites and prey mites, mainly P. ulmi and A. schlechtendali. The main species in his study was Typhlodromus tilia- rum (Oudemans), which is not found inFinland, but E. finlandicus was also present. The correlation between E. finlandicus and A. schlechtendali was more evident than that between the former and P. ulmi. T. tiliarum was the predominant species for the first two years and E. finlandicus in the third year. Karg (1972) concluded that if 50% of leaves were inhabited by predatory mites, spider mites would not be able to build up gradations. The obser- vations found in the present study that numbers of P. ulmi were very low if phytoseiid numbers ex- ceeded 0.5/leaf are consistent with his conclusion. 19 Agric. Sei. Finl. Suppl. No. 1 (1993) Many phytophagous and fungivorous mites serve as food sources for predatory mites. In Canada, Amano and Chant (1990) found 20 mite species occurring in an abandoned orchard, but, remarkably, no specimens of P. ulmi or T. urticae, the pest mites most common in commercial orch- ards in Canada. Instead, two other tetranychid spe- cies were present, with their highest density being 6 mites/leaf. Nine phytoseiid species were found, and three of them, E. finlandicus and P. macropilis in the abandoned orchard, and Typhlodromus pomi (Parrott) in a big isolated apple tree, occurred abun- dantly. There is considerable difference in species dominance in both sprayed and unsprayed trees between eastern and western North America (Amano and Chant 1990). In Finland, there are often marked differences in phytoseiid species compositions between differentapple tree individu- als even in the same locality. These differences may partly be due to the difference in leaf structures, such as to the degree of hairiness, between apple cultivars. Other factors, such as the presence of other predators and the availability of other food such as pollen may also affect the dominance and stability of the phytoseiid species. According to Walde et al. (1992), even when a specialist predator shows stronger numerical and functional responses to increases in its prey, a gen- eralist predator such as T. pyri, can be as effective as a specialist. Moreover, a generalist can survive even if its principal prey is exterminated. High predator-prey ratios are often needed to control spider mites at low prey densities. The major im- pact of the generalist phytoseiid may be at low prey densities on perennial crops such as apple, when population fluctuations are limited to low ampli- tudes (McMurtry 1992). The generalist phyto- seiids are probably not able to ’catch up’ from low predator-prey ratios to suppress therapidly increas- ing spider mite population. However, such an abil- ity has been noticed in A. andersoni vs. P. ulmi (Ivancich Gambaro 1986). Observations of the common Finnish generalist phytoseiids, E. fin- landicus and P. macropilis, show that theirpopula- tions can grow large in one season but that the suppression of a large P. ulmi population needs a longer period than one season, finally resulting in a high predator-prey ratio (Tuovinen, unpubl.). In natural conditions, this final situation is a result of many components, including natural enemies other thanphytoseiid predators (Chazeau 1985). The effect of a multi-species predator complex on a multi-species complex of phytophagous mites may be more stable than that of a single predator species, as the differences in prey and feeding habits can stabilize the prey-predator system. The unsprayed trees in this study were normally inhab- ited by 2-4 species of phytoseiids, which facilitate good adaptability to a changing prey complex. Croft et al. (1992) studied the effect of mixed populations ofM. occidentalis and T. pyri on three phytophagous mites. They found that control was as good as or better than with a single phytoseiid species. Therefore, a high diversity of phytoseiid species in and around orchards is generally an ad- vantage in the natural control of phytophagous mites. The interactions of E. finlandicus and P. macropilis were studied by Amano and Chant (1990), who found rather stable predatory mite populations in unsprayed apple tree habitats. Can- nibalism occurs among phytoseiids, and interspeci- fic predation is also probable, but these should be thought as a way of surviving rather than as a self-destructive habit (cf. Croft et al. 1992). A multi-species predator complex may tolerate pesti- cides better than a single-species system, even if no resistance occurs, because at the time of harmful spraying different species may be at different de- velopmental phases and thus may have different tolerance to pesticides. Furthermore, behavioural differences may also be important when tolerance to pesticides is concerned. These aspects need to be studied more precisely inFinnish conditions. The low density of phytoseiid mites noted on sprayed apple trees and the high density of P. ulmi show that the pesticide treatments normally applied in commercial orchards are destructive to all phyto- seiid species occurring in this country but have no, or only a small, effect on P. ulmi. Although the number ofinsecticide sprays harmful to phytoseiid mites is low in Finnish apple orchards, 2.1 - 3.7 per season (Tuovinen 1992a), it is enough to keep the phytoseiid density low. There is urgent need for insecticides that are safer to phytoseiid mites, and 20 Agric. Sei. Finl. Suppl. No. 1 (1993) also for better knowledge of spraying thresholds to avoid unnecessary sprayings (cf. Hesjedal 1990). OP-resistant phytoseiid strains have been widely used in IPM programmes, most commonly T. pyri in Europe and A. fallacis in North America. The presence of T. pyri in Åland shows that this species could be utilized in Finland, although it obviously needs to be introduced into apple orchards. The prospects offinding OP-resistant strains in our most common species, E. finlandicus, may be limited, because of the lower amount of detoxifying en- zymes, compared to those phytoseiids in which resistance occur (Sula and Zacharda 1991). Therefore, the recent finding of 5-fold differences between Finnish E. finlandicus colonies in resist- ance to azinphosmethyl and dimethoate is interest- ing (Tuomas Kostiainen, pers. comm.). Finding or breeding more resistant strains is important, and even a lower level of resistance could be satisfact- ory, especially if low concentrations of insecticide sprays can be applied (cf. Hesjedal 1990). 2 Surrounding vegetation as a source of phytoseiid mites Phytoseiid mites occurred on a wide range of host plants (I, II). The favoured host plants, or those on which more than 1 phytoseiid mite/leafwere found, include the following bushes and trees: Aesculus hippocastani, Aristolochia macrophylla, Corylus avellana, Fragaria vesca, Fraxinus excelsior, Juglans cinerea, Pterocarya rhoifolia, Ribes nig- rum, Ruhus odoratus, Sorbus aucuparia, S. thuringiaca, Tiliä x euchlora and Ulmus glabra. Owing to the shortage of samples in this study, the above plants are only examples of goodhost plants; the material does not permit their relative order in suitability as hosts to be calculated statistically. There are certainly many other trees, bushes and herbaceous plants which may be of great value as hosts for phytoseiid mites. However, phytoseiid mites were not found on the most common decidu- ous trees in Finland, Betula puhescens and B. ver- rucosa (III). The same two species, E. finlandicus and P. macropilis, that were common on apple trees were the most common on most of the other trees and bushes, too (II). Only Seiulus aceri (Collyer) was found to be strictly related to a certain host plant, Acer platanoides. Adjacent vegetation had some effect on the phy- toseiid densities and species compositions found on apple trees, although local differences were mean- ingful (III). Great differences in phytoseiid popula- tion size between individuals of the same host plant species can even occur in the same locality. Phyto- seiids usually occurred only occasionally in sprayed orchards with only a few good adjacent host plants but more abundantly in orchards sur- rounded by suitable host plants. P. macropilis was the predominant species on unsprayed apple trees, but E. finlandicus was more common in sprayed orchards. In general, this difference should not, however, be understood as resistance to pesticides in E. finlandicus populations but rather as better dispersing capacity (III). In a 2-ha orchard surrounded by deciduous trees and bushes, phytoseiid density was high (0.3- 3.1/leaf) only 15 days after a spraying with di- methoate (III). Phytoseiid mites were encountered in the vicinity of the orchard on the following trees and bushes: Prunus padus (0.3 mites/leaf), C. avel- lana (9.8/leaf),Lonicera xylosteum (2.7/leaf), Tiliä cordata (2.4/leaf), Quercus robur (1.2/leaf) and Salix caprea (0.8/leaf). In the same orchard, E. finlandicus was the dominantspecies on both apple trees and other host plants, with the exception of S. caprea, on which P. macropilis was dominant. Both E. finlandicus and P. macropilis were com- mon also on plants where spider mites were scarce (III). The capacity of phytoseiids for long-distance air- borne dispersal is obviously quite high, and smaller orchards or blocks may be rapidly recolonized after the application of harmful sprays if host plants inhabitedby phytoseiids are nearby. Tall trees, such as oak, lime and elm appear to be more important than low bushes as natural sources of phytoseiids in aerial dispersal (III). Hoy et al. (1985) noted that phytoseiid mites can disperse at least 200 m, prob- ably even further, via air turbulence. There are certainly differences in the dispersal capacity of phytoseiid species, due to their locomotory habits 21 Agric. Sei. Finl. Suppl. No. 1 (1993) and activity. An actively moving species such as E. fmlandicus obviously can migrate more rapidly from adjacent vegetation thanP. macropilis, which moves slowly and tends to hide under hairs. Relatively large numbers of phytoseiid mites, mainly E. finlandicus and P. macropilis, were found in samples with very few phytophagous mites (II). The availability of animal food is not a prerequisite for the occurrence of phytoseiid mites. The same was observed by Ivancich Gambaro (1988) in Italian fruit orchards in the case of Am- hlyseius aherrans Oudemans. Roller et al. (1988) studied hedges as a poten- tial source of phytoseiid mites and found that high densities ofT. pyri were regularly present on Rubus fruticosus, and lower densities on C. avellana, Cor- nus sanguinea and L. xylosteum. They concluded that hedges upwind of vineyards could act as sources of T. pyri provided a plant community of suitable composition was available. The same con- clusion is drawn from the present studies for E. finlandicus in Finnish apple orchards (11, III). The artificial introduction of phytoseiid mites into fruit orchards has been attempted on numerous occasions (Solomon 1986,Wildbolz and Staub 1986, Wildbolz 1988, Roller and Remund 1991). However, establishing a new phytoseiid community is not always a simple task. In France, Fauvel and Gendrier (1992) reported that the introduction of A. undersoni and T. pyri into vineyards with the aid of vine canes or branches of hackberry (Celtis australis) did not succeed. They presented several possible reasons for the failure: excessive susceptibility of the ’wild’ phytoseiid strain to the sprays still necessary; insufficient re- lease numbers; release at the wrong time; competi- tion of other phytoseiid species; too short duration of observations. However, none of the above reasons fully explained the failure; other climatic or environmental conditions might provide a more satisfactory explanation. In Hungary, Jenser et al. (1992) tried unsuccessfully to introduceE. finlandi- cus into an orchard treated only with harmless pes- ticides. They attributed the failure mainly to the lack of alternative food in the orchard. Under Finn- ish conditions, birch pollen, which is good food for E. finlandicus (Schausberger 1990), is available on apple leaves from early May to June-July, pro- moting the survival of immigrant phytoseiids. Natural immigration can lead to a rapid estab- lishment of phytoseiid mites in orchards sur- rounded by suitable host plants provided that the application ofharmful sprays is discontinued. This was recently observed in an experimental block of 0.5 ha which had earlier been sprayed with azin- phosmethyl and dimethoate but in which no harm- ful sprays were applied in 1991-1992. The phyto- seiid population, mainly E. finlandicus, but also P. macropilis, grew from zero to over 3/leafduring the first season after spraying was discontinued. An- other example is a young apple block of 100 trees planted in 1990 where small numbers of phyto- seiids were found only one year after planting (Tuovinen, unpubl.). The increasing diversity of plants around orch- ards can be hazardous because attacks by polyphagous pests such as the winter moth O. hru- mata or leaf miners can become more frequent (Wildbolz 1992). Therefore trees or bushes should not be conserved or planted near apple trees without careful consideration. The phytoseiid spe- cies composition on some trees and bushes is simi- lar to that on unsprayed apple trees, which should be seen as an advantage for using those plants (II). A good example of such a plant is hazel C. avel- lana. The effect of ground-cover plants in apple orch- ards on phytoseiid fauna was not studied in the present context. In Austria, Fischer-Colbrie and El-Rorolossy (1989) found phytoseiid mites on many herbs, e.g. Galeopsis, Lamium, Polygonum, Stellaria and Aegopodium, that are common weed species in Finland. The phytoseiid species found in their study are not the same as those found on apple trees in Finland but are the same as those on fruit trees in Austria. Phytoseiids can employ as food T. urticae, a species that is common on grasses, and pollen, which is available throughout the season. No phytoseiids were found in conventionally sprayed orchards but they were common in IPM or abandoned orchards (Fischer-Colbrie and El- Rorolossy 1989). It would be advisable to study the influence of ground-cover plants on phytoseiid mite numbers on apple in Finnish conditions, too. 22 Ague. Sei. Fint. Sappi. No. 1 (1993) 3 Pesticides in mite management In the course of the studies many observations were made on the effect of pesticides on predatory and phytophagous mites, e.g. in the chemical control studies (IV, V, VI), the surveys of phytoseiid spe- cies (II) and the study on the effect of surrounding vegetation (III). These observations are taken into account in the following evaluation ofselected pes- ticides. Ideally, acaricides should no longer be needed when integrated pest management methods are adopted. Therefore, acaricides should be consid- ered as a reserve measure, and should be applied only in the event of serious disturbances in the IPM system. They may have to be used at the start of IPM to lower the initial mite populations. Later, occasional pest problems may have to be controlled by broad-spectrum pesticides, which disturb the mite stability and may cause outbreaks of phyto- phagous mites. If only a very limited arsenal of efficient and ’phytoseiid-safe’ pesticides is avail- able, acaricides may be needed more frequently than if a higher number of selective pesticides were in use. 3.1 Acaricides In acaricide tests, chinomethionate, dicofol, fenbu- tatinoxide, mineral oil and oxydemetonmethyl were used as reference acaricides (IV, V). The use of dicofol has not been allowed since 1992, and chinomethionate is reported by advisors and grow- ers alike to be ineffective in many orchards. In control experiments, the reference acaricides were seldom as effective as the test acaricides, but in most cases, P. ulmi could be satisfactorily control- led by them, too, but two or even three treatments might be necessary (IV). The use of novel acaricides in the integrated control of phytophagous mites is evaluated briefly in the light of their effectiveness on target mites, and their influence on phytoseiid mites. As resist- ance in P. ulmi to clofentezine and hexythiazox has already been noticed (Thwaite 1991,REISSIG and Hull 1991), it is essential that they be used in integrated control only to lower initially high mite numbers and thus to assist phytoseiids and other predators to have better possibilities to maintain control. The real need for chemical control should therefore be carefully evaluated before treatment (CROFT et al. 1987). Mineral oils are not currently used in Finnish commercial apple orchards, mainly because, as ’weather sensitive’ pesticides, their effectiveness is not guaranteed. Pure paraffin oil is only slightly harmful to phytoseiid mites (Fischer-Colbrie and Elßorolossy 1988). 3.1.1 Flubenzimine Goodcontrol of P. ulmi was achieved with fluben- zimine when sprayed just before or during blossom and, if necessary, in late June or July. Later treat- ments resulted in a low overwintering population, facilitating mite control in the next season, too. Several applications in lower concentrations (25-85 g a.i./100 1 water) gave almost complete control of P. ulmi (IV). Flubenzimine was effective against A. schlech tendali(IV). SCHLIESSKE (1989) also found fluben- zimine to be effective against A. schlechtendali, but, in Germany, VOGT et al. (1990) found that a single spray of flubenzimine had only a temporary effect against A. schlechtendali. Flubenzimine was harmful to phytoseiid mites, and even one spray diminished numbers of E.fin- landicus and P. macropilis. When flubenzimine was sprayed several times during the season, phyto- seiids disappeared almost entirely (IV). ViGL et al. (1985) proposed that flubenzimine should not be used against P. ulmi because ofits harmful effect on the phytoseiid mites T. pyri and A. andersoni. Seier (1989) studied the effect of 500 ppm flubenzimine on females of A. andersoni and T. pyri, and found a 50% and 15% mortality, and a 63% and 54% reduc- tion in egg-laying intensity, respectively. Egg hatching was affected only slightly, but during the development of larvae and nymphs, the mortality rate was 75% and 47.5%, respectively. Hassan et al. (1991) rated flubenzimine as moderately harm- ful to E. finlandicus and T. pyri. Vogt (1992) sug- 23 Agric. Sei. Finl. Sappi. No. 1 (1993) gested that flubenzimine might have disturbed the development of predatory anthocorid larvae. Flubenzimine is an effective acaricide, but be- cause of its toxicity to phytoseiid mites and, pos- sibly, other natural enemies, it should not be used in the integrated control of P. ulmi. Exceptionally, it can be used to reduce the high initial density of both P. ulmi and A. schlechtendali before starting the integrated mite control. 3.1.2 Clofentezine Clofentezine was introduced as an ovo-larvicidal acaricide specifically for spider mite control (Bryan 1981). Laboratory tests showed that when sprayed on P. ulmi winter eggs early, that is, at the beginning of their spring development, clofen- tezine was more effective than when sprayed later. In field tests, clofentezine was effective when sprayed before the beginning of embryonic devel- opment of winter eggs (V). Marshall and Free (1991) achieved 100% mortality of young summer eggs and nymphs with a 25 ppm clofentezine con- centration, whereas not even 1000 ppm concentra- tion was toxic to adults. In laboratory tests con- ducted on peach leaves by Free et al. (1992), clofentezine retained its high effectiveness on sum- mer eggs ofP. ulmifor 10days, and some effective- ness for at least 30 days, suggesting that satisfactory control could be achieved with a single summer spray. When sprayed five times on trees with low den- sity populations of P. ulmi, in accordance with the apple scab spraying schedule, clofentezine signific- antly diminished the numbers of phytoseiid mites, but did not totally eliminate them (V). Repeated summer sprays affected the numbers of A. schlechtendali. Repeated sprays should be avoided because they may accelerate the development of resistance (cf. Marshall and Free 1991). Vogt (1992) found that one early spring spray had no effect on A. schlechtendali, but was successful against P. ulmi. In the UK, clofentezine suppressed A. schlechtendali to some extent but had littleeffect on the phytoseiid T. pyri, which kept eriophyid densities at a much lower level in clofentezine plots than in plots where phytoseiid numbers were greatly reduced (Easterbrook 1984). Seier (1989) studied the effect of 150 ppm clofentezine on the phytoseiid mites A. andersoni and T. pyri, and found no initial toxicity to females, but an almost 50% reduction in egg-laying intens- ity. Egg hatching was only slightly impaired, and the development oflarvae and nymphs was normal. Hassan et al. (1991) classified clofentezine as an acaricide harmless to phytoseiid mites and almost all other natural enemies included in the lOBC/WPRS working group’s testing programme. Clofentezine is an effective and relatively safe acaricide for integrated control on apple. It should be applied before P. ulmi winter egg hatching (V). 3.1.3 Hexythiazox Hexythiazox is toxic primarily to eggs and early nymphal stages of P. ulmi (Welty et al. 1988). In laboratory tests, 50 and 100 ppm hexythiazox di- minished the hatching of undeveloped P. ulmi win- ter eggs (92 and 99% effect, respectively), but the effect was poor when sprayed after the eggs had already started to develop. In field tests, hexythia- zox was effective when sprayed in spring during the winter egg hatching period (V). MARSHALL and Free (1991) achieved 100 and 79% mortality in young summer eggs with 1000and 25 ppm concen- trations, respectively, and 99% mortality in nymphs with a 25 ppm concentration. However, even a 1000 ppm concentration was not toxic to adults. Free et al. (1992) studied the persistence of the effectiveness of hexythiazox on summer eggs ofP. ulmi in the laboratory, and found that a good effect persisted for 20 days, and some effect for at least 30 days. The long-lasting effect of hexythiazox also in field conditions was found in the present study, where good control of P. ulmi was gained with a single summer spray (V). Repeated summer sprays did not have any effect on A. schlechtendali (V). In Germany, Vogt (1992) reported good control of P. ulmi and A. schlechtendali with hexythiazox sprayed early in the spring; however, the concentration of the spray was not given. When sprayed five times on trees with low dens- ity populations of P. ulmi, in accordance with the 24 Agric. Sd. Fint. Suppl. No. 1 (1993) apple scab spraying schedule, hexythiazox signific- antly diminished the numbers of phytoseiid mites but did not totally eliminate them (V). Hexythiazox is an effective acaricide against P. ulmi but not against A. schlechtendali. It is also relatively safe for phytoseiid mites (Bower 1990, Hassan et al. 1991, Vogt 1992). It can be used either during the egg hatching period in May, be- fore the adults have emerged, or in summer. Re- peated sprays shouldbe avoided to avoid the devel- opment of resistance (Thwaite 1991). 3.2 Insecticides As a rule, insecticide sprays are harmful to phyto- seiid mites but do not prevent an increase ofP. ulmi. If insecticides were used, with a few exceptions, the number ofphytoseiid mites wouldbe low but those of P. ulmi high, and, conversely, if no insecticide sprays were applied, the numbers of P. ulmi would be low, but phytoseiid mites would be found in almost every sample (11, III). The harmful effect of most insecticides on phy- toseiid mites is well known (Boller et al. 1989). Only a few phytoseiid species have been found to be resistant to the insecticides commonly used. T. pyri is the only species reported to be resistant that occurs in Finland, but it has not yet been found on apple trees (I). Even so, the possible resistance to most common insecticides in Finnish phytoseiid strains is worth to study. The recent finding of resistance to azinphosmethyl and dimethoate in E. finlandicus colonies is a good start for those studies (Tuomas Kostiainen, pers, comm.). In Norway, very low concentrations, 1/30-1/5 of the normal rates of the insecticides azinphosmethyl, fenitrothion and oxydemetonmethyl, are recom- mended for integrated plant protection in apple orchards, mainly to conserve predatory bugs, coc- cinellids and lacewings (Hesjedal 1990). How- ever, even such low concentrations may not save native phytoseiid populations, and an attempt is now being made to introduce OPresistant T. pyri strains in Norwegian orchards (Torgeir Edland, pers. comm.). The insect growth regulator (IGR) diflubenzuron is widely used in IPM programmes and is harmless to phytoseiid species (Kuijpers 1992). However, it has not been efficient enough against the apple fruit moth A. conjugella (Tuovinen, unpubl.). Therefore, other IGR and ICR (insect chitinsynthesis regula- tor) insecticides should be tested to find efficient but ’phytoseiid-safe’ insecticide against this key pest. As most of the samples were collected in August- September, the interval between harmful sprays and sampling date was quite long, usually more than one month. Most of the phytoseiid specimens found in sprayed orchards are thought to have originated from surrounding unsprayed vegetation. Therefore, the results of this study cannot be used to evaluate in detail the effect of different spraying programmes on phytoseiid mite densities. 3.3 Fungicides 3.3.1 Bitertanol In laboratory tests direct spray of 125 ppm biter- tanol had only a slight or non-significant effect on P. ulmi larvae; it had no effect on winter egg hatch- ing, either (VI). In a field experiment, four sprays withbitertanol in June-July caused a slight non-sig- nificant increase in numbers of P. ulmi, but did not affect Eriophyidae, Tydeidae or Phytoseiidae. In field tests, bitertanol was harmless to E. fin- landicus (VI). Seier(l9B9) found no initial toxicity with 125 ppm bitertanol to females ofA. andersoni and T. pyri, but the spraying caused about 50% reduction in egg-laying intensity. Egg hatching was only slightly reduced, and larvae and nymphs de- veloped normally. Hassan et al. (1991) rated biter- tanol as harmless to all tested natural enemies, ex- cept A. andersoni, on which it had a slightly harm- ful effect. Bitertanol appear to be safe in integrated control programmes in Finnish conditions. 3.3.2 Dichlofluanid In laboratory tests, 1000 ppm dichlofluanidsprayed on larvae of P. ulmi either killed them or prevented their further development. However, it had no ef- 25 Agric. Sei. Fint. Sappi. No. 1 (1993) feet on P. ulmi winter egg hatching (VI). Dichlofluanid reduced numbers and prevented egg laying of P. ulmi. It also had some effect on A. schlechtendali. It had an adverse effect on phyto- seiid mites (VI). Karg et al. (1973) showed that dichlofluanid is harmful to E. finlandicus. On the basis of field tests, Hassan et al. (1991) rated dichlofluanid as moderately harmful to the phyto- seiid mites A. andersoni and T. pyri. Although di- chlofluanid has an effect on P. ulmi and A. schlechtendali, it should not be used in integrated control programmes. Treatments shouldbe avoided especially if phytoseiid mites are present. 3.3.3 Dithianon In laboratory tests, dithianon had only a slight, statistically nonsignificant effect on P. ulmi larvae and no influence on winter egg hatching (VI). Four sprays with dithianon were harmless to the phytoseiid mites P. soleiger and A. suhsolidus (VI). Dithianon had no effect on the predatory mites T. pyri and A. andersoni (VIGL 1986). SEIER (1989) studied the effect of 500 ppm dithianon on the phytoseiid mites A. andersoni and T. pyri, and found only very low initial toxicity to A. andersoni females, and only a slight reduction in egg-laying intensity in both species. Egg hatching was not affected, and larvae and nymphs developed norm- ally. With the exception of a slight harmful effect on A. andersoni, Hassan et al. (1991) rated dithi- anon as harmless to natural enemies. In field tests, dithianon was harmless to E. finlandicus (VI). Dithianon appear to be safe in integrated control programmes in Finnish conditions. 3.3.4 Triforine In laboratory tests, 240 ppm triforine sprayed on larvae of P. ulmi either killed them or prevented their further development. Triforine caused 75% reduction in P. ulmi winter egg hatching when sprayed a few days before hatching. In a field ex- periment, four sprays with triforine in June-July temporarily reduced number of A. schlechtendali (VI). Four sprays with triforine had a detrimental ef- fect on numbers of phytoseiid mites, but, after the sprays, the phytoseiid mite numbers increased once more (VI). Boller et al. (1989) regarded triforine as harmless to T. pyri. In integrated control pro- grammes, triforine could be sprayed in spring, but continuous use should be avoided. SUMMARY AND CONCLUSIONS Knowledge of naturally occurring phytoseiid mites inFinland was poor until the first survey conducted in 1985 to establish the occurrence of phytoseiid species on apple trees. Before that, only two species had been recorded in Finland. Numerous studies in many countries have proven that phytoseiid mites are the most important natural enemies of the Euro- pean red spider mite Panonychus ulmi, the most harmful mite pest in Finnish apple orchards. The survey of phytoseiid mites showed that the same situation prevails in Finland, too. Twelve species belonging to eight genera of the family Phytoseiidae were found to occur on apple trees. The most common species are Euseius fin- landicus, Phytoseius macropilis and Paraseiulus soleiger. Of the other species, Amhlyseius suhsoli- dus and A. reductus occurred occasionally in relat- ively high densities, whereas Anthoseius rhenanus, A. suecicus, A. richteri, A. hakeri, A. viktorovi, Paraseiulus talbii and P. triporus occurred only occasionally and in low densities. The mean density of phytoseiid mites on un- sprayed trees was 1.2/leaf. In apple leaf samples from trees treated with pesticides, including at least one spray with organophosphorous insecticides, generally no or only a few phytoseiid mites were found. The most common species on sprayed apple trees were E. finlandicus, P. macropilis and P. soleiger, and their common densities in the treated trees were at most 0.2/leaf. The mean density of P. ulmi was 15 times higher on sprayed apple trees than on unsprayed trees. 26 Agric. Sei. Finl. Suppl. No. 1 (1993) Besides the species found on apple trees, eight other phytoseiid species were recorded on various other trees and bushes. Phytoseius juvenis, Seiulus aceri, Typhlodromuspyri, T. andrei, T. laurae, Pro- prioseiopsis okanagensis, Amblyseius zwoelferi and A. tenuis were reported as new species in Fin- land. T. pyri, which has been the subject of many investigations in integrated control programmes on apple, was found in only one location in Åland. This may be due to the low resistance to cold of this species. Phytoseiid density exceeded 1/leaf on several deciduous trees and bushes, e.g. Aesculus hip- pocastani, Corylus avellana, Fraxinus excelsior, Rihes nigrum, Rubus odoratus, Sorbus aucuparia, Tiliä spp. and Ulmus glabra, found around apple orchards and in forest margins. On average, the highest densities of the phytoseiids E. finlandicus and P. macropilis were recorded on the hazel C. avellana. Other common trees and bushes inhabited by phytoseiids, although less abundantly, were Crataegus coccinea, Prunus padus and Salix caprea. E. finlandicus occurred most commonly and in the highest densities, followed by P. macropilis, P. soleiger, P. triporus and A. rhe- nanus. The predominant species in these plants also inhabit unsprayed apple trees. The presence of prey mites, P. ulmi, the rust mite Aculus schlechtendali, or tydeid mites, was not a prerequisite for the occurrence ofphytoseiid mites. Relatively high densities of E. finlandicus and P. macropilis were found even when no prey mites at all were present. The above species are known to reproduce well without mite prey, e.g. by feeding on pollen or fungal rhizomes and spores. Experiments to control P. ulmi with specific acaricides were carried out in 1981-1989. An effective acaricide, flubenzimine, appeared to be harmful to the phytoseiids E. finlandicus and P. macropilis. Single treatments with clofentezine and hexythiazox, effective against P. ulmi, were harm- less to E. finlandicus and P. macropilis, but re- peated sprays ofboth acaricides reduced the density of phytoseiid mites. The effect of fungicides on P. ulmi and on phy- toseiidmites was also tested. Of the four fungicides used against the apple scab, dithianon and biter- tanol were rated harmless to phytoseiid mites, whereas dichlofluanid was harmful to phytoseiids. Triforine sprays initially reduced numbers of phy- toseiid mites, but later in the season the phytoseiid mites recovered and their density increased. Di- chlofluanid also affected P. ulmi, and triforine ap- peared to inhibit egg hatching in P. ulmi. The role of phytoseiid mites as natural enemies of P. ulmi in Finnish commercial apple orchards depends very much on the methods used to control insect pests. The use of less harmful pesticides and lower application dosages together with careful monitoring of the need for control would create better conditions for naturally occurring phytoseiid mites to survive and colonize apple trees. Phyto- seiid mite populations can be promoted by planting their favoured host plants around orchards and as windbreak hedges between blocks. Care is needed to avoid destroying phytoseiids by spraying during windy weather. Once established phytoseiid mites are generally capable of keeping phytophagous mite populations under the economic threshold. Many other natural enemies such as anthocorid bugs are also effective predators of spider mites, and should likewise be protected. Continuously high density of P. ulmi in an apple orchard is a signal that ecological damage has oc- curred, most likely due to intensive use of harmful pesticides. 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No. 1 (1993) SELOSTUS Phytoseiidae-heimon (Acari: Gamasina) petopunkit omenaviljelmillä ja niiden merkitys tuholaisina esiintyvien punkkien integroidussa torjunnassa Tuomo Tuovinen Maatalouden tutkimuskeskus Petopunkit tulivat Suomessa yleisesti tunnetuiksi vihannes- punkin biologisen torjunnan yhteydessä 1970-luvulla. Kuiten- kin jo 1930-luvulla tehtiin havaintoja petopunkkien esiintymi- sestä omenapuulla, ja jo silloin todettiin, että petopunkeilla voi olla huomattava merkitys hedelmäpuupunkin luontaisina vihollisina. Petopunkkilajit Suomessa ja niiden esiintyminen Tämän tutkimuksen yhteydessä määritettiin yhteensä 20 petopunkkilajia, joista 12 esiintyi myös omenalla. Kaksi lajia, Euseius finlandicus jaPhytoseius macropilis, olivat yleisiä ja käsittivät yli 70 % kaikista omenapuulla esiintyvistä petopun- keista. Samat lajit esiintyivät runsaslukuisina ja laajasti levin- neinä myös monilla muilla lehtipuilla ja pensailla. Muista omenalla esiintyvistä lajeista Paraseiulus soleiger oli yleinen ja paikoin runsaslukuinen, Amblyseius suhsolidus ja A. reduc- tus esiintyivät huomattavasti harvemmin, mutta kuitenkin eräillä alueilla kohtalaisen runsaslukuisina. Muut omenalla havaitut lajit, Anthoseius rhenanus,A. suecicus,A. richteri,A. bakeri, A. viktorovi, Paraseiulus talhii ja P. triporus olivat harvinaisia. Muilta kasveilta otetuissa näytteissä E. finlandicus ja P. macropilis olivat runsaslukuisimpia. Näytteitä kerättiin yh- teensä 47 kasvilajilta, joilla esiintyi omenalla todettujen lajien lisäksi 8 muuta petopunkkilajia: Phytoseius juvenis, Seiulus aceri, Typhlodromus andrei, T. laurae, T. pyri, Proprio- seiopsis okanagensis, Amblyseius tenuis ja A. zwoelferi. Useimmat näistä lajeista olivat harvinaisia, Petopunkkeja esiintyi säännöllisesti jarunsaasti mm. hevoskastanjalla, jala- valla, lehmuksella, pihlajalla, raidalla, saamella, tuomella sekä pensaista mm. pähkinäpensaalla, orapihlajalla sekä Rihes- jaRubus-lajeilla. Omenatarhan lähiympäristön kasvullisuuden havaittiin vai- kuttavan petopunkkien runsauteen omenapuilla. Eräässä ha- vaintotarhassa todettiin petopunkkien määrän kasvavan huo- mattaviksi pian haitallisten ruiskutusten jälkeen. Tarhan välit- tömässä läheisyydessä kasvoi mm. kookkaita lehmuksia ja tammia sekä pähkinäpensaita, joilla esiintyi runsaasti etenkin E. finlandicus -petopunkkia. Punkkien pääteltiin kulkeutuvan helposti tuulen mukana ympäröivistä puista japensaista ome- napuille. Hedelmäpuupunkin luontaista torjuntaa voidaankin edistää suojelemalla hyviä petopunkkien isäntäkasveja ja istut- tamallanäitä myös tuulensuojiksi. Ruiskutettaessa on varottava torjunta-aineenkulkeutumista näihin kasvustoihin. Torjunta-aineet ja petopunkit Hyönteisten torjunta-aineilla ruiskuttamattomissa ome- napuissa esiintyi elokuussa yhtä lehteä kohti keskimäärin 1,2 petopunkkia ja tavanomaisesti ruiskutetuissa puissa vain 0,05 petopunkkia. Hedelmäpuupunkkien osalta tilanne oli täysin päinvastainen: ruiskuttamattomissa tarhoissa määrä oli keski- määrin 1 punkki lehteä kohti ja ruiskutetuissa tarhoissa 15- kertainen. Ruiskutetuissa tarhoissa hedelmäpuupunkkien määrä oli huomattava vaikka tarhoissa oli suoritettu myös punkkien torjuntakäsittelyjä. Hedelmäpuupunkki lisääntyy etenkin lämpiminä jakuivina kesinä nopeasti ja voi alentaa huomattavasti omenasatoa. He- delmäpuupunkin torjunta on viime vuosina perustunut pääasi- assa kinometionaatin käyttöön, mutta toivottua tehoa ei lähes- kään aina saavuteta. Myös omenankellastajapunkki on viime vuosina paikoin yleistynyt. Lähes kaikki omenaviljelmillä käytettävät hyönteisten torjunta-aineet ovat haitallisia myös punkkien luontaisille vihollisille,petolUteille ja petopunkeille. Jatkuvasti suuri hedelmäpuupunkkien määrä omenatar- hasssa on osoitus siitä, että tarhassa vallitsee ekologisesti epävakaa tilanne, mikä lähes aina johtuu torjunta-aineiden runsaasta käytöstä. Koetarhoissa saatujen kokemusten mu- kaan tilanne voidaan saada hallintaan 1-3 vuodessa, mikäli petopunkeille ja muille luontaisille vihollisille haitallisiaruis- kutuksia voidaan vähentää ratkaisevasti. Tämän tutkimuksen yhteydessä testatut akarisidit, flu- bentsimiini, hexythiazox (’heksitiatsoksi’) ja klofentetsiini te- hosivat hyvin hedelmäpuupunkkiin. Flubentsimiini tehosi myös omenankellastajapunkkiin. Flubentsimiini oli kuitenkin haitallinen petopunkeille, sen sijaan klofentetsiini ja hexythia- zox olivat lähes haitattomia ja siten käyttökelpoisia myös integroidussa torjunnassa. Omenaruven torjunta-aineista diklofluanidilla ja triforiinil- la oli sivuvaikutus hedelmäpuupunkkiin ja omenankellastaja- punkkiin, mutta molemmat vaikuttivat haitallisesti myös pe- topunkkeihin. Bitertanoli ja ditianoni olivat haitattomia peto- punkeille. Kohti luontaista punkkien torjuntaa Tämän tutkimuksen yhteydessä saatujen kokemusten pe- rusteella voidaan suositella seuraavia toimenpiteitä, jotka so- veltuvat omenan integroidun tuotannon yhteyteen: 1) Käytetään kasvintuhoojien ja luontaisten vihollisten ha- vainnointi- ja arviointimenetelmiä torjunta-aineiden käytön 32 Agric. Sd. Fin!. Suppl. No. 1 (1993) 2 tarpeen selvittämiseksi. 2) Sovelletaan ohjekynnysarvoja ottaen huomioon luon- taisten vihollisten esiintyminen ja tarhan erityisolosuhteet. 3) Huolehditaan viljelyhygieniasta jakäytetään viljelytek- nisiä tai biologisia torjuntamenetelmiä silloin kun se on mah- doin ista. 4) Valitaan haitattomin mutta samalla riittävän tehokas torjunta-aine, käytetään alinta riittävän tehokasta liuosväke- vyyttä ja nestemäärää ja kohdistetaan ruiskutus havaintoihin perustuen oikeaan ajankohtaan. 5) Vältetään petopunkeille haitallisten torjunta-aineiden käyttöä erityisesti ennen kukintaa, talvehtineiden petopunk- kien lisääntymisen varmistamiseksi. 6) Varotaan torjunta-aineen ajautumista tuulen mukana lä- hiympäristön lehtipuihin ja pensaisiin. 7) Arvioidaan omenaruven torjunnan tarve varoituslaitteen avulla tai sään seurannan mukaan. Käytetään torjuntaan mie- luummin bitertanolia tai ditianonia kuin diklofluanidia tai triforiinia. 8) Säilytetään lähiympäristön kookkaat lehtipuut, kuten hevoskastanjat, lehmukset ja jalavat. Istutetaan tuulensuojiin pähkinäpensasta, raitaa ja muita petopunkkien suosimia puita ja pensaita. 9) Perustetaan erityinen petopunkkien kasvatusalue istutta- malla omenapuun taimia tihäksi kasvustoksi alueelle, jota ei käsitellä torjunta-aineilla. Siirretään kasvatustarhaan peto- punkkeja, joiden annetaan lisääntyä häiritsemättä. Kasvatus- alueelta voidaan petopunkkeja levintää vuosiversojen mukana omenatarhaan heinä-elokuussa, erityisesti mahdollisten peto- punkeille haitallisten ruiskutusten jälkeen. 10) Jos hedelmäpuupunkkien määrä on suuri, käytetään tehokasta valmistetta niiden määrän alentamiseksi ennen pe- topunkkien siirtämistä tarhaan. Fenbutatinaoksidi-, klofentet- siini- tai hexythiazox-valmisteiden haitallisuus petopunkeille on käytännössä vähäinen. Petopunkkien hyväksikäytön mahdollisuudet avomaaviljelyksillä Omenan lisäksi monet muut monivuotiset avomaaviljelyk- set kärsivät punkkien vioituksista. Petopunkkeja koskevaa tutkimusta kannattaa tulevaisuudessa kohdistaa erityisesti marjakasveilla esiintyvien haitallisten ja kemiallisesti vai- keasti torjuttavien punkkien kuten mansikkapunkin ja heru- kan äkämäpunkin luontaisen jabiologisen torjunnan kehittä- miseksi. Tämän tutkimuksen yhteydessä kertynyttä tietoa pe- topunkkien esiintymisestä eri kasveilla voidaan hyödyntää myös marjakasvien kasvinsuojelua koskevissa tutkimuksissa. Mikäli meillä esiintyvien petopunkkien kestävyttää hyön- teisten toijunta-aineita vastaan voidaan parantaa, avautuu pe- topunkkien hyväksikäytölle vielä paremmat mahdollisuudet. Toisaalta voidaan harkita resistenttien petopunkkikantojen tuontia maahan. Tällainen laji voisi olla T. pyri, jota yleisesti on käytetty Keski-Euroopassa. Myös uuden lajin tuontia voi- daan harkita, joskin epäonnistuminen on tällöin paljon toden- näköisempää. Petopunkkilajeista tunnetaan todennäköisesti vasta vain pieni osa, ja vain harvoista lajeista on olemassa perusteellista biologista tietoa. Meillä luonnossa esiintyvien lajien massa- kasvatus viljelyksille levittämistä varten voi myös tulla ajan- kohtaiseksi. Kasvatusmenetelmiä, jotka soveltuvat petopunk- kien avomaalle levittämistä varten ei ole vielä riittävästi tut- kittu. Myös tilakohtaisten petopunkkiviljelysten mahdollisuu- det tulisi selvittää. 33 Agric. Sei. Fin!. Suppl. No. 1 (1993) Agric. Sd. Finl. Suppt. No. 1 (1993) 34 I® Entomologiaa Fennica. 31.V. 1993 Identification and occurrence of phytoseiid mites (Gamasina: Phytoseiidae) in Finnish apple plantations and their surroundings Tuomo Tuovinen Tuovinen, T. 1993: Identification and occurrence of phytoseiid mites (Gamasina: Phytoseiidae) in Finnish apple plantations and their surroundings. Entomol. Fennica 4:95-114. Twelve species in eight generaof the family Phytoseiidae have been found to occur on apple trees and an additional eight species on various trees or bushes in their surroundings in Finland. Identification keys, supported by figures, are presented for 23 species, including three introduced species. The keys are based on published literatureand on the examinationofadult females collected in 1985-1991. The aim of thekeys and descriptions is to help non-taxonomist researchers with identification. Notes on the occurrence of the species on apple and other host plants in Finland are included. Tuomo Tuovinen, Institute ofPlantProtection, Agricultural Research Centre ofFinland, SF-31600 Jokioinen, Finland 1. Introduction Phytoseiid mites are known as effective natural enemies of spider mites (Tetranychidae) (Helle & Sabelis 1985). In Scandinavia, Hansen & Johnsen (1986), Edland (1987) and Karg & Ed- land (1987) have recently published records on Phytoseiidae. In Finland phytoseiid mites were observed to be natural enemies of the European red spider mite Panonychus ulmi (Koch) on apple trees as early as the 1930 s (Listo et al. 1939). Previous identification and reports of Phytoseiidae in Fin- land were made by Oudemans (1915), who de- scribed Euseius (Seiulus)fmlandicus (Oudemans) and identified Phytoseius macropilis (Seiulus spoofi) (Banks) on Salix sp. and later E. finlan- dicus on Prunus domestica, and by Athias-Henriot (ref. Moraes et al. 1986), who identified E. fm- landicus on P. domestica. No comprehensive data on phytoseiid mites were available subsequent to these notes until Kropczynska and Tuovinen (1987, 1988) reported on a study made in 1985. The material presented here proves that phytoseiid mites are common on the leaves of various wild and cultivated trees and bushes (Table 1). However, although at least twenty species occur naturally outdoors in Finland, only a few of them are common and widespread on a variety of host plants. E. fmlandicus, P. macro- pilis, and Paraseiulus soleiger (Ribaga) are so widely distributed and occur in such amounts that they can be expected to play important roles on apple trees (Table 2). Also the other species are considered to be important natural resources, although theirrelevance to the natural or biologi- cal control of pests needs further studies on dif- ferent host plants. As the value of phytoseiid mite species in integrated control is variable, correct diagnosis of the species is essential. Quite often, the same species from different regions have been de- scribed as different species by many authors. The terminology of the morphological features differs between authors, causing confusion for Table 1. List of host plants of Phytoseiidae in Finland. non-taxonomists. The aim of this study is to pro- vide keys for identification of the phytoseiid genera and species found in Finland, and update the data on the occurrence of phytoseiid mites in Finnish apple plantations and their surroundings. Host plant Phytoseiid species Acer platanoides Aesculus hippocastani Alnus glutinosa A. incana Amelanchierspicata Aristolochia macrophylla Betula lutea Cornus alba Corylus avellana Crataegus coccinea Fagus grandifolia Fragaria x ananassa F. vesca Fraxinus excelsior Juglans ailanthifolia J. cinerea J. mandschurica Lonicera xylosteum Matus domestica Prunus cerasus P. padus Pterocarya rhoifolia Pyrus communis Quercus robur Ribes nigrum R. rubrum R. uva-crispa Rubus fruticosus R. idaeus R. odoratus Salix caprea Salix sp Sorbus aucuparia S. thuringiaca Tiliä americana T. cordata T. euchlora Tussilago farfara Ulmus glabra Urtica dloica Viburnum opulus S. aceri, P. triporus, A. bakeri, A. richteri, E. finlandicus P. macropilis, P. triporus, E. finlandicus A. rhenanus E. finlandicus E. finlandicus E. finlandicus, A. reductus P. solelger, E. finlandicus E. finlandicus P. macropilis, P. solelger, P. triporus, E. finlandicus P. solelger, A. rhenanus, E. finlandicus, A. subsolidus P. macropilis, P. solelger, E. finlandicus P. macropilis, P. talbil, A. rhenanus, P. okanagensis, E. finlandicus, (A. cucumeris), A. reductus, A. tenuis, A. zwoelferi P. triporus, E. finlandicus, A. reductus P. solelger, E. finlandicus P. talbii, A. rhenanus, E. finlandicus P. solelger, A. rhenanus, E. finlandicus P. solelger, E. finlandicus P. macropilis, E. finlandicus, A. reductus P. macropilis, P. solelger, P. talbii, P. triporus, A. bakeri, A. rhenanus, A. richteri, A. suecicus, A. vlktorovi, (P. persimilis), E. finlandicus, A. reductus, A. subsolidus P. macropilis, P. triporus, A. rhenanus, E. finlandicus P. macropilis, P. triporus, E. finlandicus, A. subsolidus P. solelger, P. triporus, T. andrei, E. finlandicus E. finlandicus P. solelger, E. finlandicus P. macropilis, P. solelger, A. bakeri, A. rhenanus, T. laurae, P. okanagensis, E. finlandicus, A. zwoelferi P. macropilis, P. juvenis, P. triporus, A. bakeri, A. rhenanus, T. pyri, E. finlandicus, A. reductus P. triporus, E. finlandicus P. macropilis, E. finlandicus P. macropilis, P. juvenis, P. solelger, A. rhenanus, E. finlandicus, A. reductus P. triporus, E. finlandicus P. macropilis, E. finlandicus P. macropilis, P. solelger, E. finlandicus P. macropilis, P. triporus, A. richteri, A. rhenanus, E. finlandicus P. macropilis, P. solelger, E finlandicus P macropilis, E. finlandicus P. solelger, E. finlandicus P. solelger, E. finlandicus A. reductus P. macropilis, P. solelger, P. triporus, E. finlandicus, A. reductus E. finlandicus, A. reductus P. macropilis, E. finlandicus 96 Tuovinen: Phytoseiid mites in apple plantations • ENTOMOL. FENNICA Vol. 4 2. Materials and methods Phytoseiid mites were collected in southern Fin- land during 1985-1991 from sprayed and unsprayed fruit trees as well as other deciduous trees and bushes, in forest margins or nearby apple plantations. A normal leaf sample consisted of 100 leaves taken from a few plants at the same locality. The material used in this study included 270 leaf samples of 48 plant species. The leaves were either inspected under a stereomicroscope or they were first soaked in hot (65-70°C) soapy water for one day and then sieved to extract mites. Phytoseiid mites were then stored in 70% alcohol before mounting. Mites were mounted using a mediumprepared as follows: fine grinded, purified gum arabic, 50 g, and distilled water, 50 ml, are mixed carefully; the mixture is then preserved for 3—4 days in a closed bottle at +35°C, and after that chloral- hydrate, 125 g, and glycerol, 30 ml, are added and mixed in. After 10days preservation at+35°C the mixture is usable. The specimens were mac- erated in 70% lactic acid and then washed in alcohol before mounting. The cover slides were sealed with nail polish. Mites were examined using 250-500 x mag- nification. The lengths of the idiosoma, dorsal Table 2. Relative abundance (%) of phytoseiid mite species on apple leaf samples and number of samples including the species in 1985 and 1989. Species Samples 1985 1989 1985-89 Euseius finlandicus 31.5 45.4 70 Phytoseius macropilis 37.0 28.9 60 Paraseiulus soleiger 25.5 12.6 4125.5 12.6 41 Amblyseius subsolidus 3.2 10.0 13 Amblyseius reductus 1.6 0.9 131.6 0.9 13 Anthoseius rhenanus 0.0 1.3 7 Paraseiulus triporus - 0.8 8 Anthoseius suecicus 0.8 0.0 2 Anthoseius richteri 0.2 0.1 6 Anthoseius baker! 0.2 - 1 Paraseiulus talbii - 0.0 10.0 1 Anthoseius viktorovi - 0.0 1 Total individuals/samples 1920 2474 105 setae and the longest macroseta on leg IV were measured. The figures were drawn from micro- photographs taken from representative speci- mens. 3. Species of Phytoseiidae Phytoseiids are free-living, terrestrial mites and they occur on foliage, bark, and humus in all parts of the world (Chant 1985). The following description is based on Chant (1985). Phytoseiids are 300-500 (im long, their bodies are divided into two major parts, the gnathosoma, which includes the chelicerae and palps, and the idiosoma, to which the four pairs of legs are attached (Fig. IB). The idiosoma is covered by an undivided dorsal shield, which may be smooth or sclerotized and sculptured or reticulated. The dorsal shield bears at most 20 pairs of setae, excluding the sublateral setae, which may also be situated on the dorsal shield (in Phytoseius) (Fig. 1A). There are 2 pairs of sublateral setae, r 3 and R 1 (in Finnish genera). Ventrally, phytoseiids have three sclerotized shields: the sternal shield, genital shield and ventrianal shield(Fig. IB). The ventrianal shield bears pairs of setae anterior to the anus (preanal setae), a pair of para-anal setae on both sides of the anus and a single postanal seta. The shape of the ventrianal shield is variable. The gnathosoma is used for capturing and eating prey, and in the male also for copulation. The female chelicera consists of a fixed digit and a movable digit (Fig. 2B). There are several teeth on the fixed digit and fewer on the movable digit. The male chelicera has a fleshy spermato- dactyl (Fig. 2C), which transfers spermatophores from the genital opening to the female sperm induction pore. The spermatophore is then trans- ferred via a major duct to the spermatheca and into the cervix (Fig. 2A). Adult males are usually smaller than females. Their dorsal setae are in most cases arranged as in females, but they differ in shape of ventrianal shieldand in form ofchelicerae. Phytoseiid larvae have only three pairs of legs.Larvae and nymphal stages are smaller and they have fewer setae on the dorsal shield than adults. 97ENTOMOL. FENNICA Voi. 4 • Tuovinen: Phytoseiid mites in apple plantations 3.1. Keys and descriptions The identification keys for females have been worked out using the mite specimens collected to determine the characteristics of the species. The descriptions and keys of Chant (1957, 1959, 1965),Chant & Hansell (1971), Chant & Yoshida- Shaul (1982, 1987), Dosse (1958), Karg (1970, 1971, 1982, 1983, 1991), Beglyarov (1981), and Miedema (1987) have been used as reference guides for keys. The main synonyms are from the above references and from Moraes et al. (1986). Chant & Yoshida-Shaul (1986) divided the family Phytoseiidae into four subfamilies, Phytoseiinae, Amblyseiinae, Chantiinae, and Cydnodromellinae. This division is used in the following keys. The European phytoseiids be- long to the subfamilies Phytoseiinae and Amblyseiinae (Evans 1987). In the keys to subfamilies and genera, the concepts ofEvans (1987), based mainly on Karg (1983), have been followed, except that the genus Amblyseius Berlese also includes here the genera Neoseiulus Hughes and Typhlodromips De Leon. The genus Anthoseius De Leon is presented as a separate genera in Karg (1983), and this concept is followed here. The keys to genera are based primarily on the presence and relative lengths of dorsal setae and on the shape of the ventrianal shield and the number of setae on it (Fig. IA, B). For the identi- Fig. 1. Scheme of adult female phytoseiid. —A. Dorsal shield with terminology and locations of dorsal setae and main pores, ant. = anterior part of dorsal shield (proscutum); post. = posterior part of dorsal shield (postscutum); pe = peritreme; so= solenostome; st. = stigma. Setal nomenclature: jl = verticals; j3, z2, z3, z4, s4, s 6 = prolateral setae; j4, j5, j6, J 2 = dorsocentral setae; z5, z 6 = promediolateral setae; Zl, S2, S4, S5, Z 5 = postlateral setae; Z3, Z 4 = postmediolateral setae; J 5 = clunals. (Z 3 are situated anterior to Z4; if Z 3 are present, Zl or s 6 are missing). B. Ventral view with terminology and locations of diagnostic characteristics, ch = chelicera; gen.sh = genital shield; st.sh = sternal shield; va.sh = ventrianal shield, an = anus, po = pore on ventrianal shield; leg IV: coxa, trochanter, femur, genu, tibia, basitarsus, tarsus, m.s. = macroseta; mp = metapodal plates; sp = spermatheca. Setal nomenclature: JVI, JV2, JV3, JV4, JVS = medial setae; ZVI, ZV2, ZV3 = mediolateral setae; PA = para-anal setae; PST = post-anal seta. 98 Tuovinen: Phytoseiid mites in apple plantations • ENTOMOL. FENNICA Vol. 4 fication of the species the number ofsolcnostomes or pores on the dorsal shield and the presence of pores on the ventrianal shield, and the shape of the spermatheca (Fig. 2A) has to be considered. Other characteristics, the presence of macrosetae on the basitarsus, tibia and genu of leg IV (Fig. IB), the number of setae on the genu of leg 11, the extension of the peritremes (Fig. 1 A), and the number of teeth on the movable digit of the chelicerae (Fig. 2B) are used only occasionally in the keys. The mean, minimum and maximum of 10-20 measurements are presented, ifenough specimens have been available. The keys to gen- era and species are valid only for the included species. Different terminologies of the dorsal setae have been used by various authors, and that of Rowell et al. (1978) is adopted here (Table 3). Key to genera (females) of Phytoseiidae 1. 6 pairs (j3, z2, z3, z4, s4, s6) ofprolateral setae present (Phytoseiinae) 2 4 pairs (j3, z2, z4, s4) of prolateral setae present (Amblyseiinae) 6 2. Some dorsal setae, especially s4, s6, Z 4 and Z 5 thick and thorn-like; S2, S 4 and S 5 absent; J 2 absent; r 3 on dorsal shield; Rl absent Phytoseius, p. 100 Table 3. Comparison of setal terminology for dorsum of idiosoma in the descriptive taxonomy of Phytoseiidae. Row = Rowell et al. 1978, Karg = Karg 1971, 1981, Beg = Beglyarov 1980, Kol = Kolodochka 1984, Den = Denmark et al. 1984. Setae Row Karg Beg Kol Den Anterior dorsocentral j 1 il Dl D 1 V j 3 I 2 L 1 AMI LI j 4 13 D 2 D 2 D 1j 5 i 4 D 3 D 3 D 2 j 6 i 5 D 4 D 4 D 3 mediolateral z 2 s 2 L 2 ALI L 2z 3 s 3 L 3 AL2 L 3 z 4 zl L 4 AL3 L 4z 5 z 2 AM AM2 Ml z 6 z 3 - AM3 - lateral s 4 s 5 L 5 AL4 L 5 s 6 s 7 L 6 ALS L 6 marginal r 3 r 5 AS AS S 1 Posterior dorsocentral J 2 I 2 D 5 D 5 D 4 mediolateral J 5 I 5 D 6 D 6 C 1 Z 1 Z 1 - ML M 2 Z 3 Z 3 - PMI - Z 4 Z 4 PM PM2 M 3 Z 5 Z 5 PL PM3 LlO lateral S 2 S 2 L 7 PLI L 7 54 S 4 L 8 PL2 L 8 55 S 5 L 9 PL3 L 9 marginal Rl Rl PS PS S 2 Fig. 2. Diagnostic characters of adult phytoseiid mite. A. Spermatheca. B. Female chelicera. C. Male chelicera. 99ENTOMOL. FENNICA Voi. 4 • Tuovinen: Phytoseiid mites in apple plantations s 4 and s 6 never thick and thorn-like; 1-3pairs ofsetae S 2, S 4 and S 5 present; J 2 present; r 3 not on dorsal shield; R 1 present 3 3. Z 1 present Seiulus, p. 100 Z 1 absent 4 4. S 5 present 5 S 5 absent Typhlodromus, p. 103 5. z 6 present, additionally Z 3 may be present; JV2 ab- sent Paraseiulus, p. 101 z 6 and Z 3 always absent; JV2 present.. Anthoseius, p. 102 6. J 2 absent 7 J 2 present 8 7. j 6 long (>lOO pm), equal to about one half of the width of the dorsal shield; S 4 absent; preanal setae absent Phytoseiulus, p. 104 j 6 short (ca. 10 pm); S 4 present; 2or 3 pairs ofpreanal setae Proprioseiopsis, p. 104 8. 3 pairs of preanal setae arranged in a ‘zigzag’ row on anterior part of ventrianal shield Euseius, p. 105 3 pairs of preanal setae on ventrianal shield not ar- ranged as above Amblyseius, p. 105 Genus Phytoseius Ribaga Key to species 1. s 4 considerably longer than other dorsal setae; s4:s6 = ca. 1.4 macropilis s 4 about as long as s 6 juvenis Phytoseius macropilis (Banks) Fig. 3 Sejus macropilis Banks; Phytoseius (Seiulus) spoofi (Oudemans), Nesbitt; Typhlodromus macropilis (Banks), Westerboer & Bernhard; Dubininellus macropilis (Banks), according to Karg (1991). Diagnosis: Idiosoma 341 pm (320-368). Dorsal shield pale, variably sclerotized and heavily sculptured. Ventrianal shield smooth, usually with 2-3 pairs of preanal setae (or unpaired 2+3,1+3 or I+2). Shape of spermatheca variable, but always with a wide base, cervix only partly sclerotized, not always easily detect- able. Movable digit of chelicerae has 1 tooth. Lobe-ending macrosetae (85 pm, 72-96) present on tibia of leg IV, and much shorter macrosetae on genu and basitarsus. Distribution and host plants; Common on deciduous trees and bushes; found on Aesculus, Corylus, Fagus, Fragaria, Malus, Prunus, Ribes, Ruhus, Salix, Sorbus, Tiliä, Ulmus and Vibur- num. After E. fmlandicus, P. macropilis was the commonest species on apple trees. It has been recorded on numerous deciduous trees and bushes and some herbaceous plants from Europe, Asia and North and South America (Moraes et al. 1986). Phytoseius juvenis Wainstein & Arutunjan Fig. 4 Dubininellus juvenis (Wainstein & Arutunjan), according to Karg (1991). Diagnosis: Idiosoma 325 pm (310-340). Dorsal shield pale, variably sclerotized and heavily sculptured. Ventrianal shield smooth, with 1-2pairs of preanal setae (or unpaired 2+l, o+l or 2+3). Spermatheca wide with a bowed neck. Movable digit of chelicerae has 1 tooth. Lobe- ending macrosetae (93 pm 84-112) on tibia of leg IV and shorter macrosetae on genu and basitarsus. Distribution and host plants: Found on Ribes rubrum in Kokemäki (61°16'N, 22°15'E) and on Rubus idaeus in Åland (60°15'N, 19°58'E). P. juvenis has been recorded on fruit trees and berry plants in Eastern Europe (Karg 1991). GenusSeiulus Berlese Seiulus aceri (Collyer) Fig. 5 Typhlodromusaceri Collyer; Typhloctonus aceri (Collyer), according to Moraes et al. (1986). Diagnosis: Idiosoma 328 pm (320-336). Dorsal shield reticulated and sclerotized, with 3 pairs of small solenostomes. Ventrianal shield rectangular, with 4 pairs of preanal setae, and with none or 1 pair of small pores. Spermatheca with a long neck. Movable digit ofchelicerae has 1 small, hardly visible tooth. No macrosetae on leg IV. Distribution and host plants: Found only on Acerplatanoides. S. aceri is specialized in regard to its hostplants. It is recorded from Acer platanoides, A. campestre, Corylus sp., Cerasus 100 Tuovinen: Phytoseiid mites in apple plantations • ENTOMOL. FENNICA Vol. 4 sp. Juglans sp., Prunus sp., Rubus sp. and Zelkova sp. in Europe and Asia (Moraes et ai. 1986). Genus Paraseiulus Muina Key to species 1. Z 3 present talbii Z 3 absent 2 2. Dorsal shield without prominent pores; spermatheca narrow, bowed horn-shaped soleiger 3 pairs of prominent pores on dorsal shield; sperma- theca with wide cervix triporus Paraseiulus talbii (Athias-Henriot) Fig. 6 Typhlodromus talbii Athias-Henriot; Paraseiulus sub- soleiger Wainstein, Karg; Typhlodromus tetramedius Zaher & Shehata, Chant & Yoshida-Shaul; Seiulus amaliae Ragusa & Swirski, Chant & Yoshida-Shaul; Paraseiulus ostiolatus Athias-Henriot, Chant & Yoshida-Shaul; Bawus talbii (Athias-Henriot), ac- cording to Moraes et al. (1986). Diagnosis: Idiosoma 381 pm (356-400). Dorsal shield distinctly reticulated and strongly sclerotized, especially in posterior part, with 3 pairs of distinct, invaginated solenostomes. Ven- trianal shield narrow, ‘slipper-shaped’, sparsely striated, with 2 pairs ofpreanal setae. Spermatheca cervix wide, vase-shaped. Movable digit of chelicerae without teeth. No macrosetae on leg IV. Note: One female missing setae z 6 was found on wild Malus sp. In Paraseiulus some variation in number of dorsal setae has been noted earlier (Chant & Yoshida-Shaul 1989). Distribution and host plants: Found on Fragaria x ananassa, Juglans ailanthifolia, Malus sp. P. talbii has previously been recorded in Europe and Asia from many trees and bushes, including fruit Pees (Moraes et al. 1986). Paraseiulus soleiger (Ribaga) Fig. 7 Seiulus soleiger Ribaga; Typhlodromus soleiger (Ribaga), Nesbitt; Paraseiulus incognitus Wainstein & Arutun- jän, 1967, Chant & Yoshida-Shaul; Typhlodromus trimediosetus Xin, Liang & Ke, Chant & Yoshida- Shaul. Diagnosis: Idiosoma 324 jam (304-364). Dorsal shield strongly sclerotizedand reticulated. Ventrianal shield weakly striated or reticulated, with 2 pairs of preanal setae. Spermatheca long, hom-shaped. Movable digit of chelicerae with- out teeth. No macrosetae on leg IV. Note: A few females missing setae z 6 were found (less than 1 % of the material collected). Males ofP. soleiger always lack setae z6. Distribution and host plants: Widespread, occasionally in large numbers, found on Betula lutea, Corylus avellana, Crataegus coccinea, Fagus grandifolia, Fraxinus excelsior, Juglans cinerea, J. mandshurica, Malus sp., Pterocarya rhoifolia, Quercus robur, Ribes nigrum, Rubus idaeus, Sorbus thuringiaca. Tiliä cordata, Tiliä X euchlora, Ulmus glabra. P. soleiger has been recorded on numerous trees and bushes, and also in litter and grass, from Europe, Asia and North America (Moraes et al. 1986). It preys especially on tydeid mites (Dosse 1956). Paraseiulus triporus (Chant & Yoshida-Shaul) Fig. 8 Typhlodromus triporus Chant & Yoshida-Shaul. Diagnosis; Idiosoma 390 pm (360-408). Dorsal shield strongly sclerotized and reticulate, with 3 pairs ofdistinct, invaginated solenostomes. Ventrianal shield lightly striated, with 2 pairs of preanal setae. Spermatheca variable in shape, weakly sclerotized. Movable digit of chelicerae has 1 tooth. No macrosetae on leg IV. Note: One specimen with a single seta J 1 between J 2 and j6 was found. Distribution and host plants: Found in Finland on Acer platanoides, Aesculus hippocastani, Corylus avellana, Fragaria vesca, Malus sp., Prunus avium, Prunus padus, Pterocarya rhoi- folia, Ribes rubrum, Ribes uva-crispa, Sorbus aucuparia, Rubus odoratus, Ulmus glabra. P. triporus has previously been reported from Eu- rope and North America on many orchard trees, as well as other deciduous trees and bushes (Moraes etal. 1986). 101ENTOMOL. FENNICA Voi. 4 • Tuovinen: Phytoseiid mites in apple plantations GenusAnthoseius De Leon Key to species 1. Ventrianal shield with 3 pairs of preanal setae 2 Ventrianal shield with 4 pairs of preanal setae 3 2. Movable digit with 2 teeth; genu II with 6 setae; no distinct macrosetae on basitarsus IV; distinct pores close to S 5 viklorovi Movable digit with 1 tooth; genu II with 7 setae; macrosetae on basitarsus IV ending in a small lobe; distance of pores from the base of S 5 about the same as the length of S 5 suecicus 3. Spermatheca cilinder-shaped; movable digit with 1 tooth rhenanus Spermatheca with long cervix; movable digit with 2or 3 teeth 4 4. Ventrianal shield widest anteriorly; movable digit with 2 teeth richteri Ventrianal shield widest medially; movable digit with 3 teeth bakeri Diagnosis: Idiosoma 387 pm (380-392). Dorsal shield lightly reticulate and sclerotized, with variable number of pores, of which 3 pairs are distinct. 3 pairs ofpreanal setae on ventrianal shield (or unpaired 2+3), 1 pair ofpores. Sperma- theca cup-shaped, with a short atrium. Movable digit of chelicerae has 1 tooth. Hardly differenti- ated, lobe-ending macrosetae (25 pm, 24-28) on basitarsus on leg IV. A. suecicus and A. gilvus (Wainstein) are proposed as synonyms (Eiko Shaul, pers. comm. 1989). Distribution and host plants: Found only on Malus domestica in Mietoinen (60°47'N, 21 °24'E) and Pälkäne (61°47'N, 24°12'E). A. suecicus has previously been recorded on grass in Sweden, and on bird cherry in Yaroslavl, Russia, where it was described as A. gilvus (Moraes et al. 1986). Anthoseius viktorovi Wainstein Fig. 9 Amblydromella viktorovi (Wainstein), according to Moraes etal. (1986). Diagnosis: Idiosoma 370 pm. Dorsal shield lightly reticulated and sclerotized, with 4-5 pairs of pores, 3 distinct ones, one pair close to setae S5. Three pairs of preanal setae and one pair of faint pores on ventrianal shield. Shape of spermatheca conical. The movable digit of chelicerae has 2 teeth. No macrosetae on leg IV. Distribution and host plants: Only one female was found on Malus domestica, Pälkäne (61°20'N, 24°12'E). A. viktorovi has previously been recorded on pine in Yaroslavl Province, Russia (Moraes et al. 1986). Anthoseius suecicus (Sellnick) Fig. 10 Neoseiulus suecicus Sellnick; Typhlodromus suecicus (Sellnick), Karg; Amblydromella suecica (Sellnick), according to Moraes et al. (1986); Typhlodromus gilvus Wainstein (E. Shaul in litt.). Anthoseius rhenanus (Oudemans) Fig. 11 Seiulus rhenanus Oudemans; Typhlodromus foenilis Oudemans, Chant; Typhlodromus (Neoseiulus) rhenanus (Oudemans), Nesbitt; Typhlodromus kazachstanicus Wainstein, Chant; Amblydromella (Seiulus ) rhenana (Oudemans), according to Moraes et al. (1986). Diagnosis: Idiosoma 323 pm (312-328). Dorsal shield reticulate and sclerotized, with 3 pairs of small indistinct pores. Setae Z5, Z 4 and S 5 faintly serrated. Usually 4 pairs of preanal setae and 1 pair of small, sometimes invisible pores on ventrianal shield. Spermatheca cylin- drical. Movable digit of chelicerae has 1 tooth. Slightly differentiated macrosetae (29 pm, 25- 32) on basitarsus on leg IV. Distribution and host plants: Found on Alnus glutinosa, Crataegus coccinea, Fragaria x ana- nassa, Juglans ailanthifolia, Malus sp., Prunus avium, Ribes nigrum, R. rubrum, Rubus idaeus, Sorbus aucuparia. A. rhenanus has been re- corded on numerous trees, bushes and herba- ceous plants in Europe, Asia and North America (Moraes et al. 1986). In the present study, A. rhenanus occurred commonly on unsprayed strawberries. 102 Tuovinen: Phytoseiid mites in apple plantations • ENTOMOL. FENNICA Vol. 4 Anthoseius richteri (Karg) Fig. 12 Typhlodromus richteri Karg; Amblydromella (Typhlo- dromus richteri (Karg), according to Moraes et ai. (1986). Diagnosis: Idiosoma 432 |4m (416-464). Dorsal shield distinctly sclerotized and sculp- tured, with 4 pairs of pores, sometimes hardly visible. Dorsal setae relatively thick and stiff, setae Z5, Z 4 and S 4 faintly serrated. Ventrianal shield widest in anterior part, with 4 pairs of preanal setae and 1 pair of pores. Spermatheca funnel-shaped with a long, narrow, often bowed neck. Movable digit of chelicerae has 2 teeth. Macrosetae (44 pm, 40-46) on basitarsus of leg IV. In the description of A. richteri there are Z 1 instead of S 2 setae (Karg 1970). However, this type ofpattern is not listed in the setal patterns presented by Chant & Yoshida-Shaul (1989). Distribution and host plants: Found on Acer platanoides, Malus domestica and Sorbus aucu- paria. A. richteri has been recorded on deciduous trees in Central Europe and in Norway (Karg & Edland 1987, Karg 1991). Anthoseius bakeri (Garman) Fig. 13 Seiulus bakeri Garman; Typhlodromus bakeri (Garman), Nesbitt; Amblydromella ( Seiulus) bakeri (Garman), according to Moraes et al. 1986. Diagnosis: Idiosoma 402 pm (328-480). Dorsal shield heavily sclerotizedand sculptured, with no distinct pores. Setae Z 5 serrated. Ventrianal shield widest in medial part, with 4 pairs of preanal setae and a pair of faint pores (not always visible). Spermatheca hom-shaped, with a long and narrow atrium. Movable digit of chelicerae has 3 teeth. Macrosetae (34 pm, 31- 40) on basitarsus of leg IV. Distribution and host plants: Found on Malus sp., Ribes nigrum and R. rubrum. A. bakeri is a bark inhabiting species, and may be more com- mon on apple than the leaf samples show (Karg 1991). It has been recorded on numerous trees and bushes in North America, Europe, Asia and Australia (Moraes et al. 1986). Genus Typhlodromus Scheuten Key to species 1. 4 pairs of prominent pores on dorsal shield; 1 pair of pores anterior toZ 4 2 3 pairs of pores on dorsal shield; no pores anterior to setaeZ 4 pyri 2. Peritremes extend forward between j 3 and z2; spermatheca spur-shaped; Z 5 about twice as long as setaeZ 4 laurae Peritremes extend forward to the level of z4; sperma- theca wide V-shaped funnel without neck; Z 5 only slightly longer than Z 4 andrei Typhlodromus pyri Scheuten Fig. 14 Diagnosis: Idiosoma 342 pm (336-348). Dor- sal shield lightly sclerotized and distinctly reticu- lated, with 3 pairs of prominent solenostomes, but no pores anterior to setae Z4. Setae Z 4 and Z5 slightly serrated. Ventrianal shield with four pairs of preanal setae (20 pm). Spermatheca bell-shaped. Movable digit ofchelicerae has 2 teeth. Macrosetae (38 pm, 36-40) on basitarsus of leg IV. Distribution and host plants: Found only in Åland (60°15'N, 19°58'E) on red currant Ribes rubrum and black currant R. nigrum. T. pyri is widely used in the biological control of spider mites in orchards. As T. pyri has not been found on apple trees nor on other trees in Finland it is possible that it cannot overwinter here on trees. The occurrence of the species on currants in Åland, where the climate is more favourable than on the mainland, support this conclusion. In Norway, T. pyri occurs commonly on apple trees (Edland 1987). T. pyri has been recorded on nu- merous trees and bushes in Europe, Asia, North Africa, North America, Australia and New Zea- land (Chant & Yoshida-Shaul 1987). Typhlodromus laurae Arutunjan Fig. 15 Diagnosis: Idiosoma 363 pm. Dorsal shield reticulated and lightly sclerotized, with 4 pairs of 103ENTOMOL. FENNICA Voi. 4 • Tuovinen: Phytoseiid mites in apple plantations prominent pores, one of them anterior to setae Z4. Setae Z 5 with veryfaint serration. Ventrianal shield with 4 pairs of preanal setae (15 pm). Spermatheca narrow spur-shaped. Movable digit of chelicerae has 2 teeth. Macrosetae on basitarsus (50 pm), and shorter macrosetae on tibiaof leg IV. Distribution and host plants: Only one fe- male found in Piikkiö (60°23'N, 22°33'E) on Ribes nigrum. T. laurae has been recorded on Pinus sp. in Armenia (ref. Chant & Yoshida- Shaul 1987), and in Norway (Karg & Edland 1987), the Netherlands and Germany (Chant & Yoshida-Shaul 1987). Typhlodromus andrei Karg Fig. 16 Typhlodromus pritchardi Arutunjan (suspected synonym, Chant & Yoshida-Shaul 1987). Diagnosis: Idiosoma 376 pm. Dorsal shield lightly reticulated, with 4 pairs of distinct solenostomes plus smaller pores anteriorly and posteriorly to setae J2. Ventrianal shield with 4 pairs of preanal setae (15 pm) and one pair of pores. Spermatheca cup-shaped, with sharp an- gular bottom. Movable digit of chelicerae has 2 teeth. Macrosetae (52 pm) on basitarsus of leg IV. T. andrei and T. pritchardi Arutunjan are considered as possible synonyms (Chant & Yoshida-Shaul 1987), and this conception is adopted here. Distribution and host plants; Found only in Elimäki (60°44'N, 26°24'E) on Pterocarya rhoi- folia. T. andrei has been recorded on bark of fruit trees in Belgium (Karg 1982), T. pritchardi on Fragaria sp., Pinus sp., Primula vulgaris and Prunus spinosa in Armenia and Yaroslavl, Rus- sia (Moraes et al. 1986). GenusPhytoseiulus Evans Phytoseiulus persimilis Athias-Henriot Fig. 17 Phytoseiulus riegeli Dosse, Chant; Amblyseius tardi Lom- bardini, Kennett & Caltagirone. Diagnosis: Idiosoma 340 pm, orange col- oured. Dorsal shield smooth, without reticula- tion, weakly sclerotized, with 7 pairs of small but distinct pores. Setae are serrated except jl, z2, z5, S 5 and J5. Ventrianal shield small, with no preanal setae. Spermatheca narrow, with a stricture. Movable digit of chelicerae has 1 tooth. Macro- setae (116 pm) on basitarsus on leg IV. Distribution and host plants: One specimen found in Paimio (60°25'N, 22°42'E) on Malus domestica, obviously originating from a glass- house. P. persimilis is used in glasshouses for the control of spider mites. It has been recorded on various trees, bushes and herbaceous plants in Mediterranean countries and South America (Moraes et al. 1986). The species has been intro- duced and is established in many countries. It probably cannot survive the Finnish climate, be- cause of its temperature requirements (Kennett & Caltagirone, 1968). GenusProprioseiopsis Munia Proprioseiopsis okanagensis (Chant) Fig. 18 Typhlodromus ( Amblyseius) okanagensis Chant; Typhlo- dromus okanagensis levis Wainstein, Karg. Diagnosis: Idiosoma 401 pm (392-412). Dorsal shield smooth, withoutreticulation, weakly sclerotized, with 9 pairs of pores. Ventrianal shield reticulate, lightly sculptured, with 3 pairs of preanal setae and I pair of small, distinct pores. Spermatheca narrow bell-shaped, distinctly scleroticed. Movable digit of chelicerae has 1 tooth. Macrosetae on basitarsus (61-64 pm), genu and tibia of leg IV. Distribution and host plants: Found in Juva (61°53'N, 26°5rE) on cultivated strawberry Fragaria X ananassa and in Åland (60°15'N, 19°58'E) on Ribes nigrum. P. okanagensis has been recorded on fruit trees, herbaceous plants and in litter and soil in North America and Eu- rope (Moraes et al. 1986). 104 Tuovinen: Phytoseiid mites in apple plantations • ENTOMOL. FENNICA Vol. 4 GenusEuseius Wainstein Euseius finlandicus (Ondemans) Fig. 19 Seiulusfinlandicus Oudemans; Typhlodromus (Amblyseius) finlandicus (Oudemans), Chant. Diagnosis: Idiosoma 328 pm (304-344). Dorsal shield pale, weakly sclerotized, faintly reticulated, with 4-6 pairs of pores. Ventrianal shield with 1 pair of distinct, crescentic pores and 3 pairs ofpreanal setae in anterior part of the shield. Spermatheca narrow, with a stricture in neck. Movable digit of chelicerae has 1 or 2 teeth. Macrosetae on basitarsus (53 pm, 44—62) and shorter macrosetae on tibia and genu of leg IV. Distribution and host plants: Common on deciduous trees and bushes; found on Acer platanoides, Aesculus hippocastani, Alnus incana, Amelanchier spicata, Aristolochia macrophylla, Betula lutea, Cornus alba, Corylus avellana, Crataegus coccinea, Fagus grandifolia,Fragaria vesca, Fraxinus excelsior, Juglans ailanthifolia, J. cinerea, J. mandshurica, Malus sp., Prunus avium, P. padus, Pterycaria rhoifolia, Pyrus communis, Quercus robur, Ribes nigrum, R. ruhrum, R. uva-crispa, Rubus fruticosus, R. odoratus, Salix sp., S. caprea, Sorbus thuringiana, Tiliä americana, T. cordata. Tiliä x euchlora, Ulmus glabra. Viburnum opulus. E. finlandicus is the most widespread and abundant species in Finland. It has been recorded on numerous trees and bushes, less frequently on herbaceous plants, in all parts of the world. Only one report of the total of 123 references listed by Moraes et al. (1986) states that the species was found in litter, and there are no observations of the species in soil. Genus Amblyseius Berlese Key to species 1. Great differences in lengths of dorsal setae, j 3 at least three times longer than j4, j 5 and z 5 2 j4, j 5 and z 5 normal, not much shorter than j 3 3 2. Z 4 (89 (im, 76-96) longer than Z 5 (68 (im, 60-80), dorsal shield heavily sclcrolized and reticulated, often brown coloured; spermatheca long, narrow v-shaped; ventrianal shield with one pair of pores subsolidus Z 5 (71 nm, 68-72) longer than Z 4 (52 |xm, 50-53); dorsum not brown; spermatheca dish-shaped, strongly sclerotized with a prominent atrium; no pores on ventrianal shield tenuis 3. J 2 and Zl shorter than S 2; spermatheca bell-shaped .4 J 2 and Zl about equal to S2; spermatheca not bell- shaped 5 4. Ventrianal shield with onepair ofdistinct ‘eye-shaped’ pores; ratio of Z 4 (44 pm, 34-48): S 4 (28 pm, 19-32) = 1.5-1.6; length of idiosoma under 360 pm reductus Ventrianal shield with one pair of normal circular pores; length of Z 4 (38 pm) about equal to S 4 (33 pm); length of idiosoma over 360 pm cucumeris 5. Dorsal shield reticulated; spermatheca a wide v-shaped funnel with a neck zwoelferi Dorsal shield without reticulation; spermathecanarrow, long tube-shaped barken Amblyseius subsolidus (Beglyarov) Fig. 20 Typhlodromus subsolidus Beglyarov; Neoseiulus (Ambly- seius) canadensis (Chant & Hansell), Wainstein; Neoseiulus subsolidus (Beglyarov), according to Moraes et al. (1986); Typhlodromips subsolidus (Beglyarov), according to Karg (1991). Diagnosis: Idiosoma 389 pm (356-440). Dorsal shield heavily sclerotized and markedly reticulate, often brown-coloured, with 3-6 pairs of obscure pores. Setae Z 5 serrated. Ventrianal shield large, convex, about as long as wide, reticulate, with 1 pair of pores and 3 pairs of preanal setae. Spermatheca long, V- shaped. Movable digit of chelicerae has 2 prominent teeth. 3 short, barely differentiated macrosetae on basitarsus of leg IV, the longest one 27 pm (20-30). Dutch specimens of A. subsolidus have longer setae than Canadian specimens (Miedema 1987)and the same is also true ofFinnish specimens. Distribution and host plants; Found on Crataegus coccinea, Malus sp., Prunuspadus. A. subsolidus has been recorded on trees and bushes in Leningrad and Yaroslavl regions in Russia, in Alaska and in Canada (Moraes et al. 1986). 105ENTOMOL. FENNICA Voi. 4 • Tuovinen: Phytoseiid mites in appleplantations Amhlyseius tenuis (Hirschmann) Fig. 21 Typhlodromus tenuis Hirschmann; Typhlodromips (Typhlodromus) tenuis (Hirschmann), according to Moraes et al. (1986). Diagnosis: Idiosoma 357 pm (356-360). Dorsal shield smooth, with 4-5 pairs of obscure pores plus 1 pair of prominent pores anterior to setae S5. Setae Z 5 and Z 4 very faintly serrated. Ventrianal shield with 3 pairs of preanal setae. Spermatheca heavily sclerotized, with a distinct atrium. Movable digit of chelicerae has 2 teeth. Macrosetae (74 pm, 73-76) on basitarsus of leg IV. Shorter macrosetae on genu and tibia. Distribution and host plants: Found inFinland only in Juva (61°53'N, 26°51'E) on Fragaria x ananassa. Earlier records of A. tenuis are on ‘burnt wood’ in Germany and on Ruhus sp. in Canada (Moraes et al. 1986) and, according to Karg (1991), in litter in central Europe. Amhlyseius reductus Wainstein Fig. 22 Neoseiulus (Amhlyseius ) reductus (Wainstein), according to Moraes et al. (1986). Diagnosis: Idiosoma 336 pm (328-344). Dorsal shield lightly reticulated and sclerotized, with 3-5 pairs of distinct pores on dorsal shield. Setae Z 5 slightly serrated. Ventrianal shield pentagonal, lightly reticulated, with 1 pair of slender ‘eye-shaped’ pores and 3 pairs ofpreanal setae. Spermatheca bell-shaped, twice as long as broad. Movable digit of chelicerae with 1 tooth. Macrosetae (45 pm, 40-56) on basitarsus of leg IV. Distribution and host plants: Found inFinland on Aristolochia macrophylla, Fragaria vesca, Fragaria x ananassa, Malus sp., Rihes rubrum, Ruhus idaeus, Tussilago farfara, and Ulmus glabra. A. reductus has been recorded on various trees, bushes and herbaceous plants in Eurasia (Moraes et al. 1986). It has been used in the biological control of mites on strawberry in Russia (Tokunova & Malov 1988). Amhlyseius cucumeris (Oudemans) Fig. 23 Typhlodromus cucumeris Oudemans; Neoseiulus (Typhlodromus) thripsi (MacGill), Evans; Amhlyseius coprophilus Karg, Karg; Neoseiulus (Typhlodromus ) cucumeris (Oudemans), according to Moraes et al. (1986). Diagnosis: Idiosoma 375 pm (370-380). Dorsal shield lightly reticulated, with 5 pairs of distinct pores. Setae Z 5 faintly serrated. Ventri- anal shield with 3 pairs of preanal setae and 1 pair of pores. Spermatheca narrow bell-shaped. Movable digit of chelicerae has 1 tooth. Macro- setae (48 pm) on basitarsus on leg IV. Distribution and host plants: Found outdoors only in Piikkiö (60°23'N, 22°33'E) on Fragaria x ananassa (originating from earlier artificially introduced specimens). A. cucumeris is used in biological control of the onion thrips Thrips tabaci Lind. Ithas been recorded on various trees, bushes and herbaceous plants, e.g. on strawberries in Europe, North America and New Zealand (Moraes et al. 1986). Karg (1991) lists Phyto- nemuspallidus ssp .fragariae (Zimm.) among its prey species. Amhlyseius zwoelferi (Dosse) Fig. 24 Typhlodromus zwölferi Dosse, 1957;Neoseiulus zeitunicus Wainstein & Arutunjan, Wainstein; Neoseiulus (Typhlodromus) zwölferi (Dosse), according to Moraes et al. (1986). Diagnosis: Idiosoma 418 pm (408-440). Dorsal shield distinctly reticulated, often with pigmented areas present, and with 7 pairs of small pores. Setae Z 5 slightly serrated. Ventrianal shield reticulated, with 3 pairs of preanal setae and 0-1 pair of small pores. Spermatheca wide funnel-shaped without neck. Movable digit of chelicerae without teeth. Macrosetae on basitarsus (51 pm, 48-54), another much shorter macroseta on tibiaof leg IV. Distribution and host plants; Found in Åland (60° 15'N, 19°58'E) on Rihes nigrum and Fragaria xananassa and in Mikkeli (61 °4O'N, 27°12'E) on 106 Tuovinen: Phytoseiid mites in apple plantations • ENTOMOL. FENNICA Vol. 4 Fragaria x ananassa. A. zwoelferi has been re- corded earlier mainly on herbaceous plants and fruit trees in Europe and North America (Moraes etal. 1986). Amblyseius barken (Hughes) Fig. 25 Neoseiulus harkeri Hughes; Amblyseius mckenziei Schuster & Pritchard, Ragusa & Athias-Henriot. Diagnosis: Idiosoma 384 p,m (372-406). Dorsal shield slightly reticulated, with 4 pairs of distinct pores. Setae Z 5 faintly serrated. Ventri- anal shield indistinctly striated, with 1 pair of distinct pores and 3 pairs of preanal setae. Sper- matheca tube-shaped, atrium heavily sclerotized. Movable digit of chelicerae has 1 tooth. Macro- setae (70 pm, 66-74) on basitarsus of leg IV. Distribution and host plants: Only in glass- houses where A. barkeri is used for the biologi- cal control of thrips. A. barkeri has been re- corded on various trees, bushes and herbaceous plants in Europe and Asia (Moraes et al. 1986). Acknowledgements. For the identification and confir- mation of many specimens of Phytoseiidae, I want to thank Mrs. Eiko Shaul and Dr. D. A. Chant (University of Toronto, Canada). I am much indebted to Dr. T. Edland (Norwegian Plant Protection Institute, Norway), who pro- vided me with specimens of Phytoseiidae collected in Norway. I want to express my gratitude to Prof. D. Kropczynska, who has guided me in the working methods and systematics of Phytoseiidae. References Athias-Henriot, C. 1960: Nouveaux Amblyseius d’Algerie (Parasitiformes, Phytoseiidae). Acarologia 2:288- 299. Beglyarov, G. A. (Benibiapon, T. A.) 1981: Keys to the determination of phytoseiid mites of the U.S.S.R. (In Russian) Information Bulletin lOBC EPS. No 2, Vol. 1 and 2. 95 and 47 pp. Chant, D. A. 1957: Descriptions of some phytoseiid mites (Acarina: Phytoseiidae). Part I: Nine new species from British Columbia with keys to the species of British Columbia. Part 11. Redescriptions of eight species de- scribed by Berlese. Can. Entomol, 89:289-308. 1959: Phytoseiid Mites (Acarina: Phytoseiidae. Part I: Bionomics of seven species in Southeastern England. Part 1I:A taxonomic review of the family Phytoseiidae, with descriptions of 38 new species. Can. Entomol. 41, Suppl. 12. 164pp. 1965: The identity and distribution of species of Phytoseius Ribaga in Canada. Can. Entomol. 97:897-909. 1985:The Phytoseiidae. External anatomy. In: Helle, W. & Sabelis, M. W. (eds.). Spidermites. Their biology, natural enemies and control. World Crop Pests IB;5- 16. Chant, D. A. & Hansell, R. I. C. 1971: The genus Amblyseius (Acarina; Phytoseiidae) in Canada and Alaska. Can. J. Zool. 49:703-758. Chant, D. A. & Yoshida-Shaul, E. 1982: A world review of the soleiger species group in the genus Typhlo- dromus Scheuten (Acarina: Phytoseiidae). Can. J, Zool. 60:3021-3032. 1986; The subfamily Chantiinae in the family Phyto- seiidae (Acari: Gamasina). Can. J. Zool, 64:2024- 2034. 1987: A world review of the pyri species group in the genus Typhlodromus Scheuten (Acari: Phytoseiidae). Can. J. Zool. 65:1770-1804. 1989: Adult dorsal setal patterns in the family Phyto- seiidae (Acari: Gamasina). Int. J. Acarol. 15:219- 233. Denmark, H. A. & Rather, A. O. 1984: Revision of the genus Typhloctonus Muma, 1961 (Acarina: Meso- stigmata). Int. J. Acarol. 10:163-177. Dosse, G, 1956: Über die Entwicklung einiger Raubmilben bei verschiedenen Nahrungstieren (Acar,, Phytoseii- dae). Pflanzenschutzberichte 16:122-136. 1958: Die Spermathecae, ein zusätzliches Bestim- mungsmerkmal bei Raubmilben. (Acar., Phytoseiidae). Pflanzenschutz-Berichte 21:44-61. Edland, T. 1987: Rovmiddar (Phytoseiidae) på frilands- vekstar i Norge. [Predacious mites (Phytoseiidae) on field-grown plants in Norway.] Entomol. Tidskr. 108:21-22. Evans, G. O. 1987: Mesostigmata. Observations on the descriptive morphology and classification of the Phytoseiidae. In: Evans, G. O. & Murphy, P. W. (eds.). The Acari, A practical manual. I. Morphology, systematics of the subclass and classification of the mesostigmata: 153-166. University of Nottingham, School of Agriculture. Sutton Bonington, Leics. Hansen, E. W. & Johnsen, S. 1986: Rovmider av familien Phytoseiidae i Danmark (Acarina, Gamasina). [Preda- cious mites in the family Phytoseiidae in Denmark (Acarina, Gamasina.] Entomol. Meddelel. 53:137- 142. (In Danish) Helle, W. & Sabelis, M. W. (eds.) 1985: Spider mites. Their biology, natural enemies and control. World crop pests 18. Elsevier 8.V., Amsterdam. 458 pp. Karg, W. 1970: Neue arten der Raubmilbenfamilie Phyto- seiidae Berlese 1916. Deutsche Entomol. Zeitschr. 17:289-301. 1971: Die freilebenden Gamasina (Gamasides), Raubmilben. In: Die Tierwelt Deutschlands und 107ENTOMOL. FENNICA Voi. 4 • Tuovinen: Phytoseiid mites in apple plantations der angrenzenden Meeresteile nach ihren Merkmalen und nach ihre Lebensweise. 59. VEB Gustav Fischer Verlag, Jena. 475 pp. 1982: Diagnostik und Systematik der Raubrailben aus der Familie Phytoseiidae Berlese in Obstanlagen. Zool. Jahrb. Syst. 109:188-210. 1983: Systematische Untersuchung der Gattungen der Raubmilbenfamilie Phytoseiidae Berlese 1916mit der Beschreibung von 8 neuen Arten. Mitt. Zool. Mus. Berlin 59:293-328. 1991: Die Raubmilbenarten de Phytoseiidae Berlese (Acarina) Mitteleuropas sowie angrenzender Gebiete. Zool. Jahrb. Syst. 118:1-64. Karg, W. & Edland, T. 1987: Neue Raubmilbenarten der Phytoseiidae Berlese, 1916. Deutsche Entomol. Zeitschr., N. F. 34:387-395. Kennett, C. E. & Caltagirone, L. E. 1968: Biosystematics of Phytoseiulus persimilis Athias-Henriot (Acarina: Phytoseiidae). Acarologia 10:563-577. Kolodochka, L. A. (KojioitouxKa, Jl. A.) 1980:New spe- cies of phytoseiid mites from the fauna of USSR (Parasitiformes: Phytoseiidae). (In Russian). Vestnik Zool. 2:64-70. Kropczynska, D. & Tuovinen, T. 1987: Predatory mites (Acari: Phytoseiidae) occurring on apple-trees in Fin- land. Entomol. Tidskr. 108:31-32. 1988; Occurrence of predatory mites (Acari: Phyto- seiidae) on apple trees in Finland. Ann. Agric. Fennicae 27:305-314. Listo, J., Listo, E.-M. & Kanervo, V. 1939: Studies of the fruit tree red mite (Paratetranychus pilosus C, & F.). (In Finnish, English summary) Valt. Maatalouskoet. Julk. 99:1-143. Miedema, E. 1987: Survey of phytoseiid mites (Acari: Phytoseiidae) in orchards and surrounding vegetation of northwestern Europe, especially the Netherlands. Keys, descriptions and figures. Neth. J. Plant Pathol. 93, Suppl. 2:1-64. Moraes, G. 1.,McMurtry, J, A. & Denmark, H. A. 1986:A catalog of the mite family Phytoseiidae. References to taxonomy, synonymy, distribution and habitat. Empresa Brasileira de Pesquisa Agropecuaria. Depar- tamento Difusao de tecnologia, Brasilia DF. 353 pp. Oudemans, A. C. 1915: Acarologische Aanteekeningen LVI. Entomol. Berichten 4:180-188. Rowell, H. J., Chant, D. A. & Hansell, R. I. C. 1978: The determination of setal homologies and setal patterns on the dorsal shield in the family Phytoseiidae. Can. Entomol. 110:859-876. Tokunova, M. V. & Malov, N. A. (ToKynona, M. B. & Majion, H. A.) 1988:Biological methods of pest con- trol in strawberry. (In Russian) Zaschita Rastenij 5:37-38. Received 5.11. 1992 Fig. 3-25. Species of Phytoseiidae. Females: spermatheca, ventrianal area, dorsal shield (scale bar for dorsal shield, 100 pm). 108 Tuovinen: Phytoseiid mites in apple plantations • ENTOMOL. FENNICA Vol. 4 II Experimental & Applied Acarology, 12 (1991) 35-46 Elsevier Science Publishers 8.V., Amsterdam 35 Phytoseiid mites (Acari: Phytoseiidae) on apple trees and in surrounding vegetation in southern Finland. Densities and species composition T. Tuovinen 3 and J.A.H. Rokx b 'lnstitute ofPlant Protection, Agricultural Research Centre, SF-31600 Jokioinen, Finland bDepartment ofEntomology, Agricultural University. Wageningen, Netherlands (Accepted 18 January 1991) ABSTRACT Tuovinen, T. and Rokx, J.A.H., 1991. Phytoseiid mites (Acari: Phytoseiidae) on apple trees and in surrounding vegetation in southern Finland. Densities and composition ofspecies. Exp. Appi Acarol. , 12: 35-46. Leaf samples were collected from sprayed (n 29) and unsprayed (n= 19) apple orchards, from the surrounding vegetation (n = 58) and from one arboretum (n = 12), altogether from 46 plant spe- cies (1-5 samples each). The densityofphytoseiid mites averaged 1.2 mites/leafon unsprayed apple trees, but only 0.06 mites/leaf on sprayed trees. The phytoseiid density exceeded 1/leafon Aesculus hippocastani, Aristolochia macrophylla, Corylus avellana, Fragaria vesca, Fraxinus excelsior, Juglans cinerea, Pterocarya rhoifolia, Ribes nigrum, Rubus odoratus, Sorbus aucuparia, S. thuringiaca, Tiliaxeuchlora and Ulmus glabra. Other common trees and bushes inhabited by phytoseiids were Crataeguscoccinea (0.2 mites/leaf), Prunuspadus (0.7), Salixcaprea (0.4), and Tiliacordata (0.9). Twelve species of phytoseiid mites were found, of which ten occurred on unsprayed apple trees. The most widely distributed species on apple trees were Phytoseius macropilis (in 79% ofunsprayed samples), Euseius finlandicus (74%), Paraseiulus soleiger (53%), Paraseiulus triporus (37%), Am- blyseius canadensis (26%) andAnthoseius rhenanus (26%). The highest densities onapple trees were found in populations ofE. finlandicus (mean 0.7 mites/leaf), Ph. macropilis (0.5) and A. canadensis (0.5). On sprayed apple trees, E. finlandicus, Pa. soleiger and Ph. macropilis occurred most com- monly, but their mean densities were under 0.1 /leaf. Almost no phytoseiids were found in orchards sprayed with oxydemetonmethylbefore blooming of apple. On other plants, E. finlandicus occurred most commonly (on 33 plant species) and in the highest densities, followed by Ph. macropilis (14), Pa. soleiger (12), Pa. triporus (12) and An. rhenanus (7). Seiulus aceri and Paraseiulus talbii were identified as new phytoseiid species in Finland. It is con- cluded that deciduous trees and bushes in forest margins around orchards can serve as important reservoirs for phytoseiid mites, and that the dominant species in these plants would migrate into and colonize the orchards if the use ofharmful chemicals were restricted. INTRODUCTION Phytoseiid mites (Acari: Phytoseiidae) are important predators of the Eu- ropean red spider mite Panonychus ulmi (Koch) (Acari: Tetranychidae) on 0168-8162/91/$03.50 © 1991 Elsevier Science Publishers B.V. All rights reserved. 36 T. TUOVINEN AND J.A.H. ROKX unsprayed apple trees in Finland (Kropczynska and Tuovinen, 1987, 1988). Surveys conducted in apple orchards in many countries have demonstrated that phytoseiids can keep spider mite densities below economic thresholds ( Dosse, 1960; Collyer, 1964;Wildbolz, 1986). The use ofphytoseiids to con- trol spider mites in orchards is also well documented (Croft and Bames, 1971; McMurtry and van de Vrie, 1973; Hoy, 1982). In many cases, the introduced phytoseiid mites are conserved by using selective pesticides. In Europe, the predatory mite species most commonly used in integrated pest management (IPM) programs is Typhlodromus pyri (Scheuten). This species occurs generally and has strains resistant to organophosphorous insec- ticides (OPs; Hoyt, 1972; Overmeer and vanZon, 1983). Typhlodromus pyri is capable ofmaintaining spider mite populations under economic thresholds in commercial orchards (Wildbolz, 1986). Typhlodromus pyri has not been found in Finland, but other phytoseiids have been detected on sprayed apple trees in very low numbers (Kropczynska and Tuovinen, 1988). In the Nordic countries, phytoseiid mites occur on many deciduous trees and bushes (Hansen and Johnsen, 1986; Edland, 1987). These plants may serve as reservoirs for phytoseiid mites, allowing them to migrate into the orchard if harmful pesticides are not used. In Switzerland, Boiler et al. (1988) studied mite samples from hedges and forests near vineyards and found T. pyri on some of the trees and bushes. They concluded that hedges are impor- tant reservoirs of T. pyri in areas where pesticides are regularly applied. Our preliminary observations of phytoseiids on different plants showed that the plant itself may have characteristics affecting phytoseiid mite populations. Therefore we conducted a more thorough study of the phytoseiids on various species of trees and bushes. The trees most often used in windbreak hedges in Finland are alders (Alnus spp.) and spruce ( Picea abies), although the natural vegetation usually sup- plies enough protection from strong wind. Common deciduous trees are birches (Betula pendula and B. pubescens), alders (Alnus glutinosa and A. incana ), great sallow (Salix caprea), mountain ash (Sorbus aucuparia), bird cherry ( Prunuspadus) and aspen (Populus tremula). Bushes such as willow {Salix sp.), hawthorn {Crataeguscoccinea), raspberry {Rubusidaeus), hazel {Corylus avellana) and elder {Sambucus racemosa) are also common near orchards. As well as the above, there are often various planted trees and bushes of foreign origin. This study presents the results of a survey on the phytoseiid mites occurring in apple orchards and on nearby plants. The aim of the study was to evaluate the importance of surrounding vegetation as a reservoir and possible source of phytoseiid mites, especially the species that occur frequently on apple trees, and to establish if the phytoseiid mite species on apple tree show any resis- tance to commonly applied insecticides. PHYTOSEIIDS ON APPLE TREES AND IN SURROUNDING VEGETATION IN FINLAND 37 MATERIALS AND METHODS Most of the leaf samples were collected from commercial orchards and their surroundings in southern Finland and on the Åland Islands in August and September, 1989. The standard sample size was 100 leaves, with the excep- tion of some broadleaf samples, which consisted of 10-50 leaves (Table 1). For each sample, the leaves were taken from 10-20 sprayed apple trees in commercial orchards, from single or a few unsprayed trees in home gardens, and from several specimens of various deciduous trees or bushes near the orchards. A special survey was made in the Mustila arboretum (Elimäki, 60°44'N, 26°24'E), where many unusual plant species are grown. The num- ber of samples other than those of apple was restricted to a maximum of five. In order to find the most suitable host plants for phytoseiid mites, samples were taken from a range of plant species. The samples were either stored for a few days at +6-B°C or they were handled immediately. First, a subsample of 5-10 leaves was examined under a stereomicroscope to check for the presence of eriophyid mites (Acari: Er- iophyidae), an important food of many phytoseiid species. The leaves were then soaked in warm soapy water (+ 70°C, 0.5% Taski profi soap) to remove and kill the mites on the leaves. After 24 h the samples were passed through 1-mm and 0.1 mm-mesh sieves. The phytoseiid mites were counted and col- lected into small tubes, and stored in 70% alcohol until preparation and iden- tification. The mites were identified using the keys ofKarg (1971,1982, 1983) and Miedema (1987), the reference collection provided by T. Edland (1988, The Norwegian Plant Protection Institute), and the collection of Kropczyn- ska and Tuovinen (1988). RESULTS The occurrence of phytoseiid mites and the presence of a common food source for phytoseiids, eriophyid mites, on apple trees and 46 other plants are presented in Table 1. The highest phytoseiid densities were found in single samples on horse chestnut (Aesculus hippocastani; max. 14.4/leaf), blackcurrant ( Ribes ni- grum; 4.7), ash (Fraxinus excelsior, 3.8), mountain ash (3.3), hazel (3.3), Dutchman’s pipe (Aristolochia macrophylla; 3.0), apple, unsprayed, cv. Har- lamowska (2.8), purple raspberry (Rubus odoratus; 2.7), forest strawberry (Fragaria vesca; 2.4), lime ( Tiliaxeuchlora ; 2.3) and Pterocarya rhoifolia (2.3). Because the leaves of plants differ markedly in size, the values in Table 1 and above do not refer to the real density. In this survey, twelve phytoseiid species were identified, ten on unsprayed apple trees, six on sprayed apple trees and eleven on various plants (Table 2). The most widely distributed phytoseiid species on unsprayed apple trees 38 T. TUOVINEN AND J.A.H. ROKX TABLE 1 Occurrence ofphytoseiid and eriophyid mites in samples* collected from apple orchards and nearby plants Plant species Samples (n) Phytoseiids/sample Eriophyidsb Deciduous trees Malusdomestica (sprayed) 29 5.5 + + + M. domestica (unsprayed) 19 116.8 + Acerplatanoides 3 21.0 Aesculus hippocastani (15) 2 118.5 Alnus glutinosa 2 1.0 + + A. incarta 1 2 + + Betula pendula 2 0.0 B.luteaUc 1 40 Fagus grandifoliaM 1 8 Fraxinus excelsior (50) 2 98.5 + + + Prunus padus 3 67.3 P. cerasus 2 3.5 P. avium 2 0.0 Pyrus communis 1 1 Salixcaprea 1 35 Sorbus aucuparia 2 170.5 + S. aucupariaxintermedia 1 0 5. thuringiaca 1 111 Tiliä americana M 1 27 T.cordata 2 88.0 T.euchloraM 1 228 Ulmus glabra 2 115.0 + Deciduous bushes AmelanchierspicataM 1 2 Aristolochia macrophyllaM (30) 1 89 Betula nana 1 0 + Cornusalba 1 77 Corylus avellana 5 167.6 + Crataegus coccinea 3 21.0 JuglansailanlhifoliaM(10) 1 9 - J.cinerea M (10) 1 15 7. mandschurica M (10) 1 6 Philadelphus sp. M 1 6 PterocaryarhoifoliaM (30) 1 68 - ft/fes nigrum 2 237.0 R.rubrum 2 11.0 /?. uva-crispa 1 4 ÄOM sp. 11 Rubusfruticosus 1 3 /?. i lOeriophyids/leaf. C M, samples from Mustila arboretum. TABLE 2 Occurrence” ofphytoseiid species on apple trees and the surrounding vegetation Phytoseiid Apple trees Found also on; species Sprayed Unsprayed (n = 29) (n= 19) Phytoseius macropilis (Banks) 4.2 46.1 17.2% 78.9% Euseius finlandicus (Oudemans) 8.0 73.2 41.4% 73.7% Amblyseius reductus Wainstein 1.0 2.3 3.4% 5.3% Amblyseius canadensis Chant & Hansel! 0 45.8 0% 26.3% Seiulus aceri (Collyer) 0 0 0% 0% Paraseiulus talbii (Athias-Henriot) 0 1.0 0% 5.3% Paraseiulus soleiger (Ribaga) 6.2 15.6 20.7% 52.6% Paraseiulus triporus (Chant & Shaul) 2.0 2.4 3.4% 36.8% Anthoseius bakeri (Carman) 0 0% 0 0% A. hippocastani, C. avellana, F. grandifolia, Fragaria Xananassa, P. avium, P. padus, R. fruticosus, R. rubrum, S. caprea, S. aucuparia, S. thuringiana, T. americana, U. glabra, V. opulus A. platanoides, A. hippocastani, A. incana, A. spicala, A. macrophylla, B. lutea, C. alba, C. avellana, C. coccinea, F. grandifolia, F. vesca, F. excelsior, J. ailanthifolia, J. cinerea, J. mandshurica, P. avium, P. padus, P. rhoifotia, P. communis, R. nigrum, R. rubrum, R. uva-crispa, R. fruticosus. R. odoratus, Salix sp., S. caprea, S. thuringiana, T. americana, T. cordata, Tiliaxeuchlora. U. glabra, V. opulus A. macrophylla, F. vesca, T. farfara, U. glabra C. coccinea, P. padus A. platanoides Fragaria X ananassa, J. ailanthifolia B. lutea, C. avellana, C. coccinea. F. grandifolia. F. excelsior, J. cinerea, J. mandshurica, P. rhoifotia, S. thuringiaca, T. cordata, Tiliaxeuchlora, V. glabra A. platanoides, A. hippocastani, C. avellana, F. vesca, P. avium, P. padus, P. rhoifotia, R. rubrum, R. uva-crispa, S. aucuparia, R. odoratus, U. glabra R. rubrum 3 39PHYTOSEIIDS ON APPLE TREES AND IN SURROUNDING VEGETATION IN FINLAND Phytoseiid Apple trees Found also on: species Sprayed Unsprayed (n =29) (n= 19) Anthoseius rhenanus (Oudemans) 2.0 5.8 A. glutinosa, C. coccinea, J. ailanthifolia, P. avium, R. nigrum, R. idaeus, S. aucuparia3.4% 26.3% Anthoseius gilvus (Wainstein) 0 1.0 n.a. 0% 5.3% Typhlodromusrichteri Karg 0 1.5 A. platanoides, S. aucuparia 0% 10.5% 'Mean numbers of miles and percentages of samples containing the species. were Phytoseius macropilis (Banks), Euseius fmlandicus (Oudemans), Para- seiulus soleiger (Ribaga), Paraseiulus triporus (Chant & Shaul), Amblyseius canadensis Chant & Hansell and Anthoseius rhenanus (Oudemans); E. fin- landicus, Ph. macropilis, A. canadensis and Pa. soleiger occurred in the high- est densities. Other species occurred in only a few samples and in very low densities. Fig. 1, The composition ofphytoseiid species on unsprayed and sprayed apple trees compared with twelve deciduous trees and bushes. Sampling in August-September 1989. 40 T. TUOVINEN AND J.A.H. ROKX PHYTOSEIIDS ON APPLE TREESAND IN SURROUNDING VEGETATION IN FINLAND 41 TABLE 3 Sprayings performed in 1989,and mean numbers ofphytoseiids in sprayed apple orchards Location Pesticides and number ofapplications Phytoseiids/ sample Fungicide 3 Acaricideb Insecticide0 Pohja dith:B flub:l dime:l 22.7 Virkkala bite:s chin:l azin:l 12.0 Pälkäne dith:3 chin:l 9.5 Paimio dith:s chin:2, fens:l dime:l 2.5 Geta bite:6 chin:l, chlo:l azin:2 2.0 Bromarv bite: 1, dich: 1 chin:l, tolu:2 1.0 dith:9 Pohja bite:3, dith:s chin:l azin:3 1.0 Lohjansaari dith:s, trif:4 chin:l oxyd:l 1.0 Virkkala bite: 1, dith: 1 azin:l,oxyd:2 0.5 trif:2 Geta bite:2, dich:2, azin:2, dime:2, 0 dith:2,trif:l oxyd:l Geta bite:3, copp:l, chin:l azin:l,dime:2 0 dich:3, dith:2 Godby bite: 1, dich: 1 azin: 1, oxyd: 1 0 dith:6 Godby dith:6 chin:2 azin:l,oxyd:3 0 Lohjansaari dith:6, trif:2 chin: 1 oxyd: 1 0 Lohjansaari bite:3, dith:4 dico:l oxyd:l 0 Piikkiö bite:6 chin:l oxyd:l 0 “Fungicides: bitertanol; copperoxychlorid: dichlofluanid; dithianon; triforine. bAcaricides: chinomethionate; chlorbenzilate; dicofol; fenson; flubenzimine; toluene. °lnsecticides: azinphosmethyl; dimethoate; oxydemetonmethyl. The material collected for the 1985 survey was rechecked, and one correc- tion was made to the list of phytoseiids on the apple tree: Amblyseius cucu- meris (Oudemans) should be A. reductus Wainstein (Kropczynska and Tuovinen, 1988). Furthermore, one specimen of Paraseiulus triporus, earlier identified erroneously as Pa. soleiger, was identified from the same material (T. Edland, personal communication, 1988). Paraseiulus talbii (Athios-Henriot) was found as a new species on the ap- ple tree in Finland, and Seiulus aceri (Collyer) was recorded for the first time on the maple (Acerplatanoides). The phytoseiid species found on apple trees now include Phytoseius macropilis, Euseius finlandicus, Amblyseius reductus, A. canadensis, Paraseiulus talbii, Pa. soleiger, Pa. triporus, Anthoseius bakeri (Garman ),An. rhenanus, An. gilvus (Wainstein) and Typhlodromus richteri Karg. Euseius finlandicus occurred on 85% of the plant species containing phy- toseiids (on 33 of 46 plants). The other species with a wide host-plant selec- tion were Ph. macropilis (on 14 plants), Pa. soleiger (on 12 plants) and Pa. 42 T. TUOVINEN AND J.A.H. ROK.X triporus (on 12 plants; Table 2). These four species accounted for 94.7% of all individuals («= 2219) in unsprayed apple leaf samples; the same species, especially E. finlandicus and Ph. macropilis, were also dominant on many common or otherwise interesting plants near orchards (Fig. 1). The presence of eriophyid mites in leaf samples does not seem to affect the density of phytoseiids (Table 1). On the dwarf birch (Betula nana) and the nettle ( Urtica dioica), eriophyid populations existed, but not a single phyto- seiid mite was found. The nettles were growing near the sprayed apple trees, and had obviously been sprayed with the same chemicals. Eriophyids were rather common on Alnus spp., but only a few phytoseiids were found on these trees. Six phytoseiid species were found in low densities on sprayed apple trees (Table 2). Euseius finlandicus, Pa. soleiger and Ph. macropilis were the most common species in these orchards, where several fungicidal and a few insec- ticidal and acaricidal sprayings had been performed (Table 3). Phytoseiids were almost entirely absent from orchards where oxydemetonmethyl had been used. In two of the orchards, no insecticidal sprayings had been made in 1989, but in the previous year, dimethoate (Pälkäne) and oxydemetonmethyl plus dimethoate (Bromarv) had been used (Table 3). In the orchards where about 10-20 phytoseiid mites/sample were found, the trees had been sprayed with bitertanol or dithianon for scab control, with acaricides once and with azin- phosmethyl or dimethoate no more than once. DISCUSSION Although the role of phytoseiid mites as important predators of P. ulmi on apple trees had already been observed in the 1930 s in Finland (Listo et al., 1939), the first survey to search for and identify phytoseiids was not con- ducted until 1985 (Kropczynska and Tuovinen, 1987, 1988). The observa- tions made for the present study and that performed four years earlier showed that the main species compositions and the densities of phytoseiid mites are stable in a particular orchard as long as the trees have not been sprayed. Like- wise, in Canada, Amano and Chant (1990) noted that populations of E. fin- landicus and Ph. macropilis, the two dominant phytoseiid species in an aban- doned orchard, were stable in two consecutive years. The most common phytoseiid mite species on apple trees in Finland, E. finlandicus and Ph. macropilis, are known as predators of spider mites and eriophyid mites (Chant, 1959; Böhm, 1960; Karg, 1972). Both species also reproduce when fed only on pollen, and E. finlandicus reproduces also if fed only on spores and hyphae ofthe apple mildew Podosphaera leucotricha (Ell. & Ev.) (Kropczynska-Linkiewicz, 1973). These two species of phytoseiids are clearly the best adapted to the Finnish climate and to diverse habitats and food resources. 43PHYTOSEIIDS ON APPLE TREESAND IN SURROUNDING VEGETATION IN FINLAND As Finnish apple orchards are small, with homogeneous blocks typically under 2ha and very seldom over 10 ha, the significance of the surrounding vegetation as a reservoir and source of phytoseiid mites is more important than in larger uniform apple cultivations. If the harmful agents in chemical pest control are replaced with more benign pesticides, predators and parasi- toids will migrate from surrounding vegetation and colonization may suc- ceed. As phytoseiids do not walk long distances (van de Vrie, 1985), the main means of long-range dispersal is the wind. Hoy (1982) reported that the phy- toseiid mite Metaseiulus occidentalis (Nesbitt) dispersed from one spot throughout a 32-ha almond orchard in one year. Phytoseiids can disperse via air turbulence for at least 200 m, and probably much more than that (Hoy et al., 1985). The capacity of phytoseiids for long-distance airborne dispersal seems to be so high that they might colonize small orchards within a short period. The speed of phytoseiid migration from outside trees or bushes into an or- chard depends on many factors, such as distance, prevailing wind direction, frequency of high winds, air temperature and relative humidity (Johnson and Croft, 1979; Hoy et al., 1985). The above-mentioned studies support the idea that phytoseiids may colonize small apple orchards in a few months once harmful sprayings have been stopped. In Switzerland, a method for transferring phytoseiids from one vineyard to another has recently been introduced and implemented on a larger scale (Boiler and Remund, 1986). It would also be useful to study whether artifi- cial transfer from wild host plants would significantly accelerate the migra- tion of phytoseiids into apple orchards. Other generally occurring good host plants for phytoseiids besides the apple tree are blackcurrant, mountain ash, hazel, purple raspberry, bird cherry, lime ( Tiliä cordata) and elm ( Ulmusglabra) . These trees and bushes are hosts for many eriophyid mite species (Liro and Roivainen, 1951), although in this study eriophyid mites were rather scarce. Other mite groups were not consid- ered, but with the exception of the European red spider mite on sprayed apple trees, their densities were much lower (cf. Kropczynska and Tuovinen, 1988). Many studies report high densities of phytoseiid mites on hazel (Hansen and Johnsen, 1986; Edland, 1987; Boiler et al., 1988). Although not very common in Finland, this bush can be found near many apple orchards. An- other very good host plant for phytoseiids is blackberry (Boiler et al., 1988), but in the present study only a few mites were found on it. Rubus odoratus, in contrast, was abundantly inhabited by E. finlandicus. Only a few phytoseiids were found on common raspberry (R. idaeus), but the wild raspberries should be studied more thoroughly because they are very common in forest margins. Although samples of some plant species were taken in only a single or a few locations, the results show which plant species can support high numbers of 44 T. TUOVINEN AND JAM. ROK.X phytoseiids. The presence of hairs on a leaf surface seems to be an important prerequisite for high phytoseiid density (cf. Overmeer and van Zon, 1984). Prey density does not seem to have any significant effect on the presence and density cfE. finlandicus and Ph. macropilis. Although only the density of eriophyid mites was estimated, the general trend was for phytoseiids also to be found on plants where only very few or no prey mites were present, at least on leaves. Obviously, these species have alternative food sources: pollen, spores and plant fluids, and possibly also the mites inhabiting branches. Prunus padus, Sorbus aucuparia and Salix caprea are all common trees in forest margins and around orchards. Euseius finlandicus and Ph. macropilis were dominant on Pr. padus, where their densities were almost the same as on unsprayed apple trees. Salix caprea is an interesting tree, because it pro- vides nourishment for honey bees in early spring, before apple blooming time. It should therefore be conserved and even used in windbreak hedges. As So. aucuparia is the main host of the most important apple pest in Finland, the apple fruit moth (Argyresthia conjugella (Zell.)), this tree should not be grown near apple orchards. Phytoseius macropilis was the dominant species on both Sa. caprea and So. aucuparia. The prospects of finding strains resistant to OPs in any phytoseiid species do not look promising in the light of the present study, although 10-30 spec- imens of E. finlandicus and Pa. soleiger were found in some sprayed samples. However, the findings suggest that these populations may possess at least a low level of resistance to dimethoate and azinphosmethyl, and clearly show the destructive effect of pesticide spraying on predatory mites. Use of oxyde- metonmethyl, one of the common insecticides, should be restricted if natu- rally occurring phytoseiids are to be conserved. Because the species most widely known to have developed resistance to OPs, T. pyri, has not been found in Finland so far, the introduction and release of this species into Finnish orchards should be studied, as should the reasons why this species does not occur in Finland. ACKNOWLEDGEMENTS The authors thank Dr. Eiko Shaul for the identification of Amblyseius re- ductus and Paraseiulus talbii. REFERENCES Amano, H. and Chant, D.A., 1990. Species diversity and seasonal dynamics of Acari on aban- doned apple trees in southern Ontario, Canada. Exp. Appi. Acarol., 8: 71-96. Boiler, E.F. and Remund, U., 1986. Methoden der Raubmilben-Ansiedlung in Rebbergen der Ostschweiz. Schweiz. Z. Obst-Weinbau, 122: 287-291. Boiler, E.F., Remund, U. and Candolfi, M.P., 1988. Hedges as potential sources of Typhlodro- PHYTOSEIIDS ON APPLE TREES AND IN SURROUNDINGVEGETATION IN FINLAND 45 mus pyri , the most important predatory mite in vineyards of northern Switzerland. Ento- mophaga, 33; 249-255. Böhm, H., 1960. Untersuchungen über Spinnmilbenfeinde in Österreich. Pflanzenschutzbe- richte, 25: 23-46. Chant, D.A., 1959. Phytoseiid Mites (Acarina; Phytoseiidae). Part I: Bionomics ofseven spe- cies in Southeastern England. Part II: A taxonomic review of the family Phytoseiidae, with descriptions of 38 new species. Can. Entomol., 41, Suppl. 12., 164 pp. Collyer, E., 1964. A summary of experiments to demonstrate the role of Typhlodromus pyri Scheut. in the control of Panonychus ulmi (Koch) in England. In; Proc. First Int. Congo Acarology, Fort Collins, CO, 2-7 September 1963. Acarologia 6, Facs. Hors Série, pp. 363- 371. Croft, B.A. and Barnes, M.M., 1971. Comparative studies on four strains of Typhlodromus oc- cidentalis. 111. Evaluations ofreleases ofinsecticide resistant strains into an apple orchard ecosystem. J. Econ. Entomol., 64: 845-850. Dosse, G., 1960. Überder Einfluss der Raubmilbe Typhlodromus liliae Oud. auf die Obstbaum- spinnmilbe Metatetranychus ulmi Koch (Acari). Pflanzenschutzberichte, 24; 113-137. Edland, T., 1987. Rovmiddar (Phytoseiidae) på frilandsvekstar i Norge. [Predacious mites (Phytoseiidae) on field-grown plants in Norway.] Entomol. Tidskr., 108: 21-22. Hansen, E.W. and Johnsen, S., 1986. Rovmider av familien Phytoseiidae i Danmark (Acarina, Gamasina). [Predacious mites in the family Phytoseiidae in Denmark (Acarina, Gama- sina).] Entomol. Medd., 53: 137-142. Hoy, M., 1982. Aerial dispersion and field efficacy of a genetically improved strain of the spi- der-mitepredator Melaseiulus occidentalis. Entomol. Exp. Appi., 32; 205-212. Hoy, M., Groot, R. and van de Baan, H.E., 1985. Influence of aerial dispersal on persistence and spread of pesticide-resistant Melaseiulus occidentalis in California almond orchards. Entomol. Exp. Appi., 37: 17-31. Hoyt, S.C., 1972. Resistance to azinphosmethyl of Typhlodromuspyri (Acarina: Phytoseiidae) from New Zealand. N.Z. J. Sci., 15: 16-21. Johnson, D.T. and Croft, 8.A., 1979. Factors affecting the dispersal ofAmblyseius fallacis in an apple tree ecosystem. In: J. Rodriguez (Editor), Recent Advances in Acarology, Vol. I. Ac- ademic Press, New York, NY, pp. 477-483. Karg, W., 1971. Die freilebenden Gamasina (Gamasides), Raubmilben. Die Tierwelt Deutsch- lands und der angrenzenden Meeresteile, Teil 59. Gustav Fischer, Jena, 475 pp. Karg, W., 1972. Untersuchungen über die Korrelation zwischen dominierenden Raubmilben- arten und ihrer möglichen Beute in Apfelanlagen. Arch. Pflanzenschutz., 8: 29-52. Karg, W., 1982. Diagnostik und Systematik der Raubmilben aus derFamilie Phytoseiidae Berlese 1916 in Obstanlagen. Zool. Jahrb. Syst., 109: 188-210. Karg, W., 1983. Systematische Untersuchung der Gattungen der RaubmilbenfamiliePhytosei- idae Berlese 1916mit der Beschreibung von 8 neuen Arten. Mitt. Zool. Mus. Berlin, 59: 293- 328. Kropczynska-Linkiewicz, D., 1973. Studies on feeding of four species of phytoseiid mites (Acarina; Phytoseiidae). In: M. Daniel and B. Rosicky (Editors), Proc. 3rd Int. Congr. Acarology, Prague, 31 August-6 September 1971. Czechoslovak Academy of Sciences, Pra- gue, pp. 225-227. Kropczynska, D. and Tuovinen, T., 1987. Predatory mites (Acari: Phytoseiidae) occurring on apple-trees inFinland. Entomol. Tidskr., 108: 31-32. Kropczynska, D. and Tuovinen, T., 1988. Occurrence of phytoseiid mites (Acari; Phytosei- idae) on apple trees in Finland. Ann. Agric. Fenn., 27: 305-314. Liro, I.J. and Roivainen, H., 1951. Suomen eläimet (Animalia Fennica) 6. Äkämäpunkit (Er- iophyidae). [Fauna of Finland (Animalia Fennica) 6. Gall mites (Eriophyidae). ] Vanamo, Turku, Finland, 281 pp. 46 T. TUOVINEN AND J.A.H. ROKX Listo, J., Listo, E.-M. and Kanervo, V., 1939. Studies of the fruit tree red mite (Paratetranychus pilosusC. & F.). (Summary). Valt. Maatalouskoetoiminnan Julk., 99: 1-143. McMurtry, J.A. and van de Vrie, M., 1973. Predation by Amblyseiuspotentillae (Garman) on Panonychus ulmi (Koch) in simple ecosystems (Acarina: Phytoseiidae, Telranychidae). Hilgardia, 42: 17-34. Miedema, E., 1987. Survey of phytoseiid mites (Acari: Phytoseiidae) in orchards and sur- rounding vegetation ofnorthwestern Europe, especially the Netherlands. Keys, descriptions and figures. Neth. J. Plant Pathol., 93, Suppl. 2: 1-64. Overmeer, W.P.J. and van Zon, A.Q., 1983. Resistance to parathion in the predacious mite Typhlodromus pyri Scheuten (Acarina: Phytoseiidae). Meded. Fac. Landbouwwet. Rijks- univ. Gent, 43: 247-251. Overmeer, W.P.J. and van Zon, A.Q., 1984. The preference of Amblyseius potentillae (Gar- man) (Acarina: Phytoseiidae) for certain plant substrates. In; D. Griffithsand C. Bowman (Editors), Proc. 6th Int. Congr. Acarology, Edinburgh, September 1982, Vol. 1. Ellis Hor- wood, Chichester, pp. 591-596. Van de Vrie, M., 1985. Control of Telranychidae in crops. Greenhouse ornamentals. In: W. Helle and M.W. Sabelis (Editors), Their Biology, Natural Enemies, and Control Spider Mites. Vol. B. Elsevier, Amsterdam, pp. 273-283. Wildbolz, T., 1986. Raubmilben als Spinnmilbenfeinde im Obstbau. Schweiz. Z. Obst-Wein- bau, 120:433-435. 111Agriculture, Ecosystems and Environment (sul Elsevier Science Publishers 8.V., Amsterdam (submitted) Influence of Surrounding Trees and Bushes on the Phytoseiid Mite Fauna on Apple Orchard Trees in Finland T TUOVINEN Institute of Plant Protection, Agricultural Research Centre of Finland, FIN-31600 Jokioinen (Finland) ABSTRACT Tuovinen, T. Influence of surrounding trees and bushes on the phytoseiid mite fauna on apple orchard trees in Finland. Agric. Ecosystems Environ. Predacious phytoseiid mites were collected from apple orchard trees and from nearby deciduous trees and bushes in order to compare the species composition and densities on apple as well as around orchards in Southern Finland. The majority of the specimens belonged to Euseiusfinlandicus and Phyloseius macropilis, which are considered to be the most relevant for natural control of the European red spider mite, Panonychus ulmi, in Finland. Phytoseiids occurred only occasionally in insecticide-treated orchards bordered by just a few suitable host plants, whereas they were more abundant in other sprayed orchards that were surrounded by many suitable host plants. P. macropilis was the dominant phytoseiid species on unsprayed apple trees, but E. finlandicus was more common in sprayed orchards. Both species were common also on host plants where spider mites were scarce. In a 2-ha orchard that was surrounded by deciduous trees and bushes, the mean phytoseiid mite density was 0.3- 3.1/leaf 15 days after a dimethoate treatment. Phytoseiid mites were encountered in the vicinity on the following trees: bird cherry, Prunus padus (0.3 mites/leaf); hazel, Corylus avellana (9.8/leaf); honeysuckle, Lonicera xylosleum (2.7/leaf); lime. Tiliä spp. (2.4/leaf); oak, Quercus robur (1.2/leaf) and great sallow, Salix caprea (0.8/leaf). E. finlandicus was the dominant species, both on apple trees and on other host plants, with the exception of great sallow trees. Phytoseiiddensities on adjacent vegetation had a noticeable effect on phytoseiid densities and species composition on apple orchard trees. Tall trees, such as oak and lime, are probably more important than low bushes as natural sources of phytoseiids for aerial dispersal into orchards. The migration of E. finlandicus into orchards from surrounding vegetation is concluded to be faster than that of P. macropilis. 2 INTRODUCTION In integrated pest management on apple trees, predacious phytoseiid mites (Acari; Phytoseiidae) have a prominent role as natural enemies of the European red spider mite Panonychus ulmi (Koch) (Acari: Tetranychidae) and other phytophagous mites (Collyer, 1964; Wildbolz and Staub, 1986; Trapman, 1989). Phytoseiid strains resistant to organophosphorus insecticides have been utilized in many countries (Hoyt, 1972; Overmeer and van Zon, 1983; Genini and Baillod, 1987). Resistant strains of phytoseiid mites have not been reported in Finland. The most important species in Europe, Typhlodromus pyri Scheuten, in which resistant strains have been detected, is very rare in Finland. It has been recorded only in the southwestern Åland islands (Tuovinen, unpublished). The import- ation and release of resistant strains of T. pyri into Finnish orchards may not offer a long-term solution to the spider mite problem because T. pyri may not tolerate the low temperatures typical of the Finnish winter (c.f. MacPhee, 1963). Phytoseiid mites are common on unsprayed apple trees in Finland, and spider mites are rare or entirely absent from such trees (Kropczynska and Tuovinen, 1988). Many other deciduous trees and bushes maintain high phytoseiid populations, including the same species which dominate on apple trees (Tuovinen and Rokx, 1991). The surrounding vegetation is thereforeassumed to be a reservoir for phytoseiid mites from which they migrate onto apple trees and thus regulate the density of phytophagous mites. This assumption was evaluated in commercial, insecticide-treated orchards during 1989 and 1991. The objective was to clarify the possible effects of adjacent plants on the occurrence of phytoseiid mites on apple trees, as well as to outline some of the conditions that would facilitate natural control of the European red spider mite. MATERIALS AND METHODS In 1989, 14 insecticide-treated apple orchards in Southern Finland and on the Åland islands were studied (Table 1). At the end of the season (August-September), samples of 100 leaves were collected from 10-20 apple trees in the 14 sprayed orchards, from single or a few unsprayed apple trees, if available nearby, and from 5-10 specimens of the main species of deciduous trees and bushes in the vicinity. In 1989, phytoseiid mites, and in 1991 also spider mites and tydeid mites (Acari: Tydeidae) were collected and counted. The leaf samples were soaked in warm soap water to remove and kill the mites on the leaves. After 24 hours, the soapy water with leaves was passed through 1 mm and 0.1 mm mesh sieves. 3 The phytoseiid mites were counted, placed in small tubes, and stored in 70% alcohol until mounting in Hoyer solution. The phytoseiid mites were identified using the keys ofKarg (1991) and Miedema (1987), and thereference collections of T. Edland (personal communication, 1988) and Kropczynska and Tuovinen (1988). The number of phytoseiids/sample was subjected to regression analysis to test the effect of time elapsed from the last harmful spray (Table 1). Harmful insecticides included azinphosmethyl, dimethoate and oxydemetonmethyl, and less harmful acaricides and fungicides (chinomethionate, chlorbenzilate, dichlofluanid, dicofol, flubenzimine and triforine) (Karg et al., 1987, Boiler et al., 1989, Hassan et al., 1991). The relationship of phytoseiid density in surrounding vegetation to the density on sprayed apple trees was assessed using Spearman's correlation. The phytoseiid density in surrounding vegetation was calculated as the sum of phytoseiid mites found on non-orchard plants using a coefficient varying from 0.2 to 20 according to the estimated size of the bushes or trees compared to apple trees (Table 1). The unsprayed apple trees were not included in the calculation, because they were few in number and were situated near dwellings. The mean densities of phytoseiid mites on different plants were calculated, including some additional samples taken from similar environments in 1990-1991. In 1991, apple leaf samples were collected from northern, western and eastern parts of a 2-ha orchard, and from the main surrounding trees and bushes, respectively. The main surrounding trees and bushes nearby (10-20 m away) were: on the western side willow (Salix spp.) and a few bird cherry trees (Prunus padus L.); on the northern side tall oaks (Quercus robur L.), hazels (Corylus avellana L.) and honeysuckles (Lonicera xylosteum L,); and on the western side tall limes (Tiliä cordala Mill.) and hazels. On the southern side of the orchard, about 30 m away, there were newly planted young nursery trees and no big trees. The orchard had been sprayed with dimethoate (120 g a.i./100 1, 500 g a.i./ha) 15 days prior to sampling. From tall oak and lime trees, lower (< 2 m) and higher leaves (10-12 m) were sampled again in July 1992 to check the vertical distribution of phytoseiid mites. The leaf samples were weighed. The number of mites/tree was calculated by estimating the weight of fresh leaves of whole trees according to the size of the trees. RESULTS Nine phytoseiid species in seven genera were identified in this study. Seven of the species occurred on apple trees (Table 2). On adjacent plants, the mean densities of phytoseiids varied between 0-1063 mites/100 leaves (Table 3). The 14orchards studied in 1989 included orchards with 4 adjacent vegetation inhabited by high densities of phytoseiid mites and orchards with sparse phytoseiid communities on adjacent plants (Table 4). Phytoseiid mites were encountered in all unsprayed apple leaf samples. The orchards studied were divided into three groups: in Group 1 the adjacent vegetation was characterized by high phytoseiid numbers, with moderate to high phytoseiid numbers on sprayed apple trees; in Group 2 the adjacent vegetation was characterized by high phytoseiid numbers, but low phytoseiid numbers on sprayed apple trees; in Group 3 both the adjacent vegetation and sprayed apple trees contained low phytoseiid numbers (Table 4). There was no significant correlation between numbers of phytoseiids on sprayed apple trees and on adjacent vegetation (Spearman r=0.348, N=l4, P=0.12). When one orchard (no. 10), with a high density of phytoseiids on a horse chestnut tree (Aesculus hippocastanum L.) in the vicinity and no phytoseiids on sprayed apple trees, was excluded from the analysis, the correlation was significant (r=0.585, N=l3, P=0.02). The interval between sampling date and the last insecticide spray rated as harmful to phytoseiids varied between 28 and 123 days (Table 1). The regression relationship between days elapsed from last insecticide treatment and density of phytoseiids on sprayed apple trees was not significant (r=0.437, P=0.12); neither was that of acaricide/fungicide treatment (r=0.130, P=0.66). In orchard no. 11, harmful oxydemetonmethyl and moderately harmful chinomethionate were sprayed 87 and 36 days before sampling, respectively; 93 phytoseiids/100 leaves were detected on sprayed apple trees (Table 4). In orchards no. 3,4, and 13, phytoseiid mites were extremely scarce on sprayed apple trees, although the intervals between last sprays and sampling dates were considerably long. Only low numbers of phytoseiid mites were encountered on adjacent non-orchard plants around these orchards, in contrast to orchard no. 11. In orchards no. 2,7, 9, and 10, sprays were applied 27-31 days before sampling; only a few phytoseiids were detected in orchard trees, although some of the adjacent plants exhibited high phytoseiid densities (Table 4). On the adjacent vegetation in orchards no. 2 and 10, the dominant phytoseiid was Euseius finlandicus (Oudemans) which was found on individual horse chestnut trees. In orchards no. 7 and 9, the dominant species in surrounding plants was Phytoseius macropilis (Banks). In orchard no. 12, Anthoseius rhenanus (Oudemans) dominated on adjacent plants, but on unsprayed apple, P. macropilis and E. finlandicus were dominant. P macropilis was the dominant phytoseiid species on unsprayed apple trees and E. finlandicus on sprayed apple trees (Table 2). These two species also dominated on most of the non-orchard trees and bushes. A. rhenanus was more numerous on surrounding vegetation than on apple trees. 5 Seiulus aceri (Collyer) was the only specific species detected and was found only on maple (Acer plalanoides L.) (Table 4). The numbers of phytoseiids on apple trees in a 2-ha orchard varied in August 1991, depending on the location of sample collection (Table 5). In the northern and eastern sectors of the orchard, where the phytoseiid numbers were highest, the adjacent plants comprised hazel (N, E), tall limes (E) and oaks (N), whereas the western sector consisted of bird cherry and great sallow (Salix caprea L.) were present. E. finlandicus occurred in greater numbers than any other phytoseiid on all plants; only ca. 5% of the specimens belonged to P. macropilis on sprayed apple trees. The main surrounding vegetation included six tree or bush species on which the phytoseiid density varied between 0.77 - 21.35 per gram of leaves. The predator-prey ratio at sampling, when counting only mobile spider mites and tydeid mites as prey, ranged between 1:0.52 - 1:2.78 on apple trees (primarily spider mites), and between 1:0.01 - 1:0.36 on other plants (primarily tydeid mites). The only exception was bird cherry trees, where the ratio was 1:5. Eriophyid mites (Acari: Eriophyidae) occurred commonly on apple trees and on most of the surrounding trees. When total phytoseiid numbers per plant specimen in the area were estimated, oak and lime appeared to be superior because of their large size, although the phytoseiid density per leaf or per gram of leaves was much higher on hazel bushes (Table 5). In samples taken in July 1992, phytoseiid densities on the lower and higher leaves of trees did not differ much; on lime 0.8/leaf in lower parts of the tree vs. 1.2/leaf on higher parts of the tree; on oak, 1.3/leaf vs. 1.1/leaf, respectively. DISCUSSION The data presented on species composition and densities of phytoseiids does not reveal any apparent highly consistent trend in terms of direct influence of adjacent vegetation on phytoseiid communities on sprayed apple trees. However, the results do allow some preliminary conclusions. P. macropilis was the predominant species on all unsprayed apple leaf samples. E. finlandicus was subdominant. In Canada, E. finlandicus and P. macropilis are also common on abandoned apple trees (Amano and Chant, 1990). Unsprayed apple trees provide very good habitats for many phytoseiid mites. In the present study, they were generally inhabitedby several species. In practical cultivation, a small separated area of unsprayed densely planted apple trees could be used as a phytoseiid reservoir from which shoots with high numbers of phytoseiid mites could be distributed 6 into the orchard by hand. This type of distribution has been practiced in Switzerland (Wildbolz and Staub, 1986). The value of these two dominant phytoseiid species as natural enemies of the European red spider mite differs with species. According to Dicke et al. (1988, 1990), E. finlandicus prefers the apple rust mite Aculus sclechtendali (Nalepa); its larval stage even suffered severe mortality when fed exclusively European red spider mites. P. macropilis preys readily on spider mites as well. Both phytoseiid species have wide ranges of food, including different phytophagous mites, pollen, fungi and plant fluids (Kropczynska-Linkiewicz, 1973). Because both species prey at least to some extent on spider mites, they are considered useful as natural control agents of the European red spider mite. The two dominant phytoseiid species on apple trees have distinctly different locomotor habits as observed in the laboratory. E. finlandicus moves quickly and is very active, whereas P. macropilis moves slowly and tends to spend longer periods crouching near veins and beneath hairs. As active movement of phytoseiids is limited, locomotor migration from surrounding plants to apple trees is unlikely to explain the presence of phytoseiids on apple trees in substantial numbers a few weeks after a harmful dimethoate spray (cf. Sabelis and Dicke, 1985). Therefore long-range passive aerial dispersal is considered to be a much more important means of entry into the orchards studied. Dispersal from understory cover plants onto orchard trees is probably not common, because both E. finlandicus and P. macropilis overwinter on trees in Finland, and have not been found in numbers on grasses (Tuovinen, unpublished). Hoy et al. (1985) documented aerial dispersal of Metaseiulus occidentalis Nesbitt at least 200 m in distance from source trees. Studies on M. occidentalis have revealed special behaviors that facilitate aerial dispersal by wind (Johnson and Croft, 1976, Hoy et al., 1984). Dunley and Croft (1990) studied the migration of M. occidentalis and T. pyri from source trees and discovered that M. occidentalis immigrated and colonized new downwind trees faster than T. pyri. A possible reason for lower aerial dispersal of T. pyri is concluded to be its limited movement compared to M. occidentalis. Lack of food may also release behavior that facilitates phytoseiid dispersal (Hoy et al., 1984), There are no similar studies for E. finlandicus or P. macropilis. However, on account of the higher activity level of E. finlandicus, it may disperse rapidly from adjacent plants during windy weather. This would better explain the difference in dominant species observed on unsprayed compared with sprayed apple trees than would a possible development of resistance to pesticides in E. finlandicus. Previous observations in many Finnish orchards have shown that immediately after the spraying of harmful pesticides, éither no or extremely few active phytoseiid mites can be found 7 (Tuovinen, unpublished). Hence, no resistance is expected to have developed in the species which occur in Finnish orchards. Similarly, Thistlewood (1991) found E. finlandicus on untreated apple trees and in some fungicide-treated apple orchards, but P. macropilis only in abandoned orchards. However, possible resistance to azinphosmethyl and dimethoate in some strains ofE finlandicus is currently being studied (T. Kostiainen, Univ. of California, Berkeley, personal communication). The presence of specific prey species is not a prerequisite for the most common phytoseiid mite species, E. finlandicus and P. macropilis (Tuovinen and Rokx, 1991). In this study, the presence of mobile spider mites and tydeid mites was taken into consideration. High numbers of phytoseiids were found even in samples with very low prey densities. The capability of many phytoseiids, e.g. E finlandicus, to survive without any animal prey has been noted also by Dicke et al. (1990). This capability may explain the overall distribution of E. finlandicus and P. macropilis in different habitats. Birch (Belula spp.) pollen, which is good food for E. finlandicus (Schausberger, 1991), is available on leaves of many plants and may serve as food for long periods. The phytoseiid species composition on sprayed trees appeared to correspond to that on adjacent vegetation in some but not all of the orchards studied. Differences may be attributed to the diverse types and structure of the surrounding vegetation. Future studies, in which data was gathered on the number of trees or bushes around orchards, information on mite densities and prevailing wind direction would be necessary for predictive purposes. It is, however, obvious on the basis of this study that the presence of tall trees, such as oak and lime, which E. finlandicus inhabits, offers a good opportunity for rapid phytoseiid aerial migration onto apple trees. Because phytoseiids inhabit the entire tree canopy, they may be abundant on higher leaves, where air movement is greatest. Other good host plants, such as hazel, may also be important phytoseiid sources, especially if hazel bushes are situated near apple orchard trees. Boiler et al. (1988) also concluded that hazel bush hedges may serve as a reservoir of phytoseiid mites in vineyards. In practice, the presence of various deciduous trees or bushes around orchards could facilitate phytoseiid colonization of orchards after toxic insecticide or acaricide treatments, thus improving the natural control of the European red spider mite. ACKNOWLEDGEMENTS I am grateful to Prof. Ron Prokopy for an invitation to the symposium and help in preparing the manuscript. I thank Dr. Diane Alston, Dr. Donn Johnson and Dr. Robert L. Bugg for comments on the manuscript. 8 REFERENCES Amano, H. and Chant, D.A., 1990. Species diversity and seasonal dynamics of Acari on abandoned apple trees in southern Ontario, Canada. Exp. Appi. Acarol., 8: 71-96. Boiler, E.F., Remund, U. and Candolfi, M.P., 1988. Hedges as potential sources of Typhlodromus pyri, the most important predatory mite in vineyards of northern Switzerland. Entomophaga, 33: 249-255. Boiler, E., Bigler, F., Bieri, M., Häni, F. and Stäubli, A., 1989. Nebenwirkungen von Pestiziden auf die Nutzlingsfauna wirtschaftlichen Kulturen. Shcweiz. Landw. Fo., 28: 3-40. Collyer, E., 1964. A summary of experiments to demonstrate the role of Typhlodromuspyri Scheut. in the control of Panonychus ulmi (Koch) in England. Acarologia, Proc. First Int. Congr. Acarology, Fort Collins, Colorado, USA, 1963: 363-371. Dicke, M., Sabelis, M W. and de Jong, M., 1988. Analysis of prey preference in phytoseiid mites by using olfactometer, predation models and electrophoresis. Exp. Appi. Acarol., 5: 225-241. Dicke, M., Sabelis, M.W., de Jong, M. and Alers, M.P.T., 1990. Do phytoseiid mites select the best prey species in terms of reproductive success? Exp. Appi. Acarol., 8: 161-174. Dunley, J.E. and Croft, 8.A., 1990. Dispersal between and colonization of apple by Metaseiulus occidentalis and Typhlodromus pyri (Acarina; Phytoseiidae). Exp. Appi. Acarol., 10: 137-149. Genini, M. and Baillod, M., 1987. Introduction de souches resistantes de Typhlodromus pyri (Scheuten) et Amblyseius andersoni Chant (Acari: Phytoseiidae) en vergers de pommiers. (Summary: The introduction of resistant strains of Typhlodromus pyri (Scheuten) and Amblyseius andersoni Chant (Acari; Phytoseiidae) in apple orchards.) Rev. Suisse Viticult. d'Arboricult. d'Horticult., 19: 115-123. Hassan, S.A., Bigler, F., Bogenschutz, H. Boiler, E., Brun, J., Calis, J.N.M., Chiverton, P., Coremans-Pelseneer, J., Duso, C., Lewis, G.8., Mansour, F., Moreth, L. Oomen, P.A., Overmeer, W.P.J., Polgar, L., Rieckman, W., Samsoe-Petersen, L., Stäubli, A., Sterk, G., Tavares, K., Tuset, J.J. and Viggiani, G. 1991. Results of the fifth joint pesticide testing programme carried out by the IOBC/WPRS-working group "Pesticides and Beneficial Organisms". Entomophaga, 36: 55-67. Hoy, M.A., van de Baan, H E, Groot, J.J.R. and Field, R.P., 1984. Aerial movements of mites in almonds: implications for pest management. Calif. Agric., Sept. 1984; 21-23. Hoy, M., Groot, R. and van de Baan, H.E., 1985. Influence of aerial dispersal on persistence and spread of pesticide-resistant Metaseiulus occidentalis in California almond orchards. Entomol. Exp. Appi., 37: 17-31. 9 Hoyt, S.C., 1972. Resistance to azinphosmethyl of Typhlodromus pyri (Acarina: Phytoseiidae) from New Zealand. N.Z. J. Science, 15: 16-21. Johnson, D.T. and Croft, 8.A., 1976. Laboratory study of dispersal behaviour of Amblyseius fallacis (Acarina: Phytoseiidae). Ann. Entomol. Soc. Am., 69: 1019-1023. Karg, W, Gottwald, R. and Freier, 8., 1987. Die Selektivität von Pflanzenschutzmitteln und ihre Bedeutung. Nachr.-81. Pflanzenschutzd. DDR, 41: 218-223. Karg, W., 1991. Die Raubmilbenarten der Phytoseiidae Berlese (Acarina) Mitteleuropas sowie angrenzender Gebiete. Zool. Jb. Syst, 118; 1-64. Kropczynska-Linkiewicz, D., 1973. Studies on feeding of four species of phytoseiid mites (Acarina: Phytoseiidae). In: Daniel, M. and Rosicky, B. (Eds), Proc. 3rd Int. Congr. Acarology, Prague, 31 August-6 September 1971, pp. 225-227. Czechoslovak Academy of Sciences, Prague. Kropczynska, D. and Tuovinen, T., 1988. Occurrence of predatory mites (Acari: Phytoseiidae) on apple trees in Finland. Ann. Agric. Fenn., 27: 305-314. MacPhee, A.W., 1963. The effect of low temperatures on some predaceous phytoseiid mites, and on the brown mite Bryobia arborea M. & A. Can. Entomol., 95: 41-44. Miedema, E., 1987. Survey of phytoseiid mites (Acari: Phytoseiidae) in orchards and surrounding vegetation of north-western Europe, especially in the Netherlands. Keys, descriptions and figures. Neth. J. PI. Path. Suppl., No 2: 1-64. Overmeer, W.P.J. and van Zon, A.Q., 1983. Resistance to parathion in the predacious mite Typhlodromus pyri Scheuten (Acarina: Phytoseiidae). Meded. Fac. Landbouwwet. Rijksuniv. Gent, 43; 247-251. Sabelis, M W. and Dicke, M., 1985. Long-range dispersal and searching behaviour. In: Helle, W. and Sabelis, M W. (Eds.) World Crop Pests. Spider mites. Part 1 8., pp. 141-160. Elsevier, Amsterdam. Schausberger, P., 1991. Vergleichende Untersuchungen zum Lebensverlauf, die Erstellung von Lebenstafeln und die Vermehrungskapazität von Amblyseius aberrarts Oud. und Amblyseius finlandicus Oud. (Acari: Phytoseiidae). Pflanzenschutzberichte, 52: 53-71. Thistlewood, H.M.A., 1991. A survey of predatory mites in Ontario apple orchards with diverse pesticide programs. Can. Entomol., 123; 1163-1174. Trapman, M., 1989. Integrierte Bekämpfung von Roter Spinne und Rostmilben im Obstbau - holländische Erfahrungen. Besseres-Obst, 34: 1, 8-10, 10 Tuovinen, T. and Rokx, 1991. Phytoseiid mites (Acari: Phytoseiidae) on apple trees and in surrounding vegetation in southern Finland. Densities and species composition. Exp. & Appi. Acarol., 12; 35-46. Wildbolz, T. and Staub, A., 1986. Raubmilbenansiedlung im Obstbau. Schweiz. Z. Obst-Weinbau, 122: 483-488. 1 1 10 0.2 0.2 1 1 0.2 1 20 0.2 1 1 1 20 10 0.2 0.2 0.2 0.2 0.2 1 10 1 0.2 1 0.2 0.2 1 0.2 20 TABLE 1 Surveyed orchards in 1989. Pesticide treatments and sampled adjacent plants. Pesticide treatments Adjacent vegetation (no. of sprays; days elapsed to sampling) Orchard, location Sampl date Insecticide 1 Acaricide2 Fungicide 3 Species 1. Lohja 9.8. azin(l;4s) chin(l;4s) oxyd(l;89) bite(3;7o) dith(4;29) dith(s;27) trif(4;s4) dith(6;2B) trif(2; 101) Acer platanoides L. 10 2. Lohja 9.8. oxyd(l;86) chin(l;27) Aesculus hippocastanum L. Pyrus communis L. 10 3. Lohja oxyd(l;85) dico(l;76)9.8. Alnus sp. Fraxinus excelsior L. Rosa majalis Herrm. Salix sp. Prunus cerasus L. 5> Prunus domestica L. 4. Lohja 10.8. azin(l;s3) oxyd(2;69) bite(l;s3) dith(l;63) trif(2;69) bite(s;s4)5. Lohja 10.8. azin( 1;54) chin( 1 ;54) Crataegus coccinea hort. Prunus padus L. Tiliä cordata Mill, none6. Aland 17.8. azin(2;34) dime(2;66) oxyd(l;66) bite(2;73) dich(2;73) dith(2;34) trif(l;100) bite(l;94) dich(l;3l) dith(6;3B) dith(6;3s) 7. Aland 17.8. azin(l;66) dime(l;sl) Corylus avellana L. 8 Aland 17.8 azin(l;73) chin(2;2l) dime(3;s9) P. domestica Sorbus sp. P. cerasus9. Aland 17.8. azin(2;62) chin(l;37) bite(6;29) chlo(l;29) Ulmus glabra Huds. A. hippocastanum Ribes uva-crispa L. Sambucus racemosa L. 10. Aland 17.8. azin(l;2B) chin(l;34) dime(2;4B) bite(3;2B) copp(l;l 14) dich(2;72) dith(2;4B) bite(6;44)11. Piikkiö 25.8. oxyd(l;87) chin(2;36) Cornus alba L. Ribes nigrum L. Rubus sp. Sorbus sp. 12. Bromarv 31.8. oxyd(l;>100) dioo(l;70) bite(l;>80) pine(2;47) dich(l;>80) dith(9;>4s) A. platanoides Alnus glutinosa (L.) Rubus idaeus L. Sorbus aucuparia L. C. avellana13. Pohja 6.9. azin(2;6s) chin(l;96) bite(2;sl) dith(s;6s) dith(9;47) R. nigrum P. padus14. Pohja 6.9. dime(l;l23) flub(l;106) Rubus odoratus L. U. glabra ' Insecticides: azmphosmethyl, dimethoate. oxvdemetonmethvl 2 Acaricides: chinomethionate. chlorbenzilate. dicofol. fenson. flubenzimine. pine-oil soap. 3 Fungicides: bitertanol. copperoxvchlonde. dichlofluanid. dithianon. triforine. 4 Coefficient based on the approximate size of plants (e.g. 0.2 = 1/5 the size of normal apple tree) 5 Sprayed with oxydemetonmethyl. TABLE 2 Composition of all identified specimens of phytoseiids on apple trees and adjacent plants at 14 orchards in August-September, 1989 (n = 1711). % of each species of Phytoseiidae on Unsprayed Sprayed Other apple apple plants 0 FAMILY PHYTOSEIIDAE Berlese (n=737) (n=2o3) (n=77l) Subfamily Phytoselinae Berlese Phytoseius Ribaga Phytoseius macropilis (Banks) Seiulus Berlese Seiulus aceri (Collyer) Paraseiulus Muma Paraseiulus soleiger (Ribaga) Paraseiulus triporus (Chant & Shaul) Anthoseius De Leon Anthoseius richteri (Karg) Anthoseius rhenanus (Oudemans) Typhlodromus Scheuten Typhlodromus laurae Arutunjan Subfamily Amblyseiinae Berlese Euseius Wainstein Euseius finlandicus (Oudemans) Amblyseius Berlese Amblyseius reductus Wainstein 67.130.1 24.7 0.00.0 1.1 1.08.5 0.9 0.45.7 1.7 0.30.0 0.4 0.40.0 10.6 0.00.0 0,1 30.853.5 60.5 0.02.2 0.1 0 Only part of specimens collected on other plants were identified. TABLE 3 Densities of phytoseiid mites on unsprayed apple trees and on adjacent trees bushes (1989-1991). and Phytoseiid mites/100 leaves Plant species Mean ±SE No. of samples Apple ( Malus x domestica Borkh.) Acer platanoides 130.0 20.1 26.8 10.5 28 4 Aesculus hippocastani 1062.7 463.9 3 3Alnus spp. 1.3 0.7 Be tula spp. 15 0.0 4 Corylus avellana Crataegus coccinea Fraxinus excelsior Prunus padus 288.3 106.7 21.0 0.6 8 3 254.0 160.3 46.2 25.1 3 5 Quercus robur Ribes nigrum Ribes ruhrum L.° Rubus idaeus 122.3 3.9 67.9 57.7 30.3 13.5 29.9 17.0 30.6 14.7 3 8 11 7 Salix spp. Sorbus spp. Tiliä spp. 5 5126.4 60.5 122.0 30.7 115.0 68.0 7 2Ulmus glabra 15 Not included in samples in 1989 TABLE 4 Phytoseiid mites on apple and adjacent trees and bushes in 14 orchards, 1989. (Cf. the phytoseiid species list in Table 2 and the plant species list in Table 1). Number of phytoseiids/100 leaves^ Unsprayed apple Sprayed apple Surrounding trees and bushes (unsprayed) Orch. no. Phytoseiid Phytoseiid species n Phytoseiid species n Plant species n species present 2 GROUP 1 5. P.sole 8.3 P.macr 1.3 E.finl I E.finl 52 P.macr 31 P.trip 7 P.sole 2 A.redu I E.finl 16.3 P.macr 4.3 P.sole 0.7 P.trip 0.7 C. coccinea P. padus 22 E.finl 9 E.finl T. cordata C. alba 73 E.finlfi.rhen.P.sole 77 E.finl11. P.macr 86 E.finl 46 P.sole 5 A.rhen 1 469 E.finl,P.sole,P.macr.T.laur 3 P.macr,E.finl R. nigrum Rubus sp. S. thuringiaca 111 E.finl,P.sole,P.macr 14. P. padus 141 E.finl,P.macr 272 E.finl,P. tripR. odoratus U. glabra 47 E.finl,P.sole,P. trip GROUP 2 2. P.macr 28 E.finl 1 P.macr 4 A.rhen I P.macr 2 E.finl 2 A. hippocastanum P. communis 140 E.finl 1 E.finl 7. 0 C. ave liana 153 P.macr,P.trip,P.sole 9. A.redu 1 E.finl I P. cerasus U. glabra 4 P.macr,E.finl,P.trip 183 P.macrfi.redu 10. 0 A. hippocastanum R. uva-crispa 1440 E.finl,P.trip,P.macr 4 E.finl,P.trip 0 - 0 - 2 A.rhen S. racemosa A. platanoides A. glutinosa R. idaeus P.macr 118 E.finl 49 A.rhen I12. 49 P.sole 2 15 A.rhen A.rhen I S. aucuparia 334 A.rhen,P.macr,E.finl. A.richt,P.sole GROUP 3 1. P.macr 135 P.trip 3 P.macr 2 A. platanoides 20 S.acer,E.finl 3 3. 0 Alnus sp. 0 F. excelsior Rosa sp. 28 E.finl 0 Salix sp. I E.finl 4. E.finl I P. cerasus 3 A.rhen,E.finl 0P. domestica P. domestica Sorbus sp. 8. 0 0 0 6. 13. E.finl 59 0 P.macr 125 E.finl 71 E.finl 0.5 P.sole 0.5 C. avellana R. nigrum 4 E.finl 5 E.finl71 A.rich 2 1 - no unsprayed apple trees in the orchard 2 Descending order in abundance. TABLE 5 Densities of phytoseiid mites and prey mites (spider mites and tydeid mites) on apple trees and on adjacent trees in a 2 ha apple orchard. Samples were taken on August 6, 1991, from trees in northern (N), eastern (E), and western (W) parts of the orchard. All apple trees were sprayed with dithianon (11 sprays, the last spray on July 1), chinomethionate (June 12) and dimethoate (July 22). (Cf. the phytoseiid species list in Table 2). Phytoseiid mite numbers Prey density Pred ; /leaf prey 3.58 2 1 : 1.15 0.97 2 1 : 0.52 0.89 2 1 : 2.78 1.39 1 : 0.14 0.02 1 : 0.01 0.78 1 : 0.36 0.3 1 : 0.26 0.04 1 : 0.05 1.26 1 : 5.04 Phytoseiid speciesSample /leaf /gram /plant 1 Apple (N) E.finl,P.macr 3.12 4.46 11200 1.85 2.68 6700Apple (E) E./inl,P.macr Apple (W) E.finl,P.macr 0.32 0.44 1100 Corylus avellana (E,N) E.jinl.P.macr 9.82 21.35 10800 Lonicera xylosteum L. (N) E./inlr A.redu,P.macr 2.66 14.0 3500 Tiliä cordata (E) E.fml 2.42 2.95 147500 Quercus robur (N) E.fml 1.17 2.93 146500 Salix sp. (W) P.macr,E.fml.P.sole 0.8 0.77 200 E.fml 0.25 0.86 2200Primus padus (W) ' Estimated fresh weights of all leaves of one average plant in the area; apple 2.5 kg, C. avellana 0.5 kg, Salix sp. 0.5 kg, P. padus 2.5 kg. L. xylosteum 0.25 kg. Q. robur 50 kg, T. cordata 50 kg. 2 Primarily P. ulmi. Mean no. of P. ulmi winter eggs in November 1991 was 2.6/10 cm in twig samples taken randomly from the whole orchard. IVANNALES AGRICULTURAE FENNIAE, VOL. 28: 317—333 (1989) Serla ANIMALIA NOCENTIA N. 142 Sarja TUHOELÄIMET n ; o 142 CHEMICAL CONTROL OF EUROPEAN RED SPIDER MITE PANONYCHUS ULMI (KOCH). I. EVALUATION OF FLUBENZIMINE Tuomo Tuovinen Tuovinen, T. 1989. Chemical control ofEuropean red spider mite Panonychus ulmi (Koch). I. Evaluation of flubenzimine. Ann. Agric. Fenn. 28: 317—333- (Agric. Res. Centre, Inst. PI. Protect., SF-31600 Jokioinen, Finland.) Good control of P. ulmi was achieved with flubenzimine (150—250 g a.i./100 1 water, 0.45—0.75 kg a.i./ha, mistsprayer 300—400 l/ha) when sprayed just before or dur- ing blossom and, if necessary, in late June or July. If sprayed only once, the recom- mended time for spraying in spring is when the effective temperature sum of 200 dd above + 5 °C has been reached. A high density mite population may need another spray later in July. Later treatments result in a low overwintering population, facilitating mite control also in the next season. When sprayed in low concentra- tions (25 —85 g a.i./100 I water) several times, almost complete control of P. ulmi was achieved. Flubenzimine was also effective against the apple rust mite Aculus schlcchtcndali. It had a harmful effect on predatory phytoseiid mites and one spray diminished the number of phytoseiids by more than 90 %; when flubenzimine was sprayed several times during the season, phytoseiids disappeared almost entirely. Flubenzimine reduced the number of spiders (Araneida) but had only slight effect on the numbers of predatory amhocorid bugs. The reference acaricides chinomethionate (37.5 —62.5 g a.i./100 I water, 0.12—0.22 kg a.i./ha), dicofol (140 g a.i./100 I water, 0.4 kg a.i./ha), fenbutatinoxide (250 g a.i./ 100 I water, 0.75 kg a.i./ha) and oxydemetonmethyl (132 g a.i./100 I water, 0.4 kg a.i./ha) were generally not as effective as flubenzimine. In most cases, satisfactory control can be achieved also by thesecompounds, but often two or even three treat- ments are then necessary. Index words: chinomethionate, dicofol, fenbutatinoxide, flubenzimine, oxydemeton- methyl, acaricides, European red spider mite, Panonychus ulmi, Phytoseiidae. INTRODUCTION The European red spider mite (ERM), Panony- chus ulmi (Koch), has become a more serious pest on commercially grown apple trees in Fin- land. The ERM control strategy with regard to chemical control, is to lower the population in the spring before the beginning of fruit de- velopment cither by early spring sprays with ovicidal oil preparates, pre-blossom sprays with organophosphate insecticide oxydemeton- methyl, or pre-blossom and blossom sprays with chinomethionate and dicofol. However, in many cases additional sprays are required in July. Growers are aware of the common de- mand to reduce pesticide use, but so far, no acaricide has provided good control with a single spray, especially, if the season is warm and favourable for ERM. Successful biological control methods against 317 main insect pests would resolve the major problems in ERM control. In particular, insec- ticides have adverse effects on phytoseiid mites and other beneficial arthropods (e.g. Swift 1968, Karg et al. 1987). In small home gardens where no insecticidal, acaricidal or fungicidal treatments have been carried out, ERM is not a problem. This is mostly due to predatory phytoseiid mites which are common in these orchards (Kropczynska and Tuovinen 1988). In Finland, the main insect pest on apple is the apple fruit moth Argyresthia conjugella Zell,, which is controlled by spraying broad-spec- trum insecticides. Studies on the integrated control of the apple fruit moth are in progress, but before any successful methods are available, the use of acaricides against ERM will continue. The most common acaricides, chinomethionate and dicofol, have been also found to have harmful effect on phytoseiids (Hassan et al. 1987). Effective, yet safer for natural enemies, acar- icides would be of great importance in Finnish conditions where apple gardens are quite small and surrounded by wild herbaceous trees and bushes from which predators may easily move to apple trees. Flubenzimine, which acts as a chitin synthesis inhibitor (Zoebelein et al. 1979), is an interesting acaricide owing to a different mode of action compared to that of earlier acaricides. In some earlier tests, fluben- zimine has proved to be quite harmless to beneficial insects and predatory mites, thus sup- porting possible use of the compound in inter- grated control (Boness 1983). Chinomethionate, dicofol or oxydemetonmethyl were included in tests. The gim of this study is to combine the results of the field tests with flubenzimine and to summarize the situation of ERM control in Finland. MATERIAL AND METHODS Flubenzimine was used as 50 % WP formula- tion Cropotex, produced by Bayer. As reference products, chinometionate as 25 % WP formulation (Morestan, Bayer), dicofol as 18.5 % WP formulation (Kelthane, Rohm and Haas), fenbutatinoxide as 50 % WP formulation (Torque, Shell) and oxydemeton- methyl as 26.5 % liquid formulation (Meta- systox, Bayer) were used. Sprays were carried out using the recommended concentrations and doses. Experimental orchards Experiments were carried out in four orchards in 1981—88. Two of the orchards were com- mercial cultivations where insecticidal and fun- gicidal sprays were performed, too. Pohja 1981—84. A commercial orchard com- prising 7 ha of apple trees. The location is situ- ated near the southern coast. The experimen- tal area was 0.5 ha and the main cultivar ’Lobo’. The area was divided into 6 two-row sectors, each including about 60 trees. 10 trees per sec- tor were randomly chosen for sampling leaves and twigs. Treatments were carried out by a tractor-driven mistsprayer (Hardi). Some insec- ticidaland fungicidal sprays were performed in 1982—1984. The nearest meteorological sta- tion is Salo (36 km). Pälkäne 1982—86. The experimental area, consisting of 100 apple trees (cv. Huvitus), was part of the Häme Research Station orchard. A randomized block design with four 4-tree rep- licates and untreated shelter trees between treat- ments was used in 1982 and 1986, in 1983—84 the single tree replicates (3 —12) employed were arranged in groups according to the treat- ments in the previous year. Treatments were done with a knapsack mistsprayer (Solo). A 318 meteorological station is situated 0.3 km from the experimental area. Bromarv 1986. An experiment was carried out in a commercial orchard using two 1 ha blocks. Sprays were performed using a tractor- driven mistsprayer, and insecticidal and fungi- cidal sprays were also carried out. Jokioinen 1988. An experiment in an ex- perimental orchard was performed using fully randomized design and single trees as rep- licates. Sprays were done with a knapsack com- pression sprayer and a knapsack mistsprayer. Sampling and observations Normally, sampling was carried out by collect- ing s—lo5—10 spur leaves/tree, from 10—20 trees per treatment, selected randomly from each tree from the same height (1.5—2 m). Sampling was performed usually once before spraying and 2 —6 times afterwards. Leaves from each tree were kept separately in plastic bags and stored at +5 °C temperature. Numbers of liv- ing mobile mites and eggs were counted im- mediately or after I—3 days under a stereo- microscope. During inspection, occurrence of natural enemies was also observed. Samples of twigs were collected to count winter eggs: 5 pieces of 20 cm 2—3 year old branch from 10—20 trees per treatment were collected in late October and in November. In 1982, samples of arthropods occurring in trees were collected by beating 10 branches (in 10 trees/treatment) over a sampling net with an opening of 0.1 m 2. Samples were preserved in alcohol and studied later. Monthly effective temperature sums (in day- degrees over +5 °C) were recorded by the nearest weather stations (Figs. I—2). The significance ofdifferences between treat- ments (in Pohja and Pälkäne) was tested by analysis of variance using Duncan’s multiple range test (Steel and Torrie 1980) on log(x + 1)- transformed data for each checking date both for eggs and mobile stages. In other orchards, the t-test or analysis of variance using Duncan’s multiple range test was employed for calcula- tion. All calculations were performed using the SPSSX-statistical package. Fig. 1. Monthly effective temperature sums in day-degrees above +5°C at the Salo meteorological station, 1981—1984. 319 RESULTS Pohja Results of the leaf and winter egg counts from Pohja are arranged in a continuous series of ex- periments to show the yearly changes in mite density after different treatments (Figs. 3a and 3b). In 1981, two sprays with flubenziminekilled ERM almost completely (block A). One late ap- plication (8.7., block C) had a similar effect for the rest of the season. One early spring appli- cation (27.5., sprayed when 189 day-degrees above + 5 °C was reached, block B) had a long lasting effect also although the number of mo- bile mites was significantly higher than in other trees sprayed with flubenzimine. Chinometh- ionate (blocks D-F) also had a good effect al- though the numbers of mobile mites and sum- mer eggs were higher than in respective fluben- zimine treated trees. Winter egg counts show that the late application of both acaricides resulted in significantly lower egg numbers than the earlier applications. In 1982, block A, sprayed in -81 twice with flubenzimine, was left as a non-treated block because of low ERM density. Although not sprayed, the number of mites did not exceed the control threshold of 10 mites/leaf before September. Flubenzimine was applied once, on 1.6. (140 dd, block B) and on 28.6. (blocks D and F). In block B, ERM density was quite high but one spray was enough to maintain the num- ber of mites under 5/leaf until August. The later applications resulted in almost the same popu- lation level in September. Chinomethionate, when sprayed on 1.6, (block E) did not have as good an effect as flubenzimine, although the initial ERM population was lower. In the un- treated blocks (A and C), which had the late spray with flubenzimine in the previous year, the number of ERM stayed under 10 mobile mites/leaf throughout the whole season. According to the summer egg counts (Fig. 3b) there were three complete ERM generations in 1982. The effective temperature sum of the Fig. 2. Monthly effective temperature sums in day-degrees above +5°Cat the Pälkäne research station, 1982—1984, 1986. 320 whole season was 1313 dd, which is about the normal rate (mean 1951—1980). In other years, no clear picture of the numbers of generations could be obtained because of fewer inspec- tions. In 1982, beat samples were collected from each block to check the occurrence of other arthropods. Very few beneficial insects belong- ing to Heteroptera, Neuroptera or Coleoptera (Coccinellidae) as well as spiders (Araneida) were caught (Table 1). No doubt this is due to a spray with dimethoate against the codling moth Cydia pomonella (L.) and the apple fruit moth Argyresthia conjugella. In 1983, oxydemetonmethyl was sprayed over the whole experimental area (23.5., 190 dd). Furthermore, one spray with flubenzimine was performed on 26.5. (220 dd, blocks A, D and F). The initial numbers of ERM in each block were quite low and stayed low during June, but ERM densities increased on a very high level in blocks treated only with oxy- demetonmethyl. The effect of flubenzimine lasted almost through the whole season, but later in the autumn ERM numbers increased which is expressed in the high numbers of winter eggs. In 1983, September was unusual- ly warm and favourable for ERM egg laying (Fig. 1). In 1984, only flubenziminewas sprayed over the whole experimental area (24.5., 190 dd). ERM density remained low, except at the end of the season. The effective temperature sum of the season was higher than normal, 1461 dd, favouring ERM reproduction. Pälkäne The results of the experiments in Pälkäne are presented in Tables 3—6. Tables 4 and 5 are arranged so that also the treatments of the previous year are taken into account. In 1982, the initial ERM population was very uniform in the experimental area (Table 3). The effect of flubenzimine, when sprayed quite late (29.6.) was satisfactory.The numbers of mobile ERM in untreated blocks did not increase sub- stantially, which may be due to predatory bugs (Heteroptera: Anthocoridae) present in the or- chard. The weather was quite cold in 1982,and the effective temperature sum of the whole sea- son was only 1207 dd. No sprays with broad- spectrum insecticides were performed, but half of the trees were sprayed with diflubenzuron (Dimilin) which did not have any effect on mites during the season except on 2.8., when the number of mobile mites was even higher than in the control trees. In 1982, beat samples were collected to check the occurrence ofother arthropods than mites. Of the beneficial arthropods, Anthocoris spp. was found to be present in all blocks, but not in large numbers (Table 2). Spiders were quite common but flubenzimine clearly diminished their number. The apple sucker Psylla mali (Schmiedb.) (Homoptera: Psyllidae) was the most common insect pest; only a spray with diflubenzuron diminished the number of apple suckers to some extent. In 1983,ERM numbers were very high in late July, except on trees sprayed the previous year with flubenzimine (Table 4). Flubenzimine, fen- butatinoxide and a pyrethroid insecticide, del- tamethrin, were sprayed very late on 29.7. In trees treated with flubenzimine both in 1982 and 1983, or with fenbutatinoxide in 1983, ERM density in August and the number of winter eggs were significantly lower than in other blocks. Flubenzimine sprayed on trees with a high density of ERM (block B), while diminishing the numberof mobile stages, could not prevent winter egg laying later. The effect of fenbutatinoxide was not as good as that of flubenzimine. Although deltamethrin at first lowered mobile ERM numbers, it later caused a clear outbreak of ERM when winter egg num- bers are taken into consideration. The whole season was warm (1404 dd) and especially Sep- tember was warmer (190 dd) than usual which explains the high winter egg densities. 321 322 Fig. 5 a. Results from the field experiments at Pohja in 1981 —1984. Mean numbers of mobile mites (larvae, nymphs and adults) per one leaf and mean numbers of winter eggs/1 cm twig. Treatments (g a.i./l()0 I water) with a mistsprayer, 300 l/ha, on both sides of the rows. For apple scab control, dithianon (225 g a.i./100 1) was sprayed 5 —7 times/year. For moth control, dimethoate (120) was sprayed 20. 6. 1982 and 15. 6. 1984 and deltamethrin (10) was sprayed 2. 7. 1984. Significant differences (p = 0,05) according to Duncan's multiple range test on log-transformed data for each in- spection date. Other arthropods Anthocoridae Neuroptera Araneida (mites not included) Treatment: ABCDEFABCDEFABCDEFABCDEF li(. 0 12 12 3 0 0 0 0 0 0 110 0 12 75 36 62 76 31 50 28.6 4 2 0 0 10 0 0 0 0 0 0 0 1 1 0 0 0 18 12 7 13 6 9 26.7.10000I)000020 0 0 0 0 0 0 5 3 7 3 8 0 10 8 0 0 0 0 0 0 0 0 0 0 0 10 1 0 0 0 0 0 6 3 4 43 10 24.8. 0 0 0 0 1 0 0 0 0 0 1 4 0 0 1 0 2 3 14 4 12 13 13 9 323 Table 1. Number of some predatory and other arthropods collected by the beating method in Pohja 1982. Treatment letters refer to Fig. 3. Samples were collected from 10 branches/treatment. Fig. 3 b. Results from the field experiments at Pohja 1981—1984. Mean numbers of ERM summer eggs per one leaf Treatments as in Fig. 3 a. 324 325 Table 2. Number of predatory and other arthropods collected by the beating method in Pälkäne 1982. Treatment letters refer to Table 3. Samples werecollected from 10 branches/treatment. Other arthropods Anthocoridae Neuroptera Coccinelidae Araneida (mites not included) Treatment: ABCD ABCD ABCD ABCD ABCD 197. 3 8 10 10 0 0 0 0 0 0 0 0 0 1 6 7 72 14 10 26 16.8. 1250 0000 0121 3367 92 49 30 60 30.8. 5 12 11 5 1 1 0 1 1 0 6 0 21 20 39 25 129 121 56 75 Table 3- Results of the field experiment in 1982 (Häme Exp. Sta., Pälkäne). 0.3 —0.4 1/tree was sprayed with a knapsack mistsprayer. Numbers of mites were counted from 5 leaves/tree and numbers of winter eggs from 5 twigs/tree. Treatment and rate No. of mites/leaf (mobile and eggs) Winter (g a.i./100 1) eggs/10 cm 21.6. 6.7. 19.7. 2.8. 16.8. 30.8. Date ME ME ME ME ME ME A. Flubenzimine (150) 29.6. 7.7 19.5 I.IA 17.8AI.BA 6.4AO.OA 3.6A 3.7A 8.9A 1.7A 6.1A42. 5A B. Flubenzimine (150)+ 29.6. 9.2 18.6 0.7A 15.9A 2.9A 9.1A0.2A8 3 0A 3 3A 12.0A2.68 6.7A55.8 A Diflubenzuron (125) 13-7- C. Diflubenzuron (125) 13 7. 6.5 15.6 4.48 28.88 10.28 18.48 5 2C 20.28 15 9B 43-4B 12. 5C 29.88 164.08 D. No treatment 8.1 17.8 5.48 30.88 13. 5C 14.68 0.68 33. 7B 21.68 35. 3B 11.9C22. 2B 367,08 Means with different letters in columns denote significant differences (P = 0,05) according to Duncan’s multiple rangetest on log-transformed data. Columns without letters indicate a nonsignificant F-test (P = 0.05). 326 Table 4. Results of the field experiment in 1983 (Häme Res. Sta., Pälkäne). 0.3 —0.4 l/tree was sprayed with a knapsack mistspraycr, on 29.7. Numbers of mites were counted from 5 leaves/tree, and numbers ofwinter eggs from 5 twigs/tree. Treatment and rate Treatm. No. of mites/leaf (mobile and eggs) Winter (a a.i./l()() I) in 1982' eggs/10 cm 29.7. 17.8. ME ME A. Flubenzimine (250) A 6A 43A O.OA 11A 1 1A B. Flubenzimine (250) 448 24980.7A106BC 1048 C. Fenbutatinoxide (250) B 17A 56A 2 ha 39A 1968 D. Fenbuutinoxide (250) 71C 2708 1.7 A 778 C 389 C E. Deltamethrin (2.5) 358 82A I 108 68C 675 D F. No treatment 278 100 A 22.0C 1028 447CD Means with different letters in columns denote significant differences (P = 0.05) according to Duncan s multiple range test on log-transformed data. 1 Letters refer to table 3(— indicates untreated trees in 1982). In 1984, great differences in initial densities among groups of trees were found (Table 5). Except acaricides, the pyrethroids deltamethrin and cyfluthrin, and an insect growth regulator, diflubenzuron, were included to test their ef- fect on the apple fruit moth. All acaricides, sprayed on 11.6. (377 dd) had a good effect on ERM, and only small differences could be found in winter egg counts in the autumn. May was very warm (270 dd) favouring the rapid de- velopment of ERM, but in June, soon after the treatments, a colder period began, lasting sev- eral weeks. In addition to the sprays, cold weather might have influenced on mite num- bers, which later in the season remained quite low in all treatments. In 1985, the density ofERM was low and no experiments were carried out. In 1986, fluben- zimine was sprayed on 17.7. on two areas hav- ing different initial ERM densities (Table 6). Flubenzimine had a good effect for the rest of the season and winter egg numbers were very low. Also phytoseiid mites Euseius finlandicus (Oud.) and Phytoseius macropilis (Banks) (Acari: Phytoseiidae) were found to be present in the orchard. In trees sprayed with flubenzimine the number of predatory mites was much lower than that in untreated trees. Bromarv 1986 The effect of flubenzimine and chinomethionate was compared in a commercial orchard (Table 7). Flubenzimine was sprayed only once (30.5., 180 dd), and chinomethionate three times in May and June (first on 23.5., 147 dd). Neither flubenzimine nor chinomethionate gave satis- factory control of ERM. Jokioinen 1988 Flubenzimine was sprayed 5 times timed ac- cording to apple scab control sprays to study also the possible effect of sprays on the apple scab. The concentrations were lower than in other experiments, 25—85 g a.i./100 1 water, but the effect of the sprays on ERM was almost complete (Table 8). The initial population den- sity of ERM was low, but predatory mites E. fin- landicus and P. macropilis were numerous. Flubenzimine almost completely killed all mites, including phytoseiids and the apple rust mite Aculus schlechtendali (Nal.) (Acari: Eri- ophyidae). 327 Table 5. Results of the field experiment in 1984 (Häme Res. Sta., Pälkäne). 0.3 —0.4 1/tree was sprayed with a knapsack mistsprayer. Numbers of mites were counted from 5 leaves/tree, and numbers of winter eggsfrom 5 twigs/tree. Treatment and rate Date Treatm. No. of mites/leaf (mobile and eggs) Winter (g a.i./100 1) in 1983 1 eggs/10 cm S 11.6. 26.6. 7.8. 29.8. ME MEME ME A. Flubenzimine (250) 11.6. C O.BAB 12.0A8 0.4A8 0.4 O.OA O.OA O.IA 0.5A 4.3AC B. Flubenzimine (250) 11.6. E I.OAC 25.0AC 0.2A8 0.5 I.OBC 3.28 O.OA 0.3A 5.3AC C. Flubenzimine (250) 11.6. I.6AD 44.0AC O.IAB 0.0 0.2A8 0.6AO.OA 0.3A 2.BAC D. Flubenzimine (250)+ 11.6. B 2.4AD 45.08CO.OA 1.0 O.OA O.OA O.OA O.OA 0.4 A Deltamethrin (6.25) 10.7, E. Flubenzimine (250)+ 11.6. —3.68 D O.IAB 1.5 O.OA O.BA O.OA O.OA 1.3A8 Deltamethrin (6.25) F. Fenbutatinoxide (250) 11.6. —0.6 A 0.2A8 0.2 1.3C 0.6A 0.5AI.IA28.28 C G. Fenbutatinoxide (250) + 11,6. F 3.BCD 38.0AC 1.08 1.4 O.4AC O.IA 0.2AO.IA 14.28 C Diflubenzuron (125) 10.7. H. Fenbutatinoxide (250)+ 11.6. —2.7AD 105.0CO.IAB 0.0 O.IAB 0.3A 0.2A 2.1A8.48 C Diflubenzuron (125) I. Dicofol (139) 11.6. D 4.0D 32.0AC 0.5A8 0.6 O.3AC O.BAB 1.38 8.38 33.0 C J. Dicofol (139)+ 11.6. A I.OAC 5.1A8 O.OA 1.0 O.OA 0.2AO.OA O.OA 2.6A8 Flucythrinate (10) 10.7. K. Dicofol (139)+ 11.6. I.7AD 29.0AC O.IAB 0.0 O.IAB 0.4AO.OA 0.2A33AC Flucythrinate (10) 10.7. Means with different letters in columns denote significant differences (P = 0.05) according to Duncan’s multiple rangetest on log-transformed data. Columns without letters indicate a nonsignificant F-test (P = 0.05). 1 Letters refer to table 4 ( sign indicates untreated trees in 1983). 328 329 Table 6. Results of the field experiment in 1986 (Häme Res. Sta., Pälkäne). 0.5 1/tree was sprayed on 17.7. with a knap- sack mistsprayer, 10 trees/treatment. ERM and phytoseiid numbers were counted from 5 leaves/tree and numbers of winter eggs from 5 twigs/tree. T-test was calculated separately for the two areas with different initial ERM densities. Treatment and rate (g a.i./100 I) No. of mites/leaf (mobile and eggs) Winter eggs/10 cm 17.7. 14.8. M E Phyt. M E Phyt. Area 1. 6.8 36.3 1.8 7.6 25.3 0.3 N.S. 0.036 0.000 3.216.7 0,1 36.0 93 8 1.9 0.0000.000 0.000 A. Flubcnzimine (250) B. No treatments 3.7 142.5 T-tcst, P = Area 2. 0.000 A. Flubcnzimine (250) B. No treatments 1.4 8.4 0.2 3.4 17.1 0.1 0.000 0.003 N.S. 0.00.4 0.0 10.851.6 0.9 0.0000.000 0.013 3.7 56.0 T-test, P = 0.000 Table 7. Results of the field experiment in 1986 (Commercial orchard, Bromarv). Blocks of about 1 ha were sprayed with tractor driven mistsprayer (Hardi), 400 l/ha. Numbers ofmites (mobile and eggs) were counted from 5 leaves/tree, and winter eggs from 5 twigs/tree. Treatment and rate Date Mites/leaf Winter- (ga.i./lOOl) 4.7. eggs/10 cm M E A. Flubenzimine (150) 30.5. 8.74.1 336 B. Chinomethionate (55) 23.5,9.6,18.6. 12.15.0 478 C. Chinomethionate (55) 18.6. 2.0 31 56 Other treatments (all blocks): dimethoate (160 g a.i./100 I) 23.5. and 3.7., dithianon (225) 14.5., 23.5., 9.6., 23.6., 3 7. and 13.7. (for scab control). Table 8. Results of the field experiment in 1988 (Agricultural Research Centre, Jokioinen). Fully randomized apple trees (6 per treatment) were sprayed according to apple scab spraying program, with a compression sprayer, on 23-5., 3-6. and 15.6., and with a knapsack mistsprayer on 21.6. and 27.6. Samples of 20 leaves/tree were checked and number of mites were counted or estimated (Eriophyidac), Treatment and rate Number of mites/10 leaf (mobile and eggs) (g a.i./100 1) ERM Eriophyidae Phytoseiidae ME M M A. Flubenzimine (3x25, 2x85) 0.00.0 30A 0.03 A B. Clofentezine (3 x 25, 2 x 85)' 0.670.58 30A 35A C. Hexythiazox (3x5, 2x 17) 1 0.170.33 83.08 2.33 A D. Bitertanol (3 x 12.5, 2x42. 5)2 1.250.75 95.08 1958 E. No treatments 1.170.75 67.08 17.88 Means with different letters in columns denote significant differences (P = 0.05) according to Duncan s multiple range test on log-transformed data. Columns without letters indicate a nonsignificant F-test. New products, not analysed in this article (cf. Tuovinen 1990). Fungicide used against the apple scab. DISCUSSION The growth of ERM populations strongly de- pends on temperature. In Finland, ERM has usually 3, sometimes 4 yearly generations (Lisroet al, 1939). During these experiments, the total effective temperature sums varied be- tween 1030 dd in 1987 to 1520 dd in 1983. During the tests, manyfold differences in reproduction capacity of ERM due to tempera- ture variations between years could be expect- ed. The results of the experiments from vari- ous years are not directly comparable on the other hand, one or two years’ experiments may lead to erroneous conclusions as to the effect of acaricides on ERM. Because flubenzimine is most effective against immature stages of ERM (Zoebelein et al. 1980, Kolbe 1981), the timing of sprays is thought tobe important especially in early sea- son sprays. In an ideal situation, all winter eggs should have been hatched, but only larval or nymphal stages should be present at the mo- ment when spraying takes place. In practice, the hatching of winter eggs lasts, in Finnish con- ditions, 2—3 weeks depending on the tempera- ture and the position of eggs on branches (Listo 1939). According to Lees (1953) the threshold temperature for the embryonic post- diapause development of ERM winter egg is + 7 °C. In laboratory experiments (not pub- lished), 50 % ofERM winter eggs hatched when 200 dd above + 5 °C was reached. For practi- cal purposes, the commonly used plant growth threshold + 5 °C can be referred to and may approach the correct value in Finland (cf. Listo et al. 1939). In field tests, temperature sums, recorded in the nearest meteorological stations, varied from 130 to 377 dd in early season sprays. In most tests, winter eggs had begun to hatch but no summer eggs had been laid before the spray (exception: Pälkäne 1984, 377 dd, summer eggs were present in abundance). Good results were obtained with flubenzimine in all cases, except in Bromarv 1986 (180 dd). This orchard is situ- ated on a cape surrounded by the sea in spring the prevailing temperature is much colder than the inland temperature, where the temperatures were recorded. In this case, mites were not counted before spraying, but at least part of the winter eggs had already hatched. The later sprays in June and July usually resulted in low numbers of mobile ERM. The results show that flubenzimine has a long last- ing residual effect so that high numbers of sum- mer eggs present on leaves during spraying or laid later by surviving adults do not lead to a high number of mobile ERM later in the season. As a summary of all experiments, it is present- ed that one spray with flubenzimine (150— 250 g. a.i./100 1 water, 300 1/ha) can keep ERM under the economic threshold level if sprayed when the sum of the effective temperature above + 5 °C reaches 200 dd in spring. If tem- perature recordings are made within the or- chard, which is recommended, the sum of 200—250 dd will be accurate enough for tim- ing the spray because of the climatically more favourable situation in the orchards. However, one spring application is not enough to dimin- ish winter egg numbers the next autumn if the weather is suitable for egg laying. High num- bers of overwintering ERM do not always lead to high numbers of mites in the summer rainy weather in the spring may considerably diminish ERM numbers (Putman 1970). Be- sides, ERM winter mortality in Finland may often be quite high, 30—60 % (Listo et al. 1939). One spray with flubenzimine (150 g a.i./100 1 water, 0.45 kg/ha) greatly reduced the num- ber of predatory phytoseiid mites. This reduc- tion cannot be explained by a reduction of prey, because the dominating phytoseiid spe- cies concerned Euseius finlandicus (Oud,), is known to also use other food sources than phytophagous mites, e.g. pollen, and has been 330 found to be quite common on apple leaves also without phytophagous mites as prey (Kropc- zynska and Tuovinen 1988). Another common species was Phytoseius macropilis (Banks). The same effect was obtained also by sprays with lower concentrations of flubenzimine (25 85 g a.i./100 I water) when sprayed 5 times per season. ViGLet al. (1985) also noted the harm- ful effect of flubenzimine to predatory mites. However, Comai (1985) sprayed flubenzimine in an even lower concentration(10 g a.i./100 1 water) and concluded that 6 sprays during the season did not affect coccinellids or a phytoseiid mite Typhlodromus spp. Flubenzimine had no clear harmful effect on predatory insects in orchards. Boness (1983) stated that anthocorid bugs were not badly damaged by flubenzimine in either larval or adult stages. This was found also in the pres- ent study. If no insecticidal sprays are per- formed, anthocorid bugs belong to the most important insect enemies of ERM in Finland (Lisro et al. 1939). However, flubenzimine diminished spider numbers, which occur quite commonly in apple trees not treated with harm- ful insecticides. Because of its harmful effects on predatory mites, at least Euseius Pinlandicus and Phytoseius macropilis, flubenzimine cannot be recom- mended for regular use in integrated control programs in apple orchards. However, because of the lesser effects on predatory insects e.g. anthocorid bugs, the use of flubenzimine may be reasonable also in IPM orchards in situations where quick reduction of ERM is necessary and phytoseiids are scarce. None of the reference products was as effec- tive as flubenzimine. The effect of chinometh- ionate was usually satisfactory and chinometh- ionate controlled even high populations of ERM, at least when applied twice. However, on many occasions, growers have reported an un- sufficient effect by this acaricide. Dicofol was tested in only one experiment. The effect of a single spray was satisfactory, although not as good as that of flubenzimine. The effect of fen- butatinoxide was comparable to that of chino- methionate and dicofol. This acaricide is not ap- proved for ERM control in Finland. Oxydemetonmethyl had a good knock-down effect on ERM when sprayed after winter egg hatching. However, later in the season, an out- break of ERM may occur, and a spray with an acaricide is needed. Because of the risk of residues, oxydemetonmethyl is not recom- mended for use in June or later. Although del- tamethrin had an immediate effect on ERM, later in the season it caused an outbreak of ERM. This effect has been observed in many studies (e.g. Mantingerand Dipoli 1982,Arias and Nie- to 1983). Because of these findings the use of deltamethrinand other pyrethroid insecticides are not recommended for summer sprays in apple orchards. REFERENCES Arias, A. & Nieto, J. 1983. Eficacia de dos piretroides sobre Zeuzera pyrina L. y Laspcyrcsia pomonella L. y efecto secundario frente a Panonychusulmi Koch. Anales del Inst. Nac. Invest, Agr. Agric. 24: 251 —266. Boness, M. 1983. Peropal, Alsystin und Cropotex: Unter- suchungen iiber ihre Wirkung auf Nutzarthropoden. Pfl.schutz-Nachr. Bayer 36: 38—53. Comai, M. 1985. Grado di controllo del ragno rosso eser- citato da nuovi prodotti acaricidi. Informatore Agrario 41: 65—68. Hassan, S. A., Albert, R., Bigler, F., Blaisinger, P., Bogen scHiiTZ, H., Boller, E., Briin, J., Chiverton, P., Ed- wards, P., Englert, W. D., Huang, P., Ingleskield, C., Naton, E., Oomen, P. A., Overmeer, W. P, J., Riec.kmann, W., Samsoe-Petersen, L., Stäiibli, A,, Tuset, J. J., Van wetswinkel, G. & Viggiani, G. 1987. Results of the third joint pesticide testing programme by the lOBC/WPRS- working Group »Pesticides and Beneficial Organisms». J. Appi. Entomol. 103: 92—107. Karo, W., Gottwald, R. & Freier, B. 1987. Die Selektivital 331 von Pflanzenschutzmitteln und ihre Bedeutung. Nachr.bl. Pfl.schutzd. DDR 41; 218—223. Kolise, W. 1981. Untersuchungen zur Bekämpfung der Obstbaumspinnmilbe(Panonychus ulmi) mit den Ent- wicklungshemmern Cropotex und Nikkomycin. Pfl. schutz-Nachr. Bayer 34: 264—301. Kropczynska, D. & Tuovinen, T. 1988, Occurrence of phytoseiid mites (Acari: Phytoseiidae) on apple-trees in Finland. Ann. Agric. Fenn. 27: 305—314. Lees, A. D. 1953. Environmental factors controlling the evocation and termination ofdiapause in the fruit tree red spider mite Metatetranychus ulmi Koch (Acarina: Tetranychidae). Ann. Appi. Biol. 40: 449 —486. Listo, J., Listo, E.-M. & Kanervo, V. 1939. Tutkimuksia hedelmäpuupunkista(Paratetranychuspilosus C. & F ). (Ref: Studies of the fruit tree red mite (Paratetranychus pilosus C. & F ). Valt. Maatal.koetoim. Julk. 99: 1—143. Mantinger, H., Dipoli, P. 1982. Einfluss von syntetischen Pyrethroiden auf die Entwicklung von Spinnmilben Spritzversuch 1981. Obstbau Weinbau 19: 135—137. Putman, W. L. 1970. Effects of water and high humidity on the European red mite, Panonychus ulmi (Acarina: Tetranychidae). Can. Entomol. 102: 955—961. Steel, R. G. D. & Torrie, J. H. 1980. Principles and proce- dures of Statistics. 2nd ed. McGraw-Hill, New York. 633 p. Swiht, F. C. 1968. Population densities of the European red mite and the predaceous mite Typhlodromus (A.) falla- cis on apple foliage following treatment with various insecticides. J. Econ. Entomol. 61: 1489—1491. Tuovinen, T. 1990. Chemical control of European red spider mite Panonychus ulmi (Koch.) 11. Evaluation of clofentezine and hexythiazox. Ann. Agric. Fenn. (In print) Viol, J,, Boscheri, S., Mantinger, H, 1985. Einfluss ver- schiedener Insektizide und Akarizide auf Raubmilben. Obstbau Weinbau 22: 108—112. ZOEBELEIN, G., DÖRNTLEIN, D., HaMMANN, I. & SCHOLL, W. 1979. BAY SLJ 0312, ein Spinnmilben-Entwicklungs- hemmer aus einer neuen Wirkstoffklasse. Mitt. Biol. Bundesanst. Land-Forstwirtsch., Berlin-Dahlem, Heft 191: 283—284. —, Dörntlein, D. & Hammann, I. 1980. Labor- und Frei- landergebnisse mit Cropotex, einem Akarizid aus ein- er neuen Wirkstoffgruppe. Pfl.schutz-Nachr. Bayer 33: 169—184. Manuscript received March 1989 Tuomo Tuovinen Agricultural Research Centre Institute of Plant Protection SF-31600 Jokioinen, Finland SELOSTUS Hedelmäpuupunkin kemiallinen torjunta. I. Flubentsimiini. Tuomo Tuovinen Maatalouden tutkimuskeskus Hedelmäpuupunkintorjunta tuottaa käytännön omenavil- jelyksillä usein enemmän ongelmiakuin muiden tuhoeläin- ten torjunta. Biologisten tai muuten punkkien luontaisille vihollisille haitattomien menetelmien soveltaminen hyön- teisten torjunnassa helpottaisi hedelmäpuupunkinluontaista torjuntaa. Ennen kuin tällaiset menetelmät ovat käytettä- vissä, on punkkien torjunta akarisideilla tarpeen. Tällähetkellä Suomessa on käytettävissä vain kaksi aka- risidia: dikofoli ja kinometionaatti. Lisäksi oksidemetoni- metyyli tehoaa myös punkkeihin. Akarisidien tehokäytän- nössä on osoittautunut vaihtelevaksi, mikä saattaa osittain johtua mahdollisesta resistenssistä runsaasti käytettyjä val- misteita vastaan. Uusia tehokkaita ja luontaisille vihollisil- le mahdollisimman haitattomia akarisideja tarvitaan. Flubentsimiini vaikuttaa kehrääjäpunkkien muodonvaih- dokseen estämällä kitiinisynteesiä. Valmiste tehoaa punkin nuoruusasteisiin, mutta ei tapa aikuisia punkkeja. Suorite- tuissa torjuntakokeissa valmiste osoittautui tehokkaaksi ja yksi ruiskutuskerta((0.40.755 —0.75 kg tehoainetta/ha, sumuruis- ku) ajoitettuna punkkien talvimunien kuoriutumisen lop- puvaiheeseen, riitti pitämään punkkien määrän torjunnan kynnysarvojen alapuolella. Tehoisana lämpösummana (yli + 5 °C) mitaten sopivakäsittelyajankohta on kun 200—250 astetta on saavutettu. Punkkien lisääntymiselle edullisissa oloissa, kuivan ja lämpimän sään vallitessa, toinen ruisku- tus voi olla tarpeen heinäkuussa. Tällöin talvehtimaan jää- vä punkkikanta on pieni ja ruiskutuksen vaikutus tuntuu vielä seuraavanakin vuonna. Maatalouden tutkimuskeskuk- sen tuhoeläinosasto on antanut Maatilahallitukselle myön- teisen lausunnon flubentsimiinin käyttökelpoisuudesta ja tehokkuudesta vuonna 1984. Jatkotutkimuksissa todettiin flubentsimiinin tehoavan hy- vin myös äkämäpunkkeihin, omenalla kellastajapunkkiin. Hedelmäpuupunkin luontaisiin vihollisiin, petopunkkeihin, valmiste vaikutti haitallisesti. Sen sijaan petoluteiden esiin- tymiseen valmiste vaikutti vain vähän. Flubentsimiinia voi- daan käyttää myös integroitua torjuntaa soveltavissa tarhois- sa silloin, kun petopunkkeja ei luontaisesti esiinny. 332 V ANNALES AGRICULTURAE FENNIAE, VOL. 29: 195—204 (1990) Serla ANIMALIA NOCENTIA N. 149 Sarja TUHOELÄIMET n :o 149 CHEMICAL CONTROL OF EUROPEAN RED SPIDER MITE PANONYCHUS ULMI (KOCH) 11. EVALUATION OF CLOFENTEZINE AND HEXYTHIAZOX Tuomo Tuovinen Tuovinen, T. 1990. Chemical controlof European red spider mite Panonychus ulmi (Koch). 11. Evaluation of clofentezine and hexythiazox. Ann. Agric. Fenn. 29: 195—204, (Agric. Res. Centre, Dept. Plant Protect., SF-31600 Jokioinen, Finland.) In laboratory tests, 250 and 500 ppm clofentezine sprayed on winter eggs ofP. ulmi at 0—63 day-degrees (dd) above + 7 °C, had a 68—92 % effect. If sprayed just be- fore the beginning of egg hatching (128 dd above 7 °C), the effect was only 35 %. In field tests, a goodeffect was obtained when clofentezine was sprayed before the beginning of embryonic development of winter eggs. In laboratory tests, 50 and 100 ppm hexythiazox diminished hatching of unde- veloped winter eggs (92 and 99 % effect), but the effect was poor when sprayed after some development of the eggs had occurred (77 dd above 7 °C). In field tests, hexythiazox had a good effect when sprayed in spring during the winter egg hatch- ing period or in July. When sprayed five times on trees with low density populations ofP. ulmi, in coor- dination with the apple scab spraying schedule, clofentezine and hexythiazox sig- nificantly diminished the numbers of phytoseiid mites, but did not totally eliminate them. Single summer treatments with both acaricides were relatively harmless on phytoseiid mites Euseius finlandicus and Phycoseius macropilis. Repeated summer sprays with clofentezine reduced numbers of Aculus sclechtendali, but hexythiazox did not have any effect on eriophyiid mites. Index words: chemical control, acaricides, clofentezine, hexythiazox, European red spider mite, Panonychus ulmi, Eriophyidae, Phytoseiidae, Euseius finlandicus, Phytoseius macropilis. INTRODUCTION The results of the control experiments on the European red spider mite (ERM), Panonychus ulmi (Koch) (Acad: Tetranychidae), using flubenzimine compared to the conventional acaricides chinomethionate and dicofol as well as oxydemetonmethyl, have been published earlier (Tuovinen 1989). Of the other available acaricides, ovicidal oil preparates have been widely used against ERM. Most of the ovicidal acaricides have been tar oil or various petro- leum oil formulations. Sprays on winter eggs, before onset of the vegetation period, result in satisfactory control provided the coverage of the spray is complete and the egg hatching pe- riod short (van de Vrie 1985). In Finland, the hatching of winter eggs lasts several weeks (Listo et al. 1939) and this probably is the rea- son for the often poor effect of mineral oil 195 preparates. The use of tar oils which have a good effect on ERM winter eggs is now pro- hibited in Finland because of the harmful com- pounds in these oils. Recently, two new ovo-larvicidal com- pounds completely different in chemical struc- ture as well as in mode of action compared to earlier acaricides have been introduced: clofentezine, effective primarily against eggs (Bryan et al. 1981, Neal et al. 1986) and hex- ythiazox, effective against the eggs and larvae of tetranychid mites (Welty et al. 1988). These two compounds have been tested in laborato- ry and field experiments in order to evaluate their effectiveness against ERM and their impact on other mite groups in apple trees. In this study, theresults of the above tests are reported and the use of clofentezine and hexythiazox compared to other acaricides is discussed. MATERIAL AND METHODS Clofentezine was used as 50 % WP formulation Apollo, produced by Schering AG, and hex- ythiazox as 10 % WP formulation Nissorun 10 WP, produced by Nippon Soda Co. As reference products, a mineral oil formu- lation (Ovipron, BP), chinomethionate (25 % WP formulation Morestan, Bayer AG), fluben- zimine (50 % WP formulation Cropotex, Bayer AG) and oxydemetonmethyl (26.5 % EC for- mulation Metasystox, Bayer AG) were used. In some of the field experiments, insecticides and fungicides were applied following normal spraying schedules. These sprays were carried out using the recommended concentrations and doses. Laboratory experiments Twigs containing ERM winter eggs were sam- pled from orchards during winter and were stored in 0— + 3 °C before tests. For each test, twigs from the same orchard were used. s—lo5 —10 pieces I—31 —3 cm in length, halved twig bits con- taining 25—50 eggs each were put into petri dishes on filter paper and sprayed with 2 ml of water diluted preparate in a Potter tower. Con- trol dishes were sprayed with pure water. Af- ter spraying, the twig bits were put on petri dishes and each bit circled by insect glue. The dishes were preserved in a growing chamber at + 20/ + 15 °C temperature, 75 ± 10 % Rh and 13/11 h photoperiod (L/D). The dishes were un- covered. Each treatment was replicated four times and control dishes were included. The twig bits were checked two and four weeks af- ter the treatments and the hatched larvae stuck in the insect glue were counted. Clofentezine at 0.025 and 0.05 % a.i. dilu- tions was tested using eggs at various develop- mental stages. Eggs were obtained by preserv- ing twigs in 0 °C, + 5 °C, + 10 °C and + 15 °C for o—2l days. Hexythiazox was tested on un- developed and partly developed eggs using 0.005 and 0.01 % a.i. dilutions. During laboratory experiments in growing chambers, the temperature sums were recorded using a growing degree day accumulator (TASI-P, Omnidata Int. Inc.). As a threshold temperature for winter egg development, + 5 and +7 °C was used (Lees 1953)- Field experiments In a commercial orchard, Paimio 1986—88, clofentezine was compared with chinomethio- nate and flubenzimine in two 0.5 ha blocks. In Piikkiö, 1988, hexythiazox was compared with chinomethionate in a demonstrative test. In both orchards, insecticides against moths and 196 fungicides against the apple scab Venturis in- aequalis (Cooke) Winter were also used. In an experimental orchard, Jokioinen 1988, hexythiazox and clofentezine together with flubenzimine, were tested using fully ran- domized design and six single tree replicates. Preparates were sprayed according to the ap- ple scab spraying schedule usinglower concen- trations in order to check the possible effect of these acaricides on apple scab. As a reference product bitertanol (Baykor, Bayer AG) was sprayed against the apple scab. In an experimental orchard, Pälkäne 1988, summer applications of hexythiazox were studied using randomized block design and three single tree replicates. In 1989, the effect of early sprays of clofentezine, hexythiazox and a mineral oil preparate was studied. In Paimio and Piikkiö the effect of sprays was checked I—4 times during summer by sam- pling 5 leaves of equal size and position from 10—20 randomly selected trees, and in the au- tumn, by sampling five 20 cm twig pieces from 10—20 trees. In Jokioinen , 20 leaves from each tree were sampled in July, and in Pälkäne, 10 leaf-rosettes in spring and 10 leaves during sum- mer from each tree were sampled. Numbers of living mobile mites and ERM eggs were counted under a stereomicroscope. All relevant mite groups, including Tetranychidae, Tydeidae, Phytoseiidae and Eriophyidae, were observed. In some cases, numbers of eriophyids were es- timated using a scale from 0( = no mites) to 3 ( = over 100 mites/leaf). Meteorological data were obtained from the nearest meteorological station (Piikkiö and Pälkäne). Cumulative temperature sums over + 5 °C (day-degrees) were calculated for timing of the sprays. Data from laboratory tests were analysed using the analysis of variance (Tukey’s test) and from the field experiments using either t-test or analysis of variance (Duncan’s multi- ple range test) on log(x+ l)-transformed data (Steel and Torrie 1980). RESULTS Laboratory experiments degrees for +7 °C and 170 dd for +5 °C threshold temperatures (Fig. 1). Half of the eggs were hatched when 170 and 200 dd above + 7 and +5 °C were reached, respectively. The temperature sums needed for the begin- ning of ERM winter egg hatching were 140day- Table 1. Effect of clofentezine on ERM winter eggs at differ- ent stages of egg development. Treatments in Potter tower, 2 ml of dilution/replicate (see text). Preserving dd Effect % (Abbott) (7 °C) temp. (°C) time (d) 250 ppm 500 ppm 0 7 0 87.3" 91.5" 5 14 0 92.2" 90.7" 5 28 0 68.4» 81.0" 10 7 21 77.9" 82.0" 10 14 42 83.4b 92.5" 10 21 63 77.2" 79.8" 15 16 128 37.3' 351' Means with different letters in columns denote significant differences (P<0.05) according to Tukey's test. 197 Fig. I, Hatching of ERM winter eggs in a growing cham- ber in + 20/15 °C, 13/H h photoperiod (L/D) and 75± 10 % Rh. Day-degreesrecorded from the beginning of the test. Regression curve calculated from 19 replicates, 95 % con- fidence intervals are included. Clofentezine affected undeveloped ERM win- ter eggs well (Table 1). As embryonic develop- ment progressed the effect of clofentezine on egg hatching diminished when sprayed I—21 —2 days before hatching. The concentration of 250 ppm was only slightly less effective than the double one. Hexythiazox at 50 and 100 ppm concentra- tionkilled the undeveloped winter eggs almost totally but, like clofentezine, the effect on the more developed eggs was poor (Table 2). Field experiments In 1986, Paimio, clofentezine was sprayed on winter eggs, a few of which had already hatched (9-5., sprayed when 83 day-degrees above +5 °C was reached). The initial ERM winter egg density was high, 199 eggs/10 cm Table 2. Effect (Abbott) of hexythiazox and clofentezine on ERM winter eggs. Exp. 1. was carried out on undevel- oped eggs, Exp. 2. on winter eggs after preserving in + 20/15 °C for 7 days ( = 77 dd above 7 °C). Treatments as in Table 1, Effect % (hatch. %)Treatment (% a.i.) Exp. 2.Exp. 1. Hexythiazox (0.005) 99.3 (0.6a ) 24.4 (70.5 b) Hexythiazox (0.01) 99.4 (0.5 a) 48.9 (47.6s) Clofentezine (0.025) 92.6 (6.2 b) 34.9 (60.7 b) Untreated (84.l c) (93 3°)(84. U) (93.3 C) Means with different letters in columns indicate significant differences (PC0.05) in hatching-% according to Tukey’s test. branch, leading to a high population level on the control block. At first, in June, the effect of clofentezine was satisfactory compared to the control block, but in July and August, an outbreak of ERM occurred (Table 3). A spray Table 3. Results of the field experiment in Paimio, 1986. Blocks of about 0.5 ha were sprayed with a mist sprayer, 3001/ha. Numbers ofmobile mites and eggs were counted from 5 leaves/tree, and numbers ofwinter eggs from 5 twigs/tree from 10 trees/treatment. Before the treatment in spring the number of winter eggs was 199/10 cm twig. Treatment and rate Date No. of ERM/leaf (mobile and eggs) ERM (g a.i./100 1) winter- -295. 19.623.7 16.9 eggs mob mob mob eggs mob eggs Clofentezine (100) 9.5. 8.31.1 294 43.275.1 34.8 219 Chinomethionate (62.5) 4.6. 104.51.9 70.575.8 683 46.0 267 T-test ••• NS NS • NS Other treatments in the area: fenltrothion (375 g a.i./100 I) 20,5. (only clofentezine) and 19.6,, dimethoate (133) 7.7., dithianon (225) 14.5., 23.5., 4.6., 9-6., 19.6., 13 7. and triforine (123 5) 7.7. (for scab control). * PC0.05; * * * P< 0.001 Table 4. Results of the field experiment in Paimio, 1987. Blocks of about 0.5 ha were sprayed with a mist sprayer, 300 1/ha. Numbers of ERM were counted from 5 leaves/tree, and numbers of winter eggs from 5 twigs/tree from 10 trees/treatment. Before the sprays in spring the number of winter eggs was 243/10 cm twig. Treatment and rate Date No. of ERM/leaf (mobile and eggs) ERM (g a.i./100 1) " winter- -22.6. 16.7. 30.7. Erioph. eggs mob mob eggs mob eggs Clofentezine (100) 294.0.04 0.220.32 031 1.3 > 100 —' Flubenzimine (250) 10.6. 0.12 0.33 16 39 0 17.5 T-test NS NS * NS 1 sign indicates missing data. Other treatments in the whole area: dimethoate (133 g a.i./100 1) 3.6. and 22.7., dithianon (250) 18.5., 3-6., 10.6., 14.6., 23.6., 29.6. and 9.7. (for scab control). * P<0.05 198 Table 5. Results of the field experiment in Paimio, 1988, Blocks ofabout 0.5 ha were sprayed with a tractor mist sprayer, 400 1/ha. Numbers of ERM were counted from 100 leaves/treatment and winter eggs from 20 twigs/treatment. Treatment and rate Date No. of ERM/leaf (mobile and eggs) (g a.i./100 1) ; ;15.6. 30.6. Erioph. 10.8. mob eggs mob eggs mob eggs Hexythiazox (15.0)+ 195.+ 0.040.4 1.02.2 71.10.0 0.0 chinomethionate (62.5) 4.7., 14.7. Chinomethionate (62.5) 20.5., 4.7., 0.037.2 137 38.140.6 0.00.3 14.7. T-test NS '•* •'• •" ** NS Other treatments in whole area: dimcthoate (133 g a.i./100 1) 20.—23.5-, 4.7. and 14.7., dithianon (250) 23.5., 2.6., 9.6. and 21.6., bitertanol (100) 27.6. (for scab control). ** P