The phytotoxicity of disinfectants and their effect at different temperatures Hanna Avikainen, Hilkka Koponen, Beata Meinander and Risto Tahvonen Avikainen, H., Koponen, H., Meinander, B, & Tahvonen, R. 1993. The phytotoxicity of disinfectants and their effect at different temperatures. Agric. Sei. Finl. 2: 161-168. (Agric. Res. Centre of Finland, Inst. PI. Prot., FIN-31600, Jokioinen, Finland and Dept. Plant Biology, P.0.80x 28, FIN-00014 Univ. Helsinki, Finland.) When disinfecting plastic growth containers, only sodium hypochloride (NaCIO) caused damage both to cucumber and lettuce seedlings grown on peat if the containers had not been washed with water after disinfection. Also the seedlings grown on rockwool cubes were susceptible to Menno-Ter-forte when the growthcontainers were not properly rinsed after disinfection. All tested disinfectants caused damage to cucum- ber, lettuce and cauliflower seedlings when mixed in the peat substrate. The efficiency of disinfectants was higher at +2O°C than at +5°C, especially against Fusarium culmorum, F. oxysporum and Rhizoctonia solani. A decrease in temperature affected least the efficacy of NaOCl and Menno-Ter-forte and most that of Virkon S. Key words: cauliflower, cucumber, disinfection, lettuce Introduction With increasing and rationalisation of greenhouse cultivation better hygiene in greenhouses is re- quired than previously. With expanding horticul- tural markets the risk of spread of plant pathogens has increased. Previously, disinfection of green- houses consisted mainly of disinfection of the sub- strate (Linnasalmi 1955). Disinfection of soil has, however, become unnecessary as the growth sub- strate is changed after each growing period and it is used in plastic containers.Disinfection ofstructures and equipment still is important, because many plant pathogens may survive long in plant debris and in soil particles. There are several disinfectants on the market. Many of them have been developed for use in do- mestic animal farms and food production, not actu- ally for disinfection of greenhouses. The disinfect- ants for use in greenhouses must be effective against plant pathogens and harmless to the plants. There is little information about the phytotoxicity of disinfectants. Formaldehyde fumes at high tem- peratures and causes damage to flowers and plants (Straetmans 1984). This has been observed in greenhouses when the temperature has been in- creased after disinfection. Formaline residues in the substrate have caused damage to cabbage seedlings (Linnasalmi 1952,1955). Thorough cleaning of greenhouses and storages is recommended in autumn, at the end of the grow- ing season when the greenhouse is emptied, and the temperature is decreased. The best disinfection re- sult is, however, obtained in conditions favourable to the growth of microbes (+2O-30°C, humidity 70-90 %) (Engvall 1988). The optimum temper- 161 Agric. Sei. Fint. 2 (1993) https://www.c-info.fi/en/info/?token=LvJLv7MGbAXhqByq.esrz5BeBxtOiYgoyQOHTYQ.Mi7CBg5R8TieUTCBDy74E2WYUiGKWgL1hKCWgwj3JOLDRI3v1W_UUiQZUtLjiCZtc3ajHxxboIqjGU9KWDhNQFOfK62liPso8eNLHBQSjNXGDjLIgsPnnnJRXc3D9aFbLvO35MetELkp5l8wiLpUpeh0Q9Kl7nSD-Si1NPOH9GAFiSNVwuiaGsHwwA8nCYO_HQbCqGOvRp8L5PqWr3BSlOOi6kST2GhRqKFd3mZMUqFHWenIFbxxkzUjysMGHWvEtP1f9xybdllqhLPb30DOoRGCbyVdcmblU4I8Tuetd4cVpB4umBDWz_wVpeFCTT14fjzerBUiuztr4g ature for a number of disinfectants is approx. +2O°C. Formaline, for instance, is inactivated at below +ls°C (Åkesson 1990). The aim of the present study was to determine the phytotoxicity of disinfectants as well as their effi- cacy at different temperatures. The study was car- ried out in 1988-1990 at the Institute of Plant Pro- tection of the Agricultural Research Centre. Material and methods Disinfectants The phytotoxicity of seven disinfectants (Table 1) was studied on seedlings of cucumber, lettuce and cauliflower and the effect of disinfectants on nine fungi at different temperatures. Formaline was in- cluded only in the temperature trials. The concen- trations recommended by the manufacturers were used. The dilutions were made in distilled water for the laboratory trials and in tap water for the green- house trials. Table 1. The disinfectants, their active ingredients and con- centrations recommended by the manufacturers. Disinfectant Active ingredient, % Recom- mended concentra- tion, % Formaline Formaldehyde, 37 5.0 lobac P lodine, 1.83.0 Ipasept Quaternary ammonium compounds, 2.82.0 Korsolin Glutaraldehyde, 10 1.0 Menno-Ter-forte Quaternary ammonium compounds, 32.81.0 Sanisept Quaternary ammonium compounds, 2.52.0 Sodium hypochlorite Active chlorine, 10 10.0 (NaOCl) Virkon S Potassium peroxysul- phate,6o 1.0 Phytotoxicity of disinfectants In the phytotoxity trials, cucumber variety ’Dale- va’, lettuce varieties ’Cortina’ and ’Grand Rapids’ and cauliflower variety ’Tanskalainen suuri’ were used as test plants. The growth temperature was +lB-20°C for lettuce and cauliflower and +22-25°C for cucumber. Additional light of 6000 lux was given to the seedlings. The growth peat was fertil- ized with 150 g peat compound fertilizer and 800 g Dolomite lime/1001 peat. Disinfection of plastic pots The phytotoxicity ofdisinfection ofplastic growth containers (Vefi) and plastic pots (1 dl) was tested on lettuce and cucumber. Peat was used as the growing medium. The containers were soaked in a disinfection suspension for four hours and the pots for three hours. Half of the NaOCl treatedpots were washed under running water. The pots immersed in other disinfectants were not washed. On the day after disinfection lettuce seeds were sown in the containers and cucumber seeds in the pots. The lettuce trial consisted of three replicates with 32 seeds, and the cucumber trial of five replicates with two seeds per replicate. The condition of seedlings was checked three weeks after sowing. The plants were evaluated visually on a rating scale of0-3:0 = no damage, 1 = slight damage, growth suppressed, 2 = clear damage, growth clearly suppressed and 3 = severe damage, plant and roots dead. The fresh weight of the seedlings was also recorded. Analysis ofvariance was used in the statistical analysis of the results, and significances were tested with Dunnet’s test. The effect of Menno-Ter-forte on plants grown on rockwool was studied in the following experi- ment. Plastic boxes (50 x 25 x 9.5 cm) were soaked for 60 min in 1 % Menno-Ter-forte solution. Half of the boxes were washed underrunning water. The boxes were allowed to dry for four hours. Thereaf- ter rockwool and peat cubes (4x4x4 cm) were placed into the disinfected boxes. The test plants were cucumber and lettuce. Before sowing the rockwool cubes were soaked wet in 0.05 % fertil- izer solution containing hydrofertilizer and lime salpeter (2:1). The cucumber trial consisted of four replicates with 15 plants and the lettuce trial of three replicates with 25 plants. The treatments 162 Agric. Sd. Fin!. 2 (1993) were: no disinfection, disinfection with no washing and disinfection with washing. The cucumber trial lasted 10days and the lettuce trial three weeks after sowing. At the end of the trial the height and fresh weight of seedlings were measured and the damage caused to the plants was evaluated on a rating scale of 0-2: o=no damage, l=slight damage, 2=leaves dark green, growth stopped or dead seedling. The growth index was determined with the formula: Growth index = (a+b): (c+d) x 100 a = height of seedlings, cm b = fresh weight of seedlings, g c = height of seedlings on non-disinfected rock- wool d = fresh weight of seedlings on non-disinfected rockwool In the rockwool trials the results were analysed with the split-plot analysis ofvariance and signific- ances were tested with Tukey’s test. Phytotoxicity of disinfectants mixed in peat The phytotoxicity of the disinfectants in peat was studied on lettuce, cucumber and cauliflower. The disinfectant was mixed 0,0.01,0.1,0.5,1.0,2.0and 5.0 ml or g per 1 1 peat. In addition, the substrate of cauliflower was treated by 2.5 ml or g. The disin- fectant was diluted in 125 ml of water which was mixed in 1 I of peat. The peat was divided into pots where the seeds were sown or the seedlings planted. The seeds were covered with untreated peat. One-week-old cucumber seedlings were planted into 0.5 1 pots. The trial was made with five repli- cates and two seedlings per replicate. Three weeks after planting the height and fresh weight of seed- lings were recorded and the condition ofshoots and roots was evaluated visually on a rating scale of 0-3: o=no damage, l=slight damage, growth sup- pressed, 2=evident damage, growth inhibited, 3=growth stopped, dead plant. The lettuce trial was made with three replicates and 32 seedlings per replicate. Three and four weeks after sowing the degree of infection was determined randomly on 15 plants on a rating scale of0-3 as in the cucumber trial. The fresh weight of the seedlings was also recorded. In the cauliflower trial there were four replicates and 36 seeds per replicate. The height of the seed- lings was recorded two weeks after sowing. At the end of the trial (three weeks after sowing) the fresh weight of plants was recorded and the damage was evaluated on a rating scale of 0-3 as in the cucum- ber trial. Analysis of variance was used in the statistical analysis of the results. Significances were tested with Dunnet’s test. A phytotoxicity limit was de- fined as the lowest concentration of disinfectant mixed in peat causing clear damage to plants or reduction in the height, or the fresh weight was determined for each disinfectant. The effect of temperature on the disinfection efficiency Nine fungi were included in the temperature study (Table 2). The names of the fungi are mainly ac- cording to Domsch et al. (1980). The fungal iso- lates were obtained from the collections of the In- stitute of Plant Protection of the Agricultural Re- Table 2. The fungi and the growth media used in temperature tests. Fungus Growth medium Botrytis cinerea Corn meal agar (Difco) + KM) ppm streptomycin sulphate Didymella bryoniae Corn meal agar (Difco) + 100 ppm streptomycin sulphate Fusarium culmorum, Nash and Snyder PCNB medium F. oxysporum Mycocentrospora Corn meal agar (Difco) + 100 ppm acerina streptomycin sulphate Phoma foveata Malt extract agar (Difco), Corn meal agar (Difco) + 100 ppm streptomycin sulphate Pythium sp. Martin's medium Rhizoctorua solani Rhizoctonia agar (Ko and Hora 1971) Verticillium dahliae Corn meal agar (Difco) + 100 ppm streptomycin sulphate 163 Agric. Sei. Finl. 2 (1993) search Centre. In the trial the fungi were isolated and cultivated on different growth media depend- ing on the fungus species (Table 2). The formulas for media are presented in Booth (1971). The choice of temperatures, +5°C, +lo° and +2O°C, was based on previous experience. Before the test all solutions, pots and equipment were kept for 12hours in these temperatures. Plastic pots were scratched with sandpaper and contaminated with fungus-peat suspension. The inoculate used was obtainedby mixing one plate of fungus (Fusarium culmorum, F. oxysporum, Mycocentrospora ace- rina, Phoma foveata, Pythium sp., Rhizoctonia so- lani and Verticillium dahliae) and 100 ml sterile water in one litre ofpeat, or by mixing five crushed pieces (4 cm long) of infected (Botrytis cinerea and Didymella bryoniae) plant and 100ml sterile water in one litre of peat. Contaminated plastic pots were dried for 1-2 days. Pieces (4x6 cm) of the pots were immersed in disinfectant for 60 min and rinsed with water. Pieces (0 0,5 cm) of plastic pots were placed on different agar plates (4 pieces plate) depending on the testfungus (Table 2) to determine the susceptib- ility of the fungi to the disinfectant. The plates were kept at +2O °C. The trial consisted of threereplicat- es with three plates. The experiment was repeated twice for lobac P, Menno-Ter-forte, NaOCI and Virkon S. Water was used in the control treatment. The results of temperature trials were calculated as efficiency percentages, i.e. as the proportion of healthy pieces of all pieces. Results Phytotoxicity of disinfectants Of the eight disinfectants tested, only NaOCI caused visible damage both to lettuce and cucum- ber seedlings when the plastic growth containers and pots had been disinfected and seedlings were grown on peat. Damage was observed on the leaf margins, the seedlings were clearly shorter and their fresh weight lower compared to the controls and other treatments (Figs. 1-2). NaOCI treatment caused damage also to the cucumber roots. Rinsing with water eliminated the phytotoxicity of NaOCI. Disinfection of the plastic boxes with Menno- Ter-forte caused clear symptoms in cucumber seed- lings grown on rockwool. The seedlings remained short and they were dark green compared to the control. Rinsing the boxes with water did not re- move the disinfectant totally; some damage was still observed in the seedlings. Disinfection did not damage seedlings grown in peat; their vigour even increased (Table 3). Fig. 1.The effect of disinfection of plastic growthcontainers on the fresh weight of lettuce seedlings grown on peat sub- strate. F=4.41, po.ol compared to untreated peat. Disinfectant Cucumber Lettuce Cauliflower Visible damage Height Weight Weight Heigth Weight Phytotoxicity limit ml or g /l 1 peat lobacP, ml 0.50.5 0.50.5 0.10.5 Ipasept, ml * * * 5.05.0 * Korsolin,ml 5.05.0 5.02.5 2.55.0 Menno-Ter-forte, ml 1.01.0 0.11.0 1.01.0 NaOCl.ml 0.50.5 0.10.5 0.10.5 Sanisept, ml 5.05.0 5.0 * 5.05.0 VirkonS.g 5.05.0 2.01.0 1.02.0 * no phytotoxicity Disinfection of plastic boxes with Menno-Ter- forte decreased also the fresh weight and the height of lettuce grown also on rockwool. Rinsing with water eliminated the phytotoxicity completely. Let- tuces grown on peat were not damaged by disinfec- tion at all (Table 3). NaOCl mixed in peat caused chlorocity and greyish brown spots on the leaves of cucumber, lettuce and cauliflower seedlings, growth stopped and the plants died. The phytotoxicity limit, 0.1 ml, caused slight damage to lettuce and cauliflower. Half a millilitre of NaOCl damaged clearly cucum- ber and cauliflower; the growth of lettuce stopped totally. More than 1 ml caused damage to cucumber roots. Five millilitres killed all test plants (Table 4). lobac P mixed in peat caused dark brown spots on the leaves and stunted growth in all test plants. The lowest amount of lobac P that caused slight damage to lettuce and cucumber and clear damage to cauliflower was 0.5 ml. More than 2.5 ml inhib- ited the development of the plants. The phytotoxic- ity limit of lobac P was 0.5 ml/1 1 peat (Table 4). In the Menno-Ter-forte treatment of peat, the leaves of all test plats were dark green and the plants stunted compared to the controls. One week after the treatment all amounts of the disinfectant caused slight damage to the cucumber seedlings, but the damage disappeared later. The phytotoxic- 165 Agric. Sei. Finl. 2 (1993) Table 5. The effect of temperature (+5, +lO ja +2O °C) on the disinfection efficiency against fungi on plastic surfaces. Disinfection time 60 min. Fungus Disinfectant Water Formaline lobac P Ipasept Korsolin Menno- NaOCl Virkon S Ter-forte Minimum working temperature °C/efficiency % Botrytis cinerea 20/28 5/100 5/100 5/100 10/100 5/100 5/100 10/100 Didymella bryoniae 20/11 5/100 5/100 5/100 5/100 5/100 5/100 5/100 Fusarium culmorum 20/18 20/100 5/100 20/58 20/100 10/100 5/100 20/89 Fusarium oxysporum 20/4 20/75 20/100 20/92 20/83 10/99 5/100 20/95 Mycocentrospora acerina 20/31 20/100 5/103 5/100 5/100 5/100 Phomafoveata 20/27 20/67 5/103 5/100 5/100 5/100 5/100 20/100 Pylhiumsp. 20/56 5/100 5/103 10/92 20/100 20/100 5/100 20/100 Rhizoctonia solani 20/17 20/100 10/103 10/100 20/58 20/100 5/100 20/100 Verticillium dahliae 20/46 5/100 10/103 - - 20/99 5/100 20/96 ity limit of Menno-Ter-forte was 1 ml/1 1 peat, which caused damage to the cucumber roots, let- tuce and cauliflower(Table 4). One gram of Virkon S mixed in peat caused slight damage to cauliflower. Two grams clearly disturbed the growth ofcauliflower, cucumber and lettuce. Five grams of Virkon S inhibited the growth of all test plants. The phytotoxicity limit was 2 g/1 1 peat (Table 4). The phytotoxicity limit ofKorsolin was 2.5 ml/1 1 peat. This quantity caused slight growth disturb- ances to cauliflower, and 5 ml caused clear symp- toms in lettuce and cucumber. The phytotoxicity limit of Sanisept was 5 ml/1 1 peat. Ipasept was the least phytotoxic of the disinfectants studied. In cu- cumber and lettuce it caused no damage and 5 ml caused slight damage to cauliflower (Table 4). The effect of temperature on the efficiency of disinfectants At +5°C, NaOCl maintained best its efficiency against all fungi. Also lobac P and Menno-Ter-forte were rather effective in this temperature. Formaline was effective at +5 °C against Botrytis cinerea, Didymella bryoniae, Pythium sp. and Verticillium dahliae. The efficiency of Virkon S increased clearly at +2O °C. Korsolin and Ipasept were weak at all temperatures. In the control ofFusarium cul- morum, F. oxysporum and R. solani the disinfect- ants were most effective at +2O °C. For eradication of B. cinerea, D. bryoniae and Phoma foveata, temperatures of +5 °C and +lO °C were sufficient for lobac P, Menno-Ter-forte or NaOCl (Table 5). Discussion NaOCl and lobac P mixed in peat were the most phytotoxic disinfectants. Clear damage was ob- served in lettuce, cucumber and cauliflower when 0.5 ml of either preparation was mixed in peat. In addition, NaOCl was the only preparation which caused damage to cucumber and lettuce seedlings grown on peat if thegrowth containers had not been rinsed with water after disinfection. In previous studies, NaOCl has not been reported to cause dam- age to lettuce and cress (BÖHMER 1983, 1985). When mixed in peat, Menno-Ter-forte 1 ml/1 1 peat caused damage to the test plants. Clear damage was observed in cucumber and lettuce seedlings grown on rockwool cubes if the growth container had not been thoroughly washed with water after disinfection with Menno-Ter-forte. According to Åkesson(1990), too, all surfaces getting in contact with the plants shouldbe washed after Menno-Ter- forte treatment. Böhmer (1983) reported Menno- Ter to cause spots in lettuce seedlings and to de- crease the formation of primary roots in cress. Ac- 166 Agric. Sd. Fint. 2 (1993) cording to JOHANSSON (1985), Menno-Ter Special and Korsolin caused slight damage to pelargonias and begonias. There is evidence of the phytotoxicity of forma- line and disinfectants containing formaldehyde on Saintpaulia ionatha leaf cuttings (Wohanka and Doll 1985), pelargonias and begonias (Johans- son 1985), as well as on cress, lettuce (BÖHMER 1983, 1985) and cabbage seedlings (Linnasalmi 1952). Formaline was not included in the present phytotoxicity studies, but there is evidence of the phytotoxicity of formaline on rape seedlings in other trials (Meinander 1991). In the present study, small seedlings were used in the phytotoxicity tests. The seedlings could revive from the damage caused by some disinfectants (e.g. Menno-Ter-forte) in a couple of weeks. The trials should, however, have been continued longer to confirm the revival. The effect of temperature, light and humidity on the phytotoxicity was not studied. When using disinfectants, careful washing after disinfection is essential, especially when using syn- thetic media and water cultures. For most disinfectants, the optimum disinfection temperature is +l5-20°C (Sundheim 1991). Low temperatures require longer exposure times and higher concentrations than higher temperatures (Baandrup 1984). For formaldehyde (formaline), the optimum temperature is approx. +2O°C. Form- aldehyde is inactivated at below +l5°C (Åkesson 1990, Bång 1987a, b, Sundheim 1991). Bång (1987b) observed formaline to be active against Phoma foveata and Fusarium solani even in the gaseous form at a temperature as low as +lO°C. In the present trials, formaline was effective against Botrytis cinerea, Didymella hryoniae, Pythium sp. and Verticillium dahliae after 60 min also at +5°C. Against other fungi formaline affected best at +2O°C. NaOCl was the most effective of the tested disin- fectants at +5°C, but also lobac P and Menno-Ter- forte were effective. According to Åkesson (1990), Menno-Ter-forte was the most effective at over +l9°C, but the preparation performed well also at +5°C. Glutaraldehyde containing prepara- tions (Korsolin, Glu-cid) can be used at temperat- ures as low as +5°C (ÅKESSON 1990, Engvall 1988). In the present study, Korsolin (1 %) was most effective at +2O°C. The recommended con- centrations for Korsolin are 1 % at over+lB°C, 2 % at +lO-18°C and 3 % at below +lO°C (Åkesson 1990,Baandrup 1984). The efficacy of Virkon S increased at higher temperatures. The weak efficiency of the prepara- tion at low temperatures is partly due to the powder being poorly soluble in cold water. Therefore Virkon S should be mixed in lukewarm water. Dis- infection should be done at temperatures higher than +l5°C. According to the present trials, below + 10°C it is possible to use against Botrytis cinerea, Didymella hryoniae, Mycocentrospora acerina and Phomafoveata NaOCl, Menno-Ter-forteand lobac P compounds. References Åkesson, I. 1990. Sanering och hygien i växthus. Sveriges Lantbruksuniversitet. Faktablad om växtskydd. Trädgård 4T. Baandrup, M. 1984. Desinfektion af undervandingsmåtter. Gartner Tidende 10: 285-287. BAng, U. 1987a. Försök med desinfektionsmedel. Spor pota- tisodl. 5 (2): 32-34. 1987b. Redovisning av försök med desinfektioin genom dimning i konstantrum vid Röbäcksdalen i september 1986. Mimeogr. Böhmer, B. 1983. Untersuchungen zum Einsatz von Desin- fektionsmitteln im Zierpflanzenbau. Gesunde Pfl. 35: 189-197. 1985. Nicht alle Mittel wirken unter Schmutzbelastung. Gärtnerbör. und Gartenw. 85: 836-838. Booth, C. 1971. Methods in microbiology. Academic Press. London. Vol. 4. 795 p. Domsch.K. H., Gams.W. & Anderson,T.-H. 1980. Compen- dium of soil fungi. Academic Press. London. Vol. 1.859 P- Enovall,A., Sjölander, A. & Olsson, S.-O. 1988.Desinfek- tionsmedel vid djurhållning. Svensk husdjursskötsel. Meddelande 154.Eskilstuna. 21 p. Johansson, A.-K. 1985. Löpande desinfektion i växthus av Xanthomonas pelargonii och X. begoniae. Disinfection in greenhouses ofXanthomonas pelargonii and X. bego- niae. Institutionen för växt- och skogsskydd. (Sveriges Lantbr. Univ). Examensarbeten 1985(5). Uppsala. 67 p. 167 Agric. Sei. Finl. 2 (1993) Ko, W.-H. and Hora,F. K., 1971. A selective medium for quantitative determination of Rhizoclonia solani in soil. Phytopathology 61: 707-710. Linnasalmi,A. 1952.Damping-offon herbaceous vegetables and ornamental plants grown under glass in Finland. Ann. Bot. Soc. ‘Vanamo’ 26, (1); 1-120. 1955. Maan desinfiointi. Puutarhaviljelijäin liiton jul kaisuja N:o 111, Helsinki. 46 p. Meinander, B. 1991. Desinfektionsmedels fytotoxiska verkan vid användning i växthus. Institutionen för trädgärdsvetenskap. University of Helsinki. Helsinki. 82 P- Straetmans, U. 1984. Abbaureaktionen von Desinfek- tionsmitteln. Champignon 24 (272): 17-26. Sondheim. L. 1991. Reingering og desinfeksjon mot sjukdo- mar i veksthus. Plantevem i veksthus. Etterutdan- ninngskurs arrangert av statens fagtjeneste for land- bruket. Mimeogr. 5 p. Wohanka, W. & Doll, W. 1985. Was leisten Desinfek- tionsmittel in der Praxis? Deut. Gartenb. 31: 1482-1483. Manuscriptreceived July 1992 Hanna Avikainen Risto Tahvonen AgriculturalResearch Centre of Finland Institute ofPlant Protection FIN-31600 Jokioinen,Finland Hilkka Koponen Beata Meinander Department of Plant Biology P.0.80x 28 FIN-00014 University of Helsinki, Finland SELOSTUS Desinfiointiaineiden fytotoksisuus ja tehokkuus eri lämpötiloissa Hanna Avikainen, HilkkaKotonen, Beata Meinander ja Risto Tahvonen Maatalouden tutkimuskeskus ja Helsingin yliopisto Maatalouden tutkimuskeskuksen kasvinsuojelulaitoksella sel- vitettiin seitsemän desinfiointiaineen fytotoksisuutta kurkun, salaatin ja kukkakaalin taimiin. Tutkittavat valmisteet olivat lobac P (jodi), Ipasept, Menno-Ter-forte ja Sanisept (kvartaa- risia ammoniumyhdisteitä), Korsolin (glutaraldehydi), natrium- hypokloridi (aktiivinen kloori) ja Viikon S (kaliumperoksisul- faatti). Desinfioitaessa muovisia kasvatuskennoja jaruukkuja nat- riumhypokloriitti vioitti sekä kurkun että salaatin taimia tur- veviljelyssä, ellei astioita huuhdeltu vedellä desinfioinnin jäl- keen. Muillavalmisteilla ei vioitusta havaittu. Myös kivivilla- kuutioissa kasvatetut kurkun ja salaatin taimet olivat herkkiä desinfiointiaineille, kun kasvulaatikoita ei huuhdeltu hyvin desinfioinnin jälkeen. Sensijaan turpeessa kasvatetuissa testi- kasveissa vioituksia ei todettu. Koe osoitti, että desinfioinnin jälkeen huolellinen huuhtelu on erityisen tarpeen, kun käyte- tään synteettisiä alustoja ja vesiviljelyä. Natriumhypokloriitti, lobac P, Menno-Ter-forte, Korsolin, Virkon S ja Sanisept aiheuttivat turpeeseen sekoitettuina vioi- tuksia kurkun, salaatin jakukkakaalin taimiin. Desinfiointiaineiden tehokkuutta eri lämpötiloissa (+5 °C, + 10 °C ja +2O °C) testattiin laboratoriossa seuraaviin sieniin: Botrytis cinerea, Didymella bryoniae, Fusarium culmorum, F. oxysporum, Mycocentrospora acerina, Phoma foveata, Pythium sp., Rhizoclonia solani ja Verticillium dahliae. Ko- keissa oli mukana fytotoksisuuskokeissa olleiden valmistei- den lisäksi formaliini (formaldehydi). Valmisteista käytettiin suositeltuja käyttöväkevyyksiä. Desinfiointiaineiden teho oli parempi +2O °C:ssa, kuin +5 °C:ssa, erityisesti Fusarium- jaRhizoclonia-sieniin. Läm- pötilan aleneminen vaikutti vähiten NaOChn, lobac P;n ja Menno-Ter-forten tehoon ja eniten Virkon S:n tehoon. Tehtyjen kokeiden jakitjallisuuden perusteella suositellaan desinfiointilämpötilaksi yli +l5 °C. Jos joudutaan desinfioi- maan alle +lO °C;n lämpötiloissa, voidaan käyttää NaOCl-, lobac P- jaMenno-Ter-forte- valmisteita torjuttaessa Botrytis-, Didymella-, Mycocentrospora jaPhoma- sieniä. 168 Agric. Sd. Pint. 2(1993)