JOURNAL OF THE SCIENTIFIC AGRICULTURAL SOCIETY OF FINLAND 218 Maataloustieteellinen aikakauskirja Voi. 47: 218—244, 1975 Occurrence of Septoria species on cereals in Finland in 1971—1973 Kaiho Mäkelä Department of Plant Pathology, University of Helsinki, Viikki, Helsinki 71, Finland Abstract. This study was carried out on Septoria species found on cereals: spring and winter wheat (Triticum aestivum L.), spring barley (Hordeum vulgare L.), winter rye (Secale cereale L.) and oats (Avena sutiva L.). The objective was to ascertain their distribution and general significance in Finland. The results were obtained from samples of cereals gathered in 2 040 fields all over the country during the growing season 1971 1973. The fungi in all the samples were examined by microscope and cultures and inocula- tion tests were used as well in laboratory. One of the Septoria specieswas found to occur on all the cereals, being most commonly on wheat and two-rowed barley, moderately common on winter rye, very rare on six- rowed barley and only sporadic on oats. Septoria species were observed to occur most commonly in the southwestern and southern parts of the country, whereas they were very rare in the middle parts of the country and Ostrobothnia. The imperfect stages of the fungi (Septoria) occurred dominantly, whereas at all times the perfect stages (Leptosphaeria) were found only occasionally. The following Septoria species were found to occur on cereals: Septoria nodorum (Berk.) Berk. & Br. was found to occur as the most common species on spring and winter wheat and was moderately common on two-rowed barley. The fungus was found on wheat in 60 —7O per cent, and on barley, in about 40 per cent of the localities and for both cereals in 1/3 of the fields that were studied. On the other hand the fungus was found to be very rare on six-rowed barley and winter rye in 6 10 per cent of the localities and only 2—4 per cent of the fields studied. Also in the inoculation tests it was found that S. nodorum isolates, which originated from different cereals, infected not only their own host but all the other cereals with the exception of oats. The perfect stage, Leptosphaeria nodorum Muller was found only a few times on spring wheat, spring barley and winter rye. Septoria avenue Frank f. sp. triticea T. Johanson was found to be the most common on two-rowed barley in about 45 per cent of the localities and in about 1/3 of the fields studied; on wheat in about 35—40 per cent of the localities and in nearly 1/4 of the fields studied. The perfect stage of the fungus, Leptosphaeria avenaria Weber f. sp. triticea T. Johnson was found only a few times on spring wheat and barley. S. avenue Frank f. sp. avenue Shaw was found to occur only occasionally on oats in nearly 10 per cent of the localities and only in 3 per cent of the fields studied. The perfect stage of the fungus, L. avenaria Weber f. sp. avenaria Shaw was found a few times also on oats. https://www.c-info.fi/en/info/?token=ymufNMLkkZOAdTuZ.nVEHITDOr2ojy74YOcp4Bg.HOtI4ezKqVr9n6RI2OrHliOWPwcZaipk7BD_WCCZE1lvjXOdfu5UTAiDWk9pTEdqa0xzvfYiCoYNMeICw-3WZurz6jrJkpzVuiMivmZldKSGLlCyjruVmFCuwFdOVF7vzd0Pbt03oSJJGqlItGKhE-R1QcaOO0IdIVnvCrR-D8kF-tKy % Septoria tritici. Rob. ex Desm. was found to occur only on winter wheat in about 1/2 of the localities and in about 40 per cent of the fields studied. The fungus was found only in the spring (May to early June). It sometimes attacked fields in great profusion. In the inoculation tests it was found that the S. triticis' isolate originated from rye weakly infected not only rye but also spring wheat and winter rye. Septoria secalis Prill. & Delacr. was found to occur only on winter rye, being mod- erately common in 1/2 of the localities and in about 1/4 of the fields studied. On the basis of this study not much can be said about the magnitude or economic importance of the damages caused by the Septoria species. In addition to Septoria species, several other parasitic fungi such as Helminthosporium-, Puccinia-, Fusarium- species and Erysiphe graminis DC. were observed to grow at the same time on the leaves of cereals. Introduction Several Septoria species are known to be serious causers of leaf spot diseases on cereals cultivated all over the world (Sprague 1950). Particularly S.nodorum (Berk.) Berk. & Br. has been found to cause large yield loss (Block 1959, Brönni- mann 1968). On the other hand little is known of the occurrence and effect of several other Septoria species on cereals in many countries. In Scandinavia Septoria species have also been known since the last century (cf. Frandsen 1943, Jorstad 1967), but their significance has remained rather obscure (Leijerstam 1962, Kolk 1966, Hansen and Magnus 1969). In recent years, however, growing attention has begun to be attracted to Septoria species on cereals in Norway (Hansen and Magnus 1969), Denmark (Smedegärd Petersen 1974) and particularly in Britain (Hewett 1965, Holmes and Colhoun 1970, Richardson and Noble 1970, Richardson 1972, Williams and Jones 1972). In Finland Septoria species has been rather insignificant to date. In recent years they have been found to be uncommon on barley and grasses (Mäkelä 1972 a, 1972 b). This study is part of a research project dealing with spot diseases on cereals and specifically with the pathogens causing these diseases (cf. Mäkelä 1972 b, 1974, 1975). The purpose of the present study is to clarify the occurrence of Septoria species on cereals. The study is based on samples of cereals which were gathered in farmers’ fields throughout the country over a three year period (1971-1973). Materials and Methods The bulk of the cereals samples (Table 1) was gathered at a growth stage when the grain was milky ripe, chiefly from late July to early August. The samples of winter wheat and rye were gathered in May also. The leaves were checked for diseases by occular examination on the basis of symptoms. Septoria and Leptosphaeria species were determined in the fol- lowing way: 1. Diseased leaves were kept on moist blotter paper in Petri dishes for a few days, after which the pycnidia and conidia that had grown were examined with a stereomicroscope. 2. Identification of these fungi is not possible by the above procedure alone, therefore microscope slides were 6 219 Jk Table 1. Frequency of Septoria species as a per cent of samples of cereals gathered in various localities and fields in 1971 1973. The samples Septoria species, % of the cereals researched researched in the fields (F) and localities (L) No. ol localities No. of fields S. avenae f. sp. avenae S. avenae f. sp. triticea S. nodorum S. secalis S. tritici Septoria spp. Hor-b Cereals Year FFFFF FFL Oats 1971 50 73 3 1972 142 233 3 1973 48 109 6 1971- 181 415 3 Spring barley .. 1971 69 157 Two-rowed 25 39 Six-rowed 58 117 Spring barley 1972 135 348 Two-rowed 47 59 Six-rowed 113 289 Spring barley 1973 124 299 - Two-rowed 23 52 Six-rowed 112 247 Spring barley 1971 —73 251 803 Two-rowed 83 150 Six-rowed 234 653 Spring wheat 1972 88 140 1973 62 82 - 1972- 111 222 - Winter wheat 1972 62 112 - 1973 56 147 - 1972-73 93 259 - Winter rye 1972 90 201 1973 62 140 - 1972-73 112 341 - - - - - O 3 20 - - - - 0 3 14 - - - - 6 11 19 1 5 10 13 3 - - - 19 36 21 8 - - - 23 36 10 1 - - - 18 33 16 8 - - 5 26 57 34 29 - - 14 63 68 13 3 - - 4 19 40 14 8 - - 5 28 42 29 40 8 83 85 11 1 - - 4 17 29 15 7 - - 4 26 38 29 27 8 59 90 12 2 - - 3 18 41 25 39 - - 1 60 75 18 33 - - 9 56 50 23 37 - - 5 59 72 22 27 - 17 4 52 63 8 33 - 54 3 60 75 14 30 - 38 3 56 81 - 6 38 - 4 44 67 1 8 - 3 11 19 - 4 26 - 3 30 62 made from the leaves and, using these, the fungi were measured and micro- photographed. 3. One-spore cultures of the fungi were made on potato dextrose agar (PDA). Petri dishes were kept under laboratory conditions (temp. +ls° +2s° C). 4. Inoculation tests were performed on the different species of cereals (two-rowed barley cv. Ingrid, six-rowed barley cv. Otra, oats cv. Ryhti, Spring wheat cv. Ruso, winter wheat cv. Nisu and winter rye cv. Ensi). The cereals were raised to the 2—3 leaf stage in the plant growth chamber. The plants were inoculated with a suspension of spores or mycelia parepared in 220 221 distilled water. After inoculation the plants were kept at -f-120 +ls° C under illumination by day and at +7° +lo° C and in the dark by night for a period of 21 days. 5. The pycnidia and conidia of Septoria species grown on leaves were studied with a microscope. Climate and Weather The weather in summer in 1971, particularly in southern Finland, was characterised by low precipitation, except for part of August. The weather during the growing seasons of 1972 and 1973 was exception- ally warm. Precipitation conditions varied greatly in different parts of the country. In 1972 there was little rain in May and June, whilst in August there was quite a lot of rain in southern and central Finland. During the entire growing season 1973 the amounts of precipitation were subnormal (Meteorol. Yearb. Finland 1971, 1972, 1973). Results Septoria avenae Septoria avenae Frank, Ber. D. Bot. Ges., 13: 64, 1895, perfect stage; Leptosphaeria avenaria Weber, Phytopath. 12: 454, 1922 a. The species has been divided into two formae speciales: L. avenaria Weber f. sp. avenaria Shaw, imperfect stage: S. avenae Frank f. sp. avenae Shaw, Can. J. Bot. 35: 97, 1957, on oats (Avena saliva L.). L. avenaria Weber f. sp. triticea T. Johnson, imperfect stage: S. avenae Frank f. sp. triticea T. Johnson, Can. J. Res. 25 C; 259, 1947, on wheat (Triticum vulgare L.), barley (Hordeum vulgare L.). The formae speciales differ from each other in host range, symptoms and cultural characteristics (Johnson 1947, Shaw 1957 a, 1957 b). Septoria avenae f. sp. avenae S. avenae f. sp. avenae causes speckled blotch, leaf spot or Septoria disease of oats (Weber 1922 a, Huffman 1955, Noble and Montgomerie 1956, Shaw 1957 a). The fungus can be seed borne (Noble and Montgomerie 1956, Richard- son and Noble 1970). It may persist also in the mycelial form on stubble and microspores constituting the primary inoculum (Huffman 1955) or perfect stage (ascospores) are probably the principal spring inoculum (Shaw 1957 a). The fungus is widespread (Frandsen 1943, Sprague 1950), but its eco- nomic importance varies with area and season (Noble and Montgomerie 1956, Shaw 1957 a). In Europe the fungus is a common seedling and leaf pathogen of oats in Scotland (Noble and Montgomerie 1956, Richardson and Noble 1970). It occurs in Germany, particularly in moist conditions (Muller 1963). In Scandinavia S. avenae on oats has been known in Denmark since 1898 (cf. Frandsen 1943) and in Norway (Jorstad 1930, 1945, 1967). Nevertheless, the fungus is of little economic importance. 222 S. avenue has been found also on various grasses (Sprague 1950) The perfect stage Leptosphaeria avenaria was found on oats (Weber 1922 a, Jorstad 1930, Huffman 1955, Shaw 1957 a). Micropycnidia with micro- spores were also found (Johnson 1952, Huffman 1956, Noble and Montgo- merie 1956, Shaw 1957 a). In this study S. avenue f. sp. avenue occurred rarely on oats in the southern parts of the country (Fig. 1). The fungus was encountered only in 3 % of fields (415 fields) studied (Table 1) in the following localities: V: Karinainen, Koski Tl, Piikkiö; U: Anjala, Espoo, Helsinki, Orimattila; EH; Hauho, Hollola, Hämeenlinna, Janakkala, Kangasala, Lammi, Loppi, Riihimäki, Tam- mela, Vesilahti; EP: Laihia: PS: Haukivuori, Jäppilä, Maaninka, Virtasalmi. Perfecta stage, Leptosphaeria avenaria: U: Helsinki, Viikki 6.6. 1972, Snappertuna 24.5. 1972, Tuusula 20.11. 1972. Fig. 1. The occurrence of Septoria avenae i. sp. avenue and Septoria spp. on oats (A vena saliva) by localities in Finland in 1971-1973. 223 Fig. 2. A: Septoria avenae f. sp. avenae on oats, B— C: Leptosphaeria avenaria on winter rye and D— K: Septoria avenae f. sp. triticea; D, E: on winter wheat, F— H: on spring wheat,!, J: on six-rowed barley, K: on two-rowed barley. A, E, G, 1, J, K: pycnospores, x 1 000, except J: x 500; B: ascoma on the dead straw, x 2, C: ascus and sacospores, x 1 000, D and, H: pycnidia on the leaf of wheat, D x 200, H x 100, F: the lesion with black pycnidia on the leaf of spring wheat, X 2. 224 Pycnidia of the fungus were found on ripening and whithering leaves mostly in addition to Helminthosporium avenue Eidam (Mäkelä 1975). Pycnidia measured (100) 146 (162) fi in diam. Macroconidia were cylindrical, rounded at the ends 22.8 55.5 X 2. 4 5.4, 2 5-septa, mostly 37.1 X 3.4 fi, 3.1- septa (Figs. 2 and 6) (cf. Weber 1922 a, Jorstad 1967). Perfect stage, L. avenaria, was found only a few times on overwintered stubble of oats. Septoria avenue f. sp. triticea S. avenue f. sp. triticea causes a leaf blotch of wheat and, less commonly barley (Sprague 1950, Hosford et al. 1969). The fungus probably persists on stubble (cf. Shaw 1957 b). It has not been found in the seed samples (Kietreiber 1962, Richardson and Noble 1970). The fungus has been found on wheat and, less commonly, on barley in Canada since 1943 (Johnson 1947). Today it is still common in Canada (Shaw 1957 b), as well as in the USA (Sprague 1950, Hosford et al. 1969). In Europe the fungus is found in Austria on wheat but is, however, of lesser significance than S. nodorum (Kietreiber 1962). On the other hand the fungus is found commonly in Scotland on wheat and barley (Richardson and Noble 1970, Richardson 1972). Richardson and Noble (1970) believe that S. avenue f. sp. triticea has long been known in Scotland but that it has been frequently misidentified as S. passerinii Sacc. In Finland S. avenue f. sp. triticea was found in 5 % of the barley fields examined in 1970 and 1971 (Mäkelä 1972 b). The fungus infects, besides wheat and barley, also oats, rye and certain grasses, paricularly the species Agropyron and Elymus (Johnson 1947 Srpague 1950). The perfect stage L. avenaria I. sp. triticea has been found on wheat (Johnson 1947, Shaw 1957 b, Hosford et al. 1969). Wheat Septoria avenue f. sp. triticea occurred on wheat in the southern parts of Finland, which are the country’s main wheat-cultivating areas (Figs. 3 and 4, Table 2). The fungus was encountered in 23 % of the fields of spring wheat (222 fields) and in 14 % of the fields of winter wheat (259 fields) examined (Table 1). The fungus was found in the following localieties; Spring wheat V: Karinainen, Kuusjoki, Lemu, Pusula, Pöytyä, Suomusjärvi, Tarvasjoki, Tenhola; U: Inkoo, Pornainen mlk., Porvoo, Tammisaari, Tammisaari mlk., Tuusula; EK: Sippola; St; Kiikka, Mellilä, Punkalaidun; EH: Aitoo, Hattula, Hauho, Janakkala, Kärkölä, Lammi, Pälkäne, Sahalahti, Tuulos, Urjala; ES: Juva, Mäntyharju, Puumala; EP: Jalasjärvi, Laihia, Maksamaa; 225 Table 2. Freguency of Septoria species on spring wheat, winter wheat (Triticum aestivum) and winter rye (Secale oereale) in the fields researched in 1972 and 1973. The samples researched Septoria species. % in the samples researched in the fields Spring wheat Winter wheat Winter rye Spring wheat Winter wheat Winter rye Biological ® « jq 2 d 2 d d 2 IS IS S CV fV 2 S provinces % « ? .-g | w m | « of r inland ° s ■** o ,2 s 0 os = o Sft 1 I I d t 3 I ■Sal do ddodd S 6 3 “~°® ~ - 10 IO « « 1/3 provinces 13 u u ots u-d cr. w IS tfi > o > o of Finland ® _.U_.2—o £ o $ oS o.tioo— oo— o V o V o 7 o -d di oV rt oV rt o’7 rf doddoddod Is x o £ x “g £ x o H w H _H m H H m H A -- 1 1 1 1-(0) (0)- (0) (0) - (0) (0) V 20 31 23 27 28 58 32 19 26 19 5 10 10 4 7 U 18 32 17 37 21 69 22 8 15 22 0 13 9 0 4 EK 1 1 7 11 7 12 (0) 18 17 (0) 1 0 (100) 0 8 St 13 24 26 72 27 96 33 31 31 38 5 10 13 1 4 EH 20 45 39 132 41 177 31 8 14 36 2 13 2 1 1 ES 3 4 14 48 15 52 (50) 13 15 (0) 0 2 (0) 0 0 EP 4 4 12 42 14 46 (0) 19 17 (25) 0 2 (0) 10 9 PH 1 2 19 77 19 79 (50) 1 3 (0) 11 0 (0) 4 4 PS -- 13 28 13 28-14 14- 0 11 - 7 7 PK -- 13 49 13 49-10 10- 0 0 - 8 8 KP 2 4 25 53 26 57 (25) 8 8 0 0 0 (25) 2 4 Kn --6 15 6 15-00- 00 - 77 PP 1 3 14 40 15 43 (0) 13 12 (0) 0 0 (0) 3 2 Ks -- 3 10 3 10-00- 00 - 10 10 KemL -- 2 11 2 11-00- 00 - 00 InL (1) (7) (1) (8) (1) (15) (0) (0) (0) (14) (0) (7) (0) (0) (0) Total 83 150 234 653 251 803 229 V: Aura, Halikko, Karkkila, Kiikala, Laitila, Lemu, Masku, Nauvo, Nummi, Pöytyä, Suomusjärvi. Tenhola, Vihti 1': Anjala, Helsinki, Inkoo, Liljendal, Porvoo mlk., Snappertuna, Tuusula, Vantaa; EK: Vehkalahti, Virolahti; St: Alastaro, Huittinen, Hämeenkyrö, Ikaalinen, Keikyä, Kokemäki, Loimaa, Loimaa mlk., Mellilä, Oripää, Punkalaidun, Vampula; EH: Forssa, Hartola, Hattula, Hauho, Humppila, Hämeenlinna, Koski Hl, Kuhmalahti, Kärkölä, Lammi, Luopioinen, Pälkäne, Renko, Riihimäki, Sahalahti, Somero, Tammela, Toijala, Vesilahti; ES: Juva, Hirvensalmi, Luumäki, Mikkeli mlk.. Mäntyharju, Puumala, Säärainki; EP: Alavus, Jalasjärvi, Kurikka; PH: Sumiainen; PS: Joroinen, Maaninka, Riistavesi; PK: Ilomantsi, Liperi, Tohmajärvi, Valtimo; KP: Kalajoki, Kauhava, Pyhäjoki, Raahe, Sievi; PP: Kemijärvi, Kempele, Liminka, Tyrnävä; InL: Inari. Perfect stage, Leptosphaeria avenaria: U: Helsinki, Viikki 6.6. 1972, PS: Jäppilä 25, 7.1972. Fig. 5. The occurrence of Septoria avenae f. sp. triticea and S. nodorum on spring barley (Hordeum vulgare) by localities in Finland in 1971 1973. 230 Fig. 6. Pycnidia and pycnospores of Septoria species on cereals. A: Septoria avenue f sp. avenae on oats; B— F: S. avenue f. sp. triticea, B, C; on spring wheat, D: on winter wheat, E: on two-rowed barley, F: on six-rowed barley; G —K: S. nodorum, G — I: on spring wheat, J; on winter wheat, K: on spring barley; L, M: S. secalis on vinter rye and N — P: S. Irilici on winter wheat. 231 S. avenue f. sp. Irilicea was found in different years in an average 15 % (range 13—16%) of the fields (803 fields) examined (Table 1). The fungus was rather commoner in two-rowed varieties (21 —34%) than in six-rowed varieties (10—13%). Pycnidia of the fungus were found in greatest abundance on maturing and whithering leaves, i.e. on brown necrotic lesions. Pycnidia were yellowish brown measuring 70 —270 «, averaging 148 fi in diam. Macroconidia were cylindrical 15 46.5 X 26 //, I—s-septa, mostly 31.4 x 3.2 fi, 3.0-septa (Figs. 2 and 6). The perfect stage, L. avenaria, was found only twice on barley. Seploria nodorum Seploria nodorum (Berk.) Berk. & Br. Ann. Mag. Nat. Hist., Ser. 2,5: 379, 1850, perfect stage: Leptosphaeria nodorum Muller, Phytopath. Z. 19: 409, 1952. Syn. cf. Muller 1952: 409. The species has been divided into two formae speciales (Smedegärd Petersen 1974). The fungus causes glume blotch on wheat, attacks all parts of the plant except the roots in all stages of its growth. Leaf lesions often coalescing to form a general leaf necrosis. The fungus is, however, primarily an ear pathogen (Weber 1922 b, Frandsen 1934, Hopp 1957, Jorstad 1967, Brönnimann 1968). On barley the symptoms of the disease are redbrown spots which often continue in the form of chlorotic tissue along the leaf-ribs (Hansen and Magnus 1969, Smedegärd Petersen 1974). The fungus is seed-borne (Machacek 1945, Kietreiber 1961, Hewett 1965, Baker 1971), but can also be found on stubble (Weber 1922 b, Hopp 1957, Scharen 1964, Jones and Odebunmi 1971). It is possible that S. nodo- rum may overwinter also on grasses (Williams and Jones 1973). Epiphytotics have often occurred particularly under moist and rainy climatical conditions (Hopp 1957, Block 1959, Scharen 1964, Jorstad 1967, Brönnimann 1968). S. nodorum occurs widespread in most of the world’s wheat-growing areas (Sprague 1950, C.M.I. map no. 283). In Europe, the fungus was first observed by Berkeley in 1845 in the British Isles (Grove 1935). Today the fungus is very common on wheat (Hewett 1965, Richardson and Noble 1970) and occurs also on barley (Holmes and Colhoun 1970, Richardson 1972). S. nodorum has been known to be common and destructive on wheat also in Germany (Hopp 1957, Block 1959, Bockmann 1963), Switzerland (Muller 1952, Brönnimann 1968), Austria (Kietreiber 1961, 1962) and in the Netherlands (Becker 1955). In Scandinavia S. nodorum has been known to blight wheat in Denmark (Frandsen 1943) and in recent years it has been widespread also on barley (Smedegärd — Petersen 1974). In Norway the fungus is found on wheat and berley. Only on wheat does it appear to be a parasite of economic impor- tance (Jorstad 1930, 1945, 1967, Hansen and Magnus 1969). In Sweden 232 S. nodorum is today quite Common on wheat (Leijerstam 1972) and also on rye (Kolk 1966). In Finland S. nodorum is apparently considered to be of negligible significance because up to now it has not attracted attention. In recent years, however, the fungus was found on barley (Mäkelä 1972 b), and on different grasses (Mäkelä 1972 a). The perfect stage, Leptosphaeria nodorum has been found on wheat in Switzerland (Muller 1952) and in Britain (Lucas and Webster 1967) and on barley in Denmark (Smedegärd — Petersen 1974). S. nodorum infects, besides wheat, barley and rye as well as other species of graminae (Weber 1922 b, Sprague 1950,Hopp 1957, Jorstad 1967, Williams and Jones 1973). Wheat In this study Septoria nodorum occurred on wheat in the southern parts of Finland, where most of the country’s wheat is cultivated, occasionally turning up as far north as Inari, Lapland (Figs. 3 and 4). S. nodorum was more common than S. avenue f. sp. triticea both on spring wheat and winter wheat (Tables 1 and 2). S. nodorum was found in about 1/3 of the wheat fields studied as follows: Spring wheat V: Halikko, Kiikala, Marttila, Muurla, Perniö, Pusula, Pöytyä, Salo, Suomusjärvi, Ten- hola, Vihti; U: Elimäki, Helsinki, Hyvinkää, Kirkkonummi, Lapinjärvi, Nurmijärvi, Snappertuna, Vantaa; St: Hämeenkyrö, Keikyä, Kiikka, Kiukainen, Kokemäki, Lauttakylä, Loimaa mlk., Luvia, Mellilä, Metsämaa, Oripää, Pori, Punkalaidun, Säkylä, Vammala; EH: Asikkala, Forssa, Hattula, Heinola mlk., Humppila, Hämeenlinna, Lammi, Loppi, Pälkäne, Sysmä, Tammela; ES: Juva, Mäntyharju, Puumala, Sulkava, Sääminki; EP: Kurikka, Laihia; PH: Laukaa; PS: Haukivuori, Joroinen, Jäppilä, Kangaslampi, Pieksämäki mlk.; PK: Ilomantsi, Tohmajärvi; Kn: Paltamo; InL: Inari. Perfect stage, Leptosphaeria nodorum V: Tenhola 18.7. 1972, U: Helsinki, Viikki 6.6. 1972, Pornainen 25.5. 1972. Winter wheat V: Halikko, Kaarina, Karjaa, Karjala, Koski Tl, Kuusjoki, Laitila, Lohja mlk . Masku. Muurla, Perniö, Piikkiö, Pohja, Salo, Suomusjärvi, Tenhola, Vehmaa, Vihti; U: Elimäki, Kirkkonummi, Lapinjärvi, Mäntsälä, Nurmijärvi, Sipoo, Siuntio, Tuusula; St: Alastaro, Loimaa mlk., Mcllilä, Oripää, Punkalaidun, Säkylä, Yläne; EH: Hauho, Hattula, Hämeenlinna, litti, Jokioinen, Kangasala, Lempäälä, Loppi, Pälkäne, Riihimäki, Somero, Urjala, Vesilahti, Ypäjä; PH: Laukaa; KP: Paavola. 233 Pycnidia of S. nodorum were found in greatest abundance on ripening and withering leaves, on brownish leafspot as well as on ears (Fig. 7). Pycnidia were yellow brown, measuring 90 300 //, mostly 157 pt in diam. Conidia were short, cylindrical, stright or bent, 10—29 X 1.5—4.5 pi, I—3-septa, mostly 19.7 X 3.0 pi, 1.8-septa (Figs. 6 and 7) (cf. Jorstad 1967). In the inoculation tests (Table 4) it was found that the eleven isolates of S. nodorum which originated from spring and winter wheat and came from different localities, infected barley, wheat and rye, but did not infect oats. The perfect stage, L. nodorum, was found only a few times on spring wheat (Fig. 7). Table 4. Results of the inoculation tests in the laboratory with Septoria species in 1973. The origin of isolates Spring barley !/1o cd cd1d -3 0) o o) Septoria oo - ’S Cereals Localities >. species -g >5 JsgOcK £ Z | W S K 3 8 S>.S> a Au HoC/)oc/)o^o^oOa) S. nodorum Spring barley 3 Two-rowed St: Loimaa, Mellila, PS: Kuopio *** ** *** ** * 0 1 Six-rowed St: Loimaa *** ** ** * 0 5 Spring weat V: Karinainen, Suomus- järvi St: Vampula *** * *** *** ** 0 6 Winter wheat V: Halikko, Karinainen, Piikkiö St: Loimaa, EH; Hattula *•* * *• **• ** 0 1 Winter rye PH: Sumiainen * * *** *** * 0 S. tritici 1 Winter wheat U: Lohja 0 0 * ** * 0 Barley Septoria nodorum occurred on barley in the southern parts of the country, occasionally also as far north as Inari, Lapland (Fig. 5). S. nodorum was found to be moderately common on two-rowed barley in 1/3 of the fields studied, whilst on six-rowed barley it occurred only occasionally. The fungus was found in the following localities: V: Kalanti, Laitila, Masku, Muurla, Pöytyä; U: Anjala, Artjärvi, Hyvinkää, Kirkkonummi, Nurmijärvi, Porvoo mlk., Snappertuna; St: Kiikka, Loimaa mlk., Luvia, Mellilä; EH: Forssa, Hartola, Hauho, Hausjärvi, Heinola mlk., Humppila, Hämeenlinna, Koski HI, Kylmäkoski, Lammi, Loppi, Luopioinen, Orivesi, Renko, Ruovesi, Sahalahti, Somero, Sysmä, Tammela, Tuulos, Vesilahti; ES: Juva; EP: Jalasjärvi; PS: Jäppilä, Kangaslampi, Kuopio; InL: Inari. Perfect stage, Leptosphaeria nodorum: U: Helsinki. Viikki 6.6. 1972; EK: Sippola 1.8. 1972. 234 Fig. 7. Septoria nodorum, A —0: on winter wheat, D: on spring wheat, G: on six-rowed barley, E — H: on two-rowed barley. A: lesions with black pycnidia on glume of ear X5, B: the brown lesion with black pycnidia on tire leaf X 2, C, D, G, H: pycnospores; C, D X 500; G, H X 1 000, E: pycnidia on the leaf, X 200, F: the pycnidium with mass of pycnospores on the leaf X 400, SEM, Viikki. I; Leptosphaeria nodorum, ascospores from spring wheat X 1 000. Pycnidia of S. nodorum were found in withering leaves on necrotic tissues. Pycnidia were light brown, measuring 70 234 p, mostly 138p in diam. Conidia were 12—27 X 2 4.5 p, 0 3-septa, mostly 19.4 X 2.7 p, 1.6-septa (Figs. 6 and 7) (cf. Jorstad 1967). In the inoculation tests (Table 4) it was found that the four isolates of S. nodorum, which originated from two-rowed and six-rowed barley and came from different localities, infected barley, wheat and rye, but did not infect oats. The perfect stage, L. nodorum, was found only twice on barley. Rye Septoria nodorum was found to be very rare on winter rye, occurring in only 4 % of the fields (341 fields) studied (Tables 1 and 2). The fungus was found sporadically throughout the country as far north as Raahe (Fig. 8) as follows: U: Tuusula; St: Loimaa mlk.; EH; Renko, Sahalahti; EP: Jalasjärvi. Koivulahti. Laihia; PH: Konginkangas, Sumiainen; KP; Raahe, Sievi. Perfect stage, Leptosphaeria nodorum: U: Orimattila 25. 5. 1972; EP; Alavus 3. 8. 1973. Pycnidia of S. nodorum were found on ripening leaves (Fig. 9.) Conidia were 12—24 X 2 4.5 p, I—3-septa, mostly 19.9 x 3.3 p, 1.9-septa (Figs. 6 and 9). In the inoculation tests (Table 4) it was found that the isolates of 5. nodorum which originated from winter rye, infected barley, wheat and rye, but did not infect oats. The perfect stage, L. nodorum, was found only twice on rye. Septoria secalies Septoria secalis Prill. & Delacr., Bull. Soc. Myc. Fr., 5: 125, 1889; microform see Sprague 1950: 253, Jorstad 1967: 48. The fungus causes leaf blotch on rye (Weber 1923, Frandsen 1943). The fungus is rarely encountered in the USA (Weber 1923, Sprague 1950) and Europe (cf. Frandsen 1943: 40); lately it has only been reported in Scotland (Richardson and Noble 1970). In Scandinavia S. secalis has been known in Denmark (Frandsen 1943) and Norway (Jorstad 1930, 1945, 1967). The fungus has been reported only on rye and is considered to be econim- ically unimportant (Weber 1923, Jorstad 1930, Frandsen 1943). In this study S. secalis occurred only on winter rye throughout the country as far north as Muhos and Hyrynsalmi (Fig. 8). The disease was observed to occur most commonly in the southwestern and southern parts of Finland, which are the country’s main rye- cultivating areas (Table 2). 7 235 236 S. secalias was found in an average 26 % of the fields (341 fields) examined. In 1973 the fungus was found to be comparatively rarer than in 1972,appar- ently owing to weather conditions (Table 1). The fungus was found in the following localities: V: Kiikala, Korppoo, Koski Tl, Lokalahti, Masku, Mietoinen, Nauvo, Nummi, Raisio, Vehmaa, Vihti; U: Helsinki. Hyvinkää, Inkoo, Lapinjärvi, Tuusula, Vantaa: EK: Sippola; St: Ikaalinen, Huittinen, Kokemäki, Kullaa, Köyliö, Loimaa mlk., Luvia, Mellilä, Oripää, Pori, Punkalaidun; EH; Asikkala, Hattula, Heinola mlk., Humppila, Janakkala, Jokioinen, Kuhmalahti, Kylmä- koski, Kärkölä, Lempäälä, Luopioinen, Pälkäne, Sahalahti, Sysmä, Toijala, Urjala, Vesilahti, Viiala; ES: Juva, Puumala, Sulkava, Sääminki; EP; Jalasjärvi, Laihia; PH: Hankasalmi, Pihtipudas, Sumiainen; PS: Virtasalmi; PK: Ilomantsi, Nurmes; KP: Kannus; Kn: Hyrynsalmi; PP: Muhos. Pycnidia of S. secalis were found in greatest abundance on ripening and withering leaves, on brown necrotic spot. Pycnidia were brown, measuring 72—279 /x, mostly 155 fx in diam. Macro- conidia were cylindrical, rounded at the ends 16.5—54 x 2.5 —5.0 fx, 25- septa, mostly 34.4 x 3.2 /x, 3.0-septa (Figs. 6 and 9) (cf. Sprague 1950, Jorstad 1967). Septoria tritici Septoria tritici Rob. ex Desm., Ann. Sci. Nat., Ser. 2, 17: 107, 1842; syn cf. Frandsen 1943: 14. The fungus causes speckled leaf-blotch mainly on winter wheat ( Sprague 1950, Sanderson 1964). Weakened plants may even die (Frandsen 1943). The fungus has been mainly considered to be a foliar parasite. There have been no confirmed reports of the disease being seed borne (Jones and Cooke 1971, Williams and Jones 1972). It may overwinter on weed species and stubble (Jones and Odebunmi 1971) as well as on grasses (Williams and Jones 1973). S. tritici is widespread and important, particularly in moist conditions (Frandsen 1943, Sprague 1950). In Europe the fungus is found in Britain (Grove 1935), also on spring wheat (Williams and Jones 1973) and in Scotland only rarely on winter wheat (Richardson and Noble 1970). In Scandinavia 5. tritici has been known in Denmark and Sweden since the last century (cf. Frandsen 1943) and in Norway since 1931 (Jorstad 1945, 1967). Today the fungus is little known. 5. tritici mostly infected winter wheat in the spring (Sprague 1950, Jorstad 1945, 1967, Sanderson 1964, Richardsen and Noble 1970) but it also 237 attacked other Trilicum species, rye (Secale cereale L.) (Weber 1922 b, Sprague 1950) and various species of graminae (Grove 1935, Williams and Jones 1973). In this study S. tritici occurred only on winter wheat, being common, partic- ularly in 1973 (Table 1), in the south-western parts of Finland, where most of the winter wheat is grown (Table 2, Fig. 10). The fungus was encountered in 38 % of the fields (259 fields) studied. The localities are as follows: V; Halikko, Kaarina, Karinainen, Karjala, Kiikala, Koski Tl, Laitila, Lohja mlk., Masku, Muurla, Mynämäki, Nummi, Paimio, Perniö. Piikkiö, Pohja, Suomusjärvi, Tenhola; U: Inkoo, Kirrkonummi, Snappertuna, Tuusula; St: Loimaa mlk., Mellilä, Oripää, Yläne; EH: Hattula, Humppila, litti, Jokioinen, Pälkäne, Somero, Ypäjä; KP: Paavola. Pycnidia of S. Irilici were found abundantly only in the spring (May-early August), on brown greyish brown yellowish brown leaf spots (Fig. 9). Fig. 8. The occurrence of Septoria secalis and S. nodorum on winter rye (Secale cereale) by localities in Finland in 1972 and 1973. 238 Fig. 9. A —C: Septoria secalis on winter rye, D — H: S. tritici on winter wheat. A. D: the brown lesions with black pycnidia in the leaves, X 2; B, G, H: pycnidia in the leaves. B, G X 200, H x 400; C, E, F: pycnospores, C, F x 750, E x 1 000. 239 Pycnidia were blackish brown flattened, measuring (62) 117 x 129 (204) [i in diam. (Figs. 6 and 9). Macroconidia were obclavate filiform, slightly curved, 24 —BO X I—3 [x , I—6-septa, mostly 55.5 x 2.0 fi 3.2 —septa (Figs. 6 and 9) (cf. Jorstad 1967). Discussion This study is based on samples of cereals gathered during three growing seasons (1971 1973), except for wheat and rye samples, which were only gathered during two growing seasons (1972—1973). The weather during the growing seasons of 1972 and 1973 was exceptionally warm and there was less precipitation than normal although rainfall varied greatly in different parts of the country (cf. p. 221). On the other hand it is known that epiphytotics of Septoria species have often occurred, particularly under moist and rainy conditions (Hopp 1957, Block 1959, Muller 1963, Scharen 1964, Jorstad 1967, Brönniman 1968). Fig. 10. The occurrence of Septoria tritici on winter wheat (Triticum aestivum) by lecalities in Finland in 1972 and 1973. 240 In any event this study has clarified the interrelationships of Septoria species on different cereals as well as their relation to other pathogens causing leaf-spot diseases, such as Helminthosporium species and Rhynchosporium secalis (Oud.) J. J. Davis (cf. Mäkelä 1974, 1975). Septoria species occurred most commonly on wheat and two-rowed barley, which are primarily cultivated in southern and southwestern Finland. It was in this area that the fungi were observed to thrive. On the other hand, on six-rowed barley, too, Septoria species were more common in southwestern Finland than in Ostrobothnia. The reverse held for the Helminthosporium species, which in the same samples of cereals were observed to be most abundant in Ostrobothnia (cf. Mäkelä 1975). Septoria nodorum occurred on wheat, particularly as a foliar parasite. In some cases it was observed to affect the ears of spring wheat so severely that the field turned a dark grey colour (St: Vampula, Aug., 1973). Likewise S. nodorum was found to occur according to the author very common and abun- dantly on ears of winter and spring wheat in many fields located in southwestern Finland in the exceptional rainy growing season 1974. The significance of the fungus in causing glume blotch of wheat can hardly be as large in Finland as it is in other countries (cf. Hopp 1957, Hewett 1965, Jorstad 1967, Brönni- mann 1968, Richardson and Noble 1970). This is simply due to the small area in which wheat is cultivated. Of Finland’s total field area (2 665 000 hectars), spring wheat occupies less than five per cent and winter wheat less than two per cent. The fungus also occurred on barley, particularly on two- rowed varieties (cf. Jorstad 1967) but is apparently of little significance, as has been observed in other countries (Hansen and Magnus 1969, Richardson 1972). According to Smedegäd Petersen (1974), the fungus is an important pathogen on barley in Denmark. The present study showed that S. nodorum occurred rather commonly not only on cereals but also on numerous cultivated and wild grasses (cf. Mäkelä 1972 a). This confirmes that S. nodorum occurs commonly in Finland. In other countries has also been known the occurrence of the species on grasses (Sprague 1950, Hopp 1957, Jorstad 1967, Teterevnikova Babayan and Bokhyan 1970, Williams and Jones 1973). The fungus is regarded as being a very weakly specialised species (Weber 1922 b, Hopp 1957, Brönni- mann 1968). This opinion is supported by the laboratory inoculation tests performed in this study, in which isolates of S. nodorum originating from different cereals infected not only their own host but also all other cereals except oats (cf. Holmes and Colhoun 1970). This conclusion runs counter to the results obtained by Smedegärd Petersen (1974). Septoria tritici occurred exclusively on winter wheat, especially in the spring of 1973, and caused severe seedling-leaf mortality. Similar observations have been made elsewhere (Sanderson 1964, Jorstad 1967, Richardson and Noble 1970). The fungus is held to be strictly a foliar parasite, though it is capable of infecting all parts of the plant (Jones and Cooke 1971). In the field, however, the fungus was not observed on spring wheat, on which it is known to occur in, for example, Britain (Jones and Odebunmi 1971, Williams and Jones 1972, 1973), nor was it observed on rye (cf. Weber 1922 b. 241 Sprague 1950). In the laboratory inoculation tests, however, isolates of 5. tritici originating from winter wheat infected not only their own host but also spring wheat and rye. Septoria avenae f. sp. triticea occurred rather commonly on wheat and barley. The fungus is apparently a pathogen of minor importance in Finland for it is considered to be a weak parasite (Johnson 1947, Shaw 1957 b). Simi- larly, on wheat it is considered to be of far less significance than S. nodorum (Kietreiber 1962). This study has shown that besides occurring on cereals, S. avenae f. sp. triticea is also found on numerous grass species, apparently as a saprophyte (cf. Johnson 1947, Sprague 1950). Septoria avenae f. sp. avenae is of quite negligible importance on oats owing to its sporadic occurrence. Similarly, S. secalis, which occurs to some extent on rye, is generally considered to be economically insignificant (Weber 1923, Jorstad 1930, Frandsen 1943). The perfect stage (Leptosphaeria avenaris and L. nodorum) were found on all cereals and on numerous grasses, as were the corresponding Septoria species. The present study did not clarify the role these play in the surviving and transmission of fungi. In other countries there is also knowledge about the occurrence of the same Septoria species on cereals and grasses (Weber 1922 b, Sprague 1950, Jorstad 1967, Teterevnikova—Babayn and Bokhyan 1970, Williams and Jones 1973). Acknowledgements. I wish to express my thanks to Mr. Jorma Kurtto, M.Sc., Mr. Aarne Kurppa, M.Sc., and Mr. Leo Mustonen, M.Sc. who assisted me in the collection of samples of cereals. I have obtained much valuable information about Septoria species from Mr. Leo Mus- tonen, who has carried out the inoculation tests. I am grateful to Mrs. Hilkka Koponen, M.Sc., for valuable information about Leptosphaeria species, on which she is presently doing research. I whish to thank the University of Helsinki and the National Research Counsil for Agriculture and Forestry for their financial assistance. REFERENCES Baker, C. J. 1971. Morphology of seedling infection by Leptosphaeria nodorum. Trans. Brit. Mycol. Soc. 56:306-309. Becker, G. J. F. 1955. Onderzoek naar de afrigpingsziekten van tarwe. Tienjaren pian voor graanonderzoek. Verslag over het tweede jaar 2:87 95. Wageningen. Block, G. 1959. Untersuchungen fiber die Braunfleckigkeit (Spelzenbräune) des Weizens (Septoria nodorum Berk.) insbesondere in Bezug auf Infectionsbedingungen. Sor- tenanfälligkeit und wirtschaftliche Bedeutung des Pilzes. Z. Acker-Pflßau 107; 435 458. Bockmann, H. 1963. Kunstliche Freilandsinfektionen mit den Erregern der Fuss- und Ähronkrankheiten des Weizens. Nachrichtenbl. Deutsch. Pfl. schutzd. (Braunschweig) 15: 33-37. Brönnimann, A. 1968. Zur Kenntnis von Septoria nodorum Berk., dem Erreger der Spelzen- bräune und einer Blattdiirr des Weizens. Phytopath. Z. 61: 101 146. 242 Cooke, B. M. & Jones, D. G. 1971. The epidemiology of Septoria tritici and S. nodorum 111. The reaction of spring and winter wheat to infection by Septoria tritici and S. nodorum. Trans. Brit. Mycol. Soc. 56; 121 135. Frandsen, N. O. 1943. Septoria-Arten des Getreides und anderer Gräser in Dänemark. Medd. PL pathol. Afd., No 26, K. Vet. Landbohojsk. 92 p. Kobcnhavn. Grove, W. B. 1935, British stem- and leaf-fungi (Coelomycetes). I. 488 p. Cambridge. Hansen, L. R. & Magnus, H. A. 1969. Leaf spot fungi on barley in Norway. Norwegian PI. Prot. Inst. Div. PI. Path,, Vollebekk. Rep. No. 42. Heikinheimo, O. & Raatikainen, M. 1971. The recording of localities of biological finds in Finland. Ann. Ent. Fenn. 37, la: 1 27. Hewett, P. D. 1965. A survey of seed-borne fungi of wheat. I The incidence of Leptosphaeria nodorum and Griphosphaeria nivalis. Trans. Brit. Mycol. Soc. 48: 59 72. Holmes, S. J. I. & Colhoun, J. 1970. Septoria nodorum as a pathogen of barley. Trans. Brit. Mycol. Soc. 55: 321 325. Hopp, H. 1957. Untersuchungen iiber die Braunfleckigkeit des Weizens und ihren Erreger Septoria nodorum Berk. Phytopath. Z. 29: 395—412. Hosford, R. M., Jr., Hogenson, R. 0., Huguelet, J. E. & Kiesling, R. L. 1969. Studies of Leptosphaeria avenaria i. sp. triticea on wheat in North Dakota. PI. Dis. Rep. 53: 378 -381. Huffman, M. D. 1955. Disease cycle of Septoria disease of oats. Phytopath. 45: 278 280. Johnson, T. 1947. A form of Leptosphaeria avenaria on wheat in Canada. Can. J. Res. 25, C: 259-270. Jones, D. G. & Cooke, B. M. 1969. The epidemiology of Septoria tritici and S. nodorum. Trans. Brit. Mycol. Soc. 53: 39 46. » & Odebunmi, K. 1971. The epidemiology of Septoria tritici and S. nodorum. IV. The effect of inoculation at different growth stages and on different plant parts. Trans. Brit. Mycol, Soc. 56, 2:281 288. Jorstad, I. 1967. Septoria and Septorioid fungi on Graminea in Norway. Skr. norske Vidensk. Akad. I. Mat. Naturv. KL N. S. No. 24. Kietreiber, M. 1961. Die Erkennung des Septoria-~Beia\\es von Weizenkorncrn bei der Saatgutpriifung. Pfl. schutzber. 26: 129 157. » 1962. Die Krankheitsbefall der Saatgutprobenim Jahre 1961. Z. Bodenkultur 13: 21 27. Kolk, H. 1966. Utsädesburna svampsjukdomar pä. sträsäd. Kgl. Lantbr. Akad, Tidskr. 105: 353-375. Leijerstam, B. 1972. Graderingar av angrepp av Septoria nodorum i vete 1963 1968. Medd. Stat. Växtskyddsanst. 15: 289—305. Lucas, M. T & Webster, J. 1967. Conidial states of British species of Leptosphaeria. Trans. Brit. Mycol. Soc. 50: 85 121. Machacek, J. E. 1945. The prevalence of Septoria on cereal seed in Canada. Phytopath. 35: 51-53. Muller, E. 1952. Pilzliche Erreger der Getreideblattdiirre. Phytopath. Z. 19: 403—416. Möller, H. J. 1963. Untersuchungen iiber Blattfleckenkrankheiten des Hafers. Phytopath. Z. 49: 266-290. Mäkelä, K, 1972 a. Disease damage to the foliage of cultivated grasses in Finland. Acta Agr. Fenn. 124, 1: 1—56. * 1972 b. Leaf spot fungi on barley in Finland. Acta Agr. Fenn. 124, 3: 1 23. » 1974. Occurrence of Rhynchosporium secalis (Oud.) J. J. Davis on spring barley and winter rye in Finland. J. Scient. Agric. Soc. Finl. 46: 103 117. » 1975. Occurrence of Helminthosporium species on cereals in Finland in 1971 —1973. J. Scient. Agric. Soc. Finl. 47: 181 217. Noble, M. & Montgomerie, I. G. 1956. Griphosphaeria nivalis (Schaffnit) Milli. & Arx and Leptosphaeria avenaria Weber on oats. Trans. Brit. Mycol. Soc. 39: 449 459. Richardson, M. J. 1972. Septoria on barley in Scotland 1970 1971. Trans. Brit. Mycol, Soc. 58:507-510. » & Noble, M. 1970. Septoria species on cereals a note to aid their identification. PL Path. 19:159-163. 243 Sanderson, F. R. 1964. Effects of leaf spot (Septoria tritici) in autumnsown wheat crops. N. Zeal, wheat Rev. 9: 56 59. Scharen, A. L. 1964. Environmental influences on development of glume-blotch in wheat. Phytopath. 54: 300 303. Shaw, D. 1957 a. Studies on Leptosphaeria avenaria f. sp. avenaria. Can J. Bot. 35: 97 112. » 1957 b. Studies on Leptosphaeria avenaria f. sp. trilicea on cereals and grases. Can. J. Bot. 35: 113-118. SmedegArd Petersen, V. 1974. Leptosphaeria nodorum (Septoria nodorum). A new pathogen on barley in Denmark and its physiologic specialization on barley and wheat. Friesia 10: 251-264. Sprague, R. 1950. Diseases of cereals and grasses in North America. 538 p. New York. Teterevnikova babayan, D, N. & Bokhyan, M. V. 1970. Obzor vozbuditelei septoriozov Pyreya v Sovetskom Soyuze. (Survey of the causal agents of septoriosis of wheatgrass in the Soviet Union.) Mikol. i Fitopatol. 4,1: 18 —27 (Ref. Rev. PI. Path. 49: 365). Weber, G. F. 1922 a. Septoria diseases of cereals. Phytopath. 12:449—470. » — 1922 b. Septoria diseases of wheat. Phytopath. 12:537 585. » 1923. 111. Septoria disease of rye, barley and certain grasses. Septoria leaf blotch of rye. Phytopath. 13:1 23. Wenham, H. T. 1959. Studies on Septoria leaf blotch disease of wheat (Triticum aestivum L.) caused by Septoria tritici Desm. N. Zeal. J. Agric. Res. 2: 208 213. Williams, J. K, & Jones, D. G. 1972. Epidemiology of Septoria tritici and S. nodorum. VI. Effect of time of initial infection on disease development and grain yield in spring wheats. Trans. Brit. Mycol. Soc. 59:273 283. —» & Jones, D. G. 1973. Infection of grasses by Septoria nodorum and S. tritici. Trans. Brit. Mycol. Soc. 60 :355 —358. Selostus Septoria-sienien esiintymisestä viljakasvustoissa vuosina 1971—1973. Kaiho Mäkelä Helsingin yliopiston kasvipatologian laitos, Viikki Tutkimuksessa selvitettiin Septoria-lajien levinneisyyttä ja merkitystä viljoilla. Tulokset perustuvat pääosin kasvukausina 1971 1973 kautta maan 315 paikkakunnalta, etupäässä viljelijäin pelloilta kerättyihin 2 040 viljanäyttceseen. Kaikki näytteet tutkittiin silmävaraisesti ja mikroskooppisesti. Sienet mitattiin ja valoku- vattiin, osa niistä viljeltiin keinoalustalla sekä tehtiin saastutuskokeita laboratorio-oloissa. Septoria-lajeja esiintyi kaikilla viljoilla, yleisimpänä vehnällä ja 2-tahoisella ohralla, jossain määrin rukiilla, harvinaisena monitahoisella ohralla ja kauralla. Septoria-lajeja esiintyi runsaimmin maan lounais- ja eteläosissa; Varsinais-Suomessa, Uudella- maalla, Satakunnassa ja Etelä-Hämeessä. Sensijaan niitä oli erittäin vähän Pohjanmaalla ja maan pohjoisosissa tuskin lainkaan. Septoria nodorum (Berk.) Berk. & Br. esiintyi yleisimpänä lajina sekä kevät- että syys- vehnällä ja melko yleisenä 2-tahoisella ohralla. Sientä todettiin n. l/3;ssa tutkituista pelloista ja vehnällä n. 60 —7O °(,:ssa sekä ohralla n. 40 %:ssa paikkakunnista. Sensijaan monitahoisella ohralla ja rukiilla S. nodorumi a esiintyi harvinaisena, 2 4 %:ssa tutkituista pelloista ja n. 6 10 %:ssa paikkakunnista. Kauralla ei sientä varmuudella todettu lainkaan. 244 Myös S. nodorumin eri viljoista eristetyt kannat, joita tutkittiin laboratorio-oloissa, saastut- tivat isäntäkasvinsa lisäksi kaikkia muitakin viljalajeja, kauraa lukuunottamatta. Sienen suvullinen aste, Leptosphaeria nodorum Muller, tavattiin muutaman kerran kevät- vehnällä, ohralla ja rukiilla. Septoria avenae Frank, f. sp. triticea T. Johanson esiintyi yleisimpänä 2-tahoisella ohralla, n. l/3:ssa ja vehnällä vaajaassa l/4:ssa tutkituista pelloista ja kummallakin n. 35 —45 %:ssa paikkakunnista. Rukiilla ja kauralla ei sientä todettu lainkaan. Sienen suvullinen aste, Leptosphaeria avenaria Weber f. sp. triticea T. Johnson tavattiin muutaman kerran kevätvehnällä ja ohralla. Septoria avenae Frank f. sp. avenae Shaw esiintyi vain kauralla harvinaisena, n. 3 %:ssa tutkituista pelloista ja vajaassa 10 %:ssa paikkakunnista. Sienen suvullinen aste, L. avenaria Weber f. sp. avenaria Shaw, löytyi myös kauralta muutaman kerran. Septoria tritici Rob. ex Desm. todettiin vain syysvehnällä n. 40 %:ssa tutkituista pelloista ja n, l/2:ssa paikkakunnista. Sientä esiintyi vain keväällä, joskus hyvinkin runsaana ja leh- distöä tuhoavana. Sieni saastutti laboratorio-oloissa syysvehän lisäksi jonkin verran kevät- vehnää ja ruista. Septoria sesalis Prill. & Delacr. esiintyi vain rukiilla melko yleisenä n. l/4:ssa tutkituista pelloista ja n. l/2:ssa paikkakunnista. Septoria-\a.jien esiintymisessä oli tiettyä yhdenmukaisuutta eri vuosina. Vain syysvehnällä ja rukiilla esiintyi eräitä Septoria-lajeja vähemmän v. 1973 kuin v. 1972. Tähän on ilmeisesti syynä kesän 1973 poikkeuksellisen aikainen ja nopea tuleentuminen kuumuuden ja kuivuuden seurauksena. Septoria-sienten aiheuttamien tautien vaikutus satoon jää selvittämättä tässä tutkimuk- sessa. S. triticitä. lukuunottamatta nämä sienet esiintyivät vasta viljan tuleentumisvaiheessa yhdessä muiden sienten kuten Helminthosporium-, ruoste- ja härmäsienten kanssa. Lisäksi saattoi useita Septoria-\rL]e]2L esiintyä viljassa samanaikaisesti. On ilmeistä, että Septoria- sienten merkitys meillä jää vähäisemmäksi kuin monissa muissa maissa jo yksistään siitä syystä, että niiden tärkeimmän isäntäkasvin vehnän viljelyala on verraten pieni. Monien Septoria- lajien, kuten S. nodorum, S. tritici ja S. avenae f. sp. Iriticeae tiedetään säi- lyvän talven yli viljan sängessä ja kasvijätteissä, ilmeisesti myös heinissä. S. nodorum leviää myös siemenen mukana. Millä tavoin viljojen Septoria-sienet meidän oloissamme säilyvät ja leviävät ja mikä osuus siinä on suvullisella Leptosphaeria-asteella ja heinillä, jää avoimeksi tässä tutkimuksessa.