OVERWINTERING OF GRAMINEAE-PLANTS AND PARASITIC FUNGI. I. SCLEROTINIA BOREALIS Bubäk & Vleugel. E. A. Jamalainen. Agricultural Research Institute, Department of Plant Pathology Received 1. 6. 1949 The main causes of the poor overwintering of cereals and grasses in Finland are the fungi damaging the plants during their overwintering. This study, which is to be published in parts, will give an account of the role these fungi have in the cultivation of winter cereals and grasses in our country. The Sclerotinia borealis Bubåk & Vleugel, which is met in the middle and northern parts of Sweden and Finland, is first taken under study. Introduction. Sclerotinia borealis was noted in Luleå, Sweden, for the first time in Dactylis glomerata by Ulander (17, p. 47) in 1906. Later it has been noted very commonly in the middle and northern parts of Sweden, especially in Norrbotten in winter rye and other Gramineae-plants (Ulander and Ekstrand in many papers, cf. references). In 1917 Vleugel (21, p. 3QB) described the fungus by the name Sclerotinia borealis Bubäk & Vleugel. During an excursion made with Mr. H. Ekstrand, Fil. Lic., to the northern and middle Finland in spring 1946 the author noted that S. borealis was in many dist- ricts quite common in winter rye and timothy (14). In the next three years investi- gations were continued by the Department of Plant Pathology in order to find out the spreading of the fungus and the damages caused by it. In spring 1948 the author had an opportunity of making an excursion with Ekstrand also to the north of Sweden where overwintering of cereals and grasses was examined. In the Soviet Union, too, a fungus similar to S. borealis is met with, Sclerotinia graminearum Elenev, which causes injury to overwintering Gramineae-plants chiefly in north-eastern parts of European Russia. Reports on S. graminearum in https://c-info.fi/en/info/?token=yrVuQjZAWYnl0KQT.dWrNa8ELndphxfuCSRLD8w.rezx082FOFH2EstUh3-K13A8MneehdJbOOPyQZt9WJhyg1sxU865PfDXK0mbG2d-2GqtU4fjuIfOUzNp8ivoA2ec-ebXN-dVUm0ZD7jegzCY9mWXJAJZJAH2PrRwLlir2tAZnRUUyUwv2BEg-3GEgrGX7h5cmzZLRACRMdaS 126 E. A. JAMALAINEN Table i. Measurements oj the size relations of the sclerotia of Sclerotinia bore a I i Taul. 1. Mittauksia Sclerotinia borealisen sklerotioiden suuruussuhteista. io sclerotia measured of each sample; average measures in mm, the variations in brackets. Kustakin näytteestä mitattu 10 sklerotiota; mitat keskimäärin mm:ssä, sulkeissa vaihtelut Length Pituus Breadth ThicknessHost plant and its growing place Isäntäkasvi ja sen kasvupaikka Leveys Paksuus Festuca rubra, Tohmajärvi 3.59 (5.1 —2.8) 2.24(3.0—1.7) ].56(2.0—1.0) Poa serotina, Apukka 2.21 (2.8—1.9) 1.(52 (1.8—1.4) 0.94 (1.3—0.6) P. trivialis, Apukka 2.38 (2.8-—1.9) 1.48 (1.9—1.1) 0.91 (1.2—0.6) Phleum pratense, Rovaniemi 2.92 (4.8-—2.3) 1.91 (2.7—1.4) 1.31 (1.9—0.6) » » Pielisensuu 3.28(4.6—2.0) 1.82 (2.3—1.1) 1.34(1.7—1.0) » » Tärändö, Sweden 3.34 (5.0—1.8) 1.84 (2.7—1.0) 1.29 (1.9—0.9) » » Karunki 3.43 (4.8—2.4) 1.82 (2.3—1.0) 1.19(1.8—0.8) ,> ’ » Kemijärvi 3.60(5.9—2.4) 2.01(2.4—1.3) 1.39(1.9—0.8) » » Ramia 3.39 (4.2—3.0) 2.06 (2.8—1.7) 1.32 (1.8—1,0) Secale cereale, Tohmajärvi 3.44(4.6—2.1) 1.92 (2.3—1.4) 1.31 (2.0—1.0) » » Apukka 4.29(5.9—3.0) 2.30 (3.8—1.4) 1.51(3.0—1.0) » » Apukka 3.93 (6,0—3.1) 2.12(2.7—1.4) 0.90(1.2—0.6) The same as above, sclerotia in water for 2 days Sama kuin edellä, sklerotiot 2 vrk. vedessä . . 4.53((6.3.5)5—3.5) 2.24((2.1.5) 1.20((1.0.9) Triticum sativum, Apukka 3.69 (4.7—2.8) 1.94 (2.4—1.6) 1.30(1.8-—0.9) Dry sclerotia on the average Kuivat sklero- tiot keskimäärin 3.35 (6.0—1.8) 1.93 (3.8—1.0) 1.25 (3.0—0.6) Russia are known since 1901 when it, according to Elenev (cf. Solkina, 16, p. 100) caused damage to winter rye in the governement of Vjatka (present Kirov Region). In 1919 Elenev named the fungus Sclerotin'a graminearum not describ- ing it more exactly. In 1939 Solkina defines more closely S. borealis Elenev with Latin descriptions (16). She arrives at the result that 5. graminearum Elenev described by her resembles most to 5. borealis Bubåk & Vleugel. Sol- kina (16, p. 105) regards, however, 5. graminearum as a separate species, at the same time pointing out that because of insufficient knowledge of the biology of the fungus the question cannot be held as finally settled, and continued in- vestigations may lead to including of S. graminearum among the closely related species. The morphology and biology of the fungus and the influence of growing conditions on its appearance. The sclerotia of the Sclerotinia borealis are, according to Vleugel’s description (21, p. 308), s—B5—8 mm long, 2—4 mm wide, often curved or flat, first dirty- coloured. later black. Out of the sclerotium grow I—31 —3 apothecia which are cup- shaped and lightbrown. The asci are cylinder-shaped, consisting of 8 spores, 190— 210 [x long and 9—13 [x thick. The ascospore are straight, one-celled, elliptic or longish the elliptic ones 19-—2 Bjx long and 7—ll jx wide. The above description by Vleugel on S. borealis corresponds to the idea formed by the author. In the appended table 1 some figures of the size relations of the sclerotia of S. borealis are given. The measurements have been made with dry herbarium material collected by the author. The sclerotia of one sample has, besi- des, been kept in water for two days and measured after that. As the measurements show, the sclerotia had swollen in water. Accordingly, the sclerotia collected in the growing places are larger in size than they are later when dry. The figures given in the table show further that the sclerotia in rye and wheat are somewhat larger than in timothy and Port-species. The size of the sclerotia is thus influenced by the size of the foliage of the host plant and apparently also by the conditions in which the host plants have grown. The width of the cup of the apothecia was in the mea- surements by the author the fol- lowing: young apothecia 0.5— 2.1 mm., older apothecia 2—4 mm; the length of the stalk of the apothecia varied between 3.3—9.6 mm (Fig. 1). The size of the asci was the following: the average length 210 g. (ran- ging from 180 to 250) and thickness 10 [x (8—14). The ascospore, eight in each ascus, were elliptic in shape; their size was 9—22 g, on the average. The best time to discover 5. borealis is spring, directly af- ter the snow has melted. The young crops of winter cereals and other Gramineae-plants ha- ving come forth from under the snow, larger or smaller areas of Fig. 1. Sclerotia of Sclerotinia bo- realis with apothecia. X 3. Photo by H. Roivainen & E. A. Jumalainen. Kuva 1. Sclerotinia borealisen sieni rihma- pahkoja itiöemineen. x 3. Fig. 2. Timothy thinned by Sclerotinia borealis. Photo by E. A. Jamalhinen Kuva 2. Sclerotinia borealisen harventamaa timoteitä. 127OVERWINTERING OF GRAMINEAE-PLANTS AND PARASITIC FUNGI E. A. JAMALAINEN128 vegetation in a field infected by the fun- gus have been destroyed (Fig. 2). Under wet conditions, grey mycelium can then be seen on the surface of the leaves in the infected plants (cf. 17, p. 47). Ac- cording to the writer’s observations, it is typical of the disease that the leaves killed by the fungus are, when dry, more or less thready, grey or greyish-brown in colour (Fig. 3). In this respect, the damages caused by S. borealis and by snow mould due to Fusarium nivale (Fr.) Ces. are easily distinguishable from each other. The leaves of the plants injured by F. nivale are, even when dry, spread out and often a little reddish. In spring, apparently immediately after the snow has melted, S. borealis begins to form sclerotia. The damages caused by S. borealis may increase in the course of spring so that at the time the melting of snow takes place, more plants are alive than later on. The plants damaged by the fungus have no strength to live. This was discovered by Ekstrand (6, p. 47) in Sweden. He mentions that this happens in spring when the temperature is low and there is plenty of moisture. On the other hand, the plants that are weak because of the fungus may become stronger later on, as was discovered in Finland, at the Perä-Pohjola Agricultural Experi- ment Station in 1948 (cf. p. 131). According to the experiments performed by the author, apothecia began to appear in the sclerotia of S. borealis gathered in spring only in autumn when the weather had become colder, in September-October. The sclerotia were kept out- side during the summer. In laboratory conditions, the appearance of apothecia is not normal. Often the stalk only is formed. The apothecia are positively photo- tropic. It is obvious that the sclerotia of S. borealis require a ripening time which is as long as the growing time in sunlight so as to be able to produce normally developed apothecia with ascorpore. Information about the spreading of S. borealis show that it favours northern regions. The climatic conditions prevailing in these regions must have a decisive influence on its occurrence. A long, moist and warm autumn, when the snow falls on frostless ground, is obviously advantageous to the spreading of the fungus. Further, we may conclude that freezing of soil, on the one hand, and the thick- ness of the snow layer, on the other, and its quicker or slower melting affect the damages caused by the fungus in spring. If the freezing of soil is low and the Fig. 3. Sclerotinia borealis in win let rye. x 2. Photo by E. A. Jumalainen. Kuva 3. Sclerotinia borealis syysrukiissa. x2. OVERWINTERING OF GRAMINEAE-PEANTS AND PARASITIC FUNGI 129 snow layer thick, and the snow melts slowly in spring, the fungus has great possibi- lities to cause damage. During the four years information on 5. borealis has been available by the author in Finland, its damages were greatest and the area of its appearance most extensive in 1946, as shown in pp. 131—132. In the following three springs the occurrence of the fungus was considerably slighter. In 1948—49 it caused direct damages only in the vicinity of the Perä-Pohjola Experiment Station near Rovaniemi. What this is due to, is difficult to conclude on the basis of the information on the climatic conditions, snow, and freezing of soil available then. So, e.g., the overwintering period 1947—48 was everywhere in Finland favourable to the damages of snow mould. S. borealis was then, however, not met with to a great extent. The question of the influence of climatic conditions on the greater or lesser appearance of S. borealis requires detailed studies, when, among other things, measurements of temperature and moisture in the areas of the occurrence of the mgus should be made in autumn as well as under the snow in spring. Occurrence of the fungus in different countries. Reports on the occurrence' of Sclerotinia borealis have been received by the ruthor from Sweden and Finland only. They will be elaborated in the following. Sweden. Information of the occurrence of S. borealis in Sweden were based earlier on the studies of Ulander (17, 18, 19) and lately on those of Ekstrand. The latter has annually reported on the significance of the fungus in Sweden in the periodical Växtskyddsnotiser. The area of occurence of the fungus extends in Norrland in Sweden, according to Ekstrand (10, p. 23), up to Dalarna and Gästrikland (in la- titude abt. 61° N). • The damages caused by S. borealis in Sweden have been every year greatest in the country Norrbotten. Most abundant was the occurrence according to Ekstrand in the springs 1942 (4) and 1946 (6). In 1946 the fungus caused injury in the whole Norrland. In many instances timothy had either entirely or for the most part disappeared especially from the first-year fields north of the arctic circle. Ekstrand ascribes this to the fact that the soil had only slightly if at all frozen in the preceding autumn, and in the spring snow stayed long on the ground. In other years, too, except those mentioned, Ekstrand noted occurrence of the disease in Sweden but not in so injurious a degree as in 1942 and 1946; .g., in 1948 the damages were slight (12) Finland. Valle, (20, p. 159—160) discovered at Tammisto (Plant Breeding Station of Hankkija at Malmi near Helsinki) in the spring of 1930 a fungus in timothy which 130 E. A. JAMALAINEN he modified to S. borealis. In the timothy strains that had had the poorest over- wintering, 10 specimens out of 25 had been destroyed. The plants killed by the disease either died entirely or else only a few green leaves appeared on the injured plants. Besides timothy in 1930, damages by the fungus appeared during the overwintering at Tammisto also in cocksfoot in 1927. Reports on 5. borealis in Finland, which have been collected by the author, date from 1946. Material so far accumulated at Agricultural Research Institute, Department of Plant Pathology, on the fungus and its areas of occurrence is given in the following 1 . Agrostis canina L. Ob. Rovaniemi, Apukka, Exp. Sta, 31. ö. 48; E. A J.-; 27.5. 49: E. A. J. A. stolonifera L. Ob. Rovaniemi, Apukka, Exp. Sta, 27.5. 49: E. A. J. Alopecurus pratensis L. Ob. Rovaniemi, Apukka, Exp. Sta., 27.5. 49: E. A. J. Anthoxanthum odoratum L. Ob. Rovaniemi, Apukka, Exp. Sta., 27.5. 49; E. A. J. Bromus inermis Leyss. Ob. Rovaniemi, Apukka, Exp. Sta., 31.5. 48; E. A. J.2 . Dactylis glomerata L. Ob. Rovaniemi, Apukka, Exp. Sta., 31.5. 48: E. A. J.2; 26.5. 49; E. A. J. Festuca pratensis Huds. Ob. Rovaniemi, Apukka, Exp. Sta., 27.5. 49; E. A. J. F. rubra L. Kb. Tohmajärvi, Exp. Sta., 7.6. 46: E. A. J. Ob. Rovaniemi, Apukka, Exp. Sta., 31.5.48; E. A. J . 2 ; 27.5.49: E. A. J. Lolium perenne L. Sb. Maaninka, Exp. Sta., 15.5. 48; E. A. J. Ob. Rovaniemi, Apukka, Exp. Sta., 27.5. 49: E. A. J. Phleum pratense L. Sa. Mikkeli, rural community, 4.5. 48: A. Ylimäki. Sääminki, Nojamaa, 5.5. 48: A. Ylimäki. Sb. lisalmi, 17.8. 46: J. Paltemaa. Maaninka, Exp. Sta., 8.6. 48, from different parts of peat and mineral soil: H. Ekstrand; 4. 7. 47, from peat and mineral soil; E. A. J.; 3. 5. 49, from peat soil; E. A. J. Kb. Kontiolahti, Lehmo 2. 6. 47; E. A. J. Pielisensuu, Mustola, 2. 6. 47: E. A. J. Tohma- järvi, Exp. Sta., 7. 6. 46 and 2—’3. 6. 47, from peat and mineral soil; E. A. J.; 13. 5.48, from mineral soil: E. A. J. Tohmajärvi, church village, 7. 6. 46 and 3. 4. 47, from different parts of timothy fields; E. A. J. Ob. Karunki, Ojanperä, Korpikylä and Palovaara, 27. 4. 48: A. Alakarhu. Kemijärvi, Joutsi- järvi and Puikkala, 1. 6. 48; E. A. J. Ranua, Ylisimo, 10.5.48: A. Witikainen. Rovaniemi, Apukka, Exp. Sta., 2. 6. 46, 8. 6. 47, 31. 5. 48 and 27. 5. 49, from several places: E. A. J. - Rova- niemi, Saarenkylä, 31. 5. 48; E. A. J. Tervola, 1. 6. 46, from several places: E. A. J. Yli- tornio, 25. 5. 48; L. Massa. - • 1 5 i 1 Abbreviations of the plant geographical countries in the list are the following: Sa = Savoina australis, Oa = Ostrobottnia australis, Sb = Savonia borealis, Kb = Karelia borealis, Om = Ostro- bottnia media, Ob = Ostrobottnia borealis, Lk Lapponia kemensis. 2 Observed in the experiment of Pohjakallio (cf. p. 131) OVERWINTERING OF GRAMINEAE-PLANTS AND PARASITIC FUNGI 131 Pk. Kolari, Venejärvi, 7.6. 46; J. Juppila; Kolari, Nuottajoki, 10.6. 48: E. Ajanti; Kolari Vaattajärvi, 25, 4. 48; V. Kortelainen. Pelkosetmiemi, 25.5. 48; M. Unkuri. Poa pratensis L. Ob. Rovaniemi, Apukka, Exp. Sta., 26.5. 49: E. A. J. P. serotina Ehrh. Ob. Rovaniemi, Apukka, Exp. Sta., 31.5. 48 1 and 27.5.49; E. A. J. P. trivialis L. Ob. Rovaniemi, Apukka, Exp. Sta., 27.5. 49: E. A. J. Secale cereale L., winter rye. Sa. Mikkeli. Karila, Exp. Sta.. 10.6.46: H. Ekstrand; 29.4.48: Y. K. Koskinen. Oa. Ylistaro, Exp. Sta., 5.6. 46; E. A. J. Om. Revonlahti, Ruukki, Exp. Sta., 4.6. 46: E. A. J. Sb. Maaninka, Exp. Sta, 8.6. 46: H. Ekstrand; 4.6. 47; E. A. J. Kb. Pielisensuu, Mustola, 2.6. 47; E. A. J. - Tohmajärvi, Exp. Sta., 7.6. 46 and 3.6. 47, from peat soil and mineral soil; Tohmajärvi, church village, 7. 6. 46 and 3. 6. 47; E. A. J. Ob. Town Kemi, 13. 5. 46, Kemi, Pattola, 1. 6. 46; E. A. J. Kemijärvi, Joutsijärvi, 1. 6. 48, from different places: E. A. J. Kuivaniemi, Kauppi, 30. 4. 48; A. Halttu. Rovaniemi, Apukka, Exp. Sta., 2. 6. 46, 8. 6. 47, 31. 5. 48 and 26. 5. 49; E. A. J. Simo, Simonkylä, 2. 5. 48; O. Salmela. .Ylitornio, 25.5. 48: L. Massa. Tervola, 1.6. 46, from different places; E. A. J. Lk. Kolari, Sieppijärvi in Midsummer rye, 7.6.46; J. Juppala, Kolari, Vaattajärvi, 25.4.48; V. Kortelainen. Triticum sativum Lam., winter wheat. Ob. Rovaniemi, Apukka, Exp. Sta., 7. 6. 47 ja 31. 5. 48: E. A. J. Detailed observations on the occurrence of S. borealis in Finland were made by the author on visits to agricultural experiment stations in springs 1946—49. These are recorded in the following. At the Perä-Pohjola Agricultural Experiment Station in Apukka (located near Rovaniemi in the arctic circle) some varieties of winter cereals were badly thinned by S. borealis in spring 1946 (cf. p. 134). Also in the timothy fields of 2nd and 3rd year damages were considerable; 20—30 % of the vegetation had disappeared because of the fungus. On the farm tillages of the Station, fungus was also met in Greus rye which in the variety experiments had remained uninfected. In 1947 the losses were smaller than in the preceding year. Winter wheat (Olympia) was entirely destroyed by snow mould and S. borealis, the share of the latter amounting to 20—30 %. In 1948 losses caused by 5. borealis were only insignificant in the variety experiment of winter rye and slight in the Olympia winter wheat. An experiment arranged by Pohjakallio with different grass species in order to elucidate the significance of photoperiodism was damaged by S. borealis especially in regard to timothy. In the spring immediately after melting of snow it seemed as if the growth of timothy were completely checked. Later, in the beginning of June timothy had, however, grown stronger, though remained thin. In 1949 the amount of S. borealis met with in winter rye and grass tillages was next to nothing. On the other hand, a great deal of the fungus appeared in the grass experiment arranged at the Station (cf. p. 133). 1 Observed in the experiment of Pohjakallio (cf. above). F. TAM ALAINEN132 At the Pohjois-Pohjanmaa Agricultural Experiment Station in Ruukki (abt. 45 km. south-west of the town Oulu) and at the Etelä-Pohjanmaa Agricultural Experiment Station in Ylistaro (abt. 50 km. east of the town Vaasa) the fungus was met in a small degree only in 1946. In 1947 and 1949 no detailed reports on the fungus were received from these stations and in 1948 it did not occur at all. In the Pohjois-Savo Agricultural Experiment Station at Maaninka (abt. 45km. north-west of the town Kuopio) S. borealis had according to the reports of Ekstrand (cf. 7,9, 10, 11) caused considerable damage on peat soil in the first-year timothy fields (abt. 50 % of the vegetation had suffered) and in winter rye, also in the Vjatka-variety, on the average 20 %of the plants were destroyed. In the fields on mineral soil the damages, again, were slight. The fungus caused plenty of damage in the neighbourhood of the Station in spring 1946. On account of it the hay yield was commonly poor from the Ist year fields on peat soil (according to Mr. M. Salminen in the annual report of the Station). In 1947 S. borealis occurred abund- antly in the Ist year timothy fields on mineral soils destroying the lower leaves of timothy. Growth was luxuriant and no actual losses were caused by the fungus. The field was in good growing condition. In one field of winter rye on peat soil near the Station the fungus had completely ruined an area of about 3—4 ares. The field was on virgin soil, only slightly fertilized. In 1948 the fungus was met on the Station in the English rye-grass only. In the neighbourhood of the field where 5. borealis had entirely killed the plants in the preceding year, no fungus was met in the rye. In 1949 slight damages by the fungus were discovered exclusively in Ist year timothy fields on peat soil. At the Experiment Station of the Peat Culture Society, at Tohmajärvi (abt. 60 km. south-east of the town Joensuu) S. borealis was abundantly met in winter rye on peat soils in 1946. In the fertilization experiment about 60—70 %of the crops from plots given the basal fertilization were destroyed by S. borealis, snow mould (Fusarium nivale) and Typkula spp. In the plots fertilized with potassium and phosphates 10—20 % of the plants were damaged by fungi. On the mineral-soils of the Station S. borealis was rare. In spring 1947 S. borealis had not caused any marked losses at the Tohmajärvi Experiment Station. In spring 1948 S. borealis was met at the Station only in one single place in a timothy field on humus sand soil, and in 1949 it did not occur at all. At the Etelä-Savo x\gricultural Experiment Station in Karila near the town Mikkeli, Ekstrand noted (7, p. 50) in spring 1946 considerable injury caused by the fungus in Ensi-rye on peat soil. In the fields on mineral soil the fungus was in- significant. In 1948 a sample of the plants of winter rye was received from the Station showing contamination by 5. borealis. Information about the appearance of S. borealis has been obtained, besides from experiment stations, also from other places on the basis of the author’s observations and of the samples sent to the Department of Plant Pathology. The information obtained is presented on pp. 130—131. The above reports on S. borealis from four years show that the fungus is in Finland as well as in Sweden a species occurring in the middle and northern parts of the country. On the basis of the information so far obtained it can be concluded that the fungus is more or less common in years favourable to its oc- currence in the provinces of Lapland, Oulu, Kuopio and Mik- keli. What the significance of the fungus in other parts of the country is, cannot be decided for certain by the information available. In the author’s opi- nion it may not be a cause of any greater damage in the south and south-western Finland. In estimating the losses cau- sed by the fungus it must be taken into account that they vary greatly in different years and even in the same year in different places. When occurring slightly, the fungus destroys a few percentages of the plants. There are either small bare pla- ces in the fields or the indivi- dual plants or their lower leaves are injured, as for instance at Maaninka in 1947 (see p. 132). In such cases the damages are of no greater bearing, because as the growth ad- vances the gaps will be filled in and not even noticed later in summer. When fungus makes larger areas bare (fig. 2) and these are met frequently, or when the borders of the field plots are damaged by the fungus, the losses occurred may rise high, 10—30 % of the crop may be lost. In the worst case the fungus may des- troy large areas, several ares. The disappearance of timothy and other valuable grass species from many-year grass fields in the northern parts in Finland as well as in Sweden may often result from 5. borealis (cf. Fig. 4). On the resistance of Gramineae-plants to Sclerotinia borealis. Occurrence of S. borealis has been noted, besides in the winter rye, wheat, and timothy reported in the preceding chapters, also in the following Gramineae- plants 1 : Agrostis canina L., A. stolonijera L., A. tenuis Sibth. (2. p. 12), Alo- -1 When no reference to literature is made of a species, the fungus has been observed in Fin- *and, cf. p. 130 131. Fig. 4. Timothy damaged by Sclerotinia borealis in former years. Photograph in spring 1948 from an unfer- tilized plot in a fertilizing experiment. Place of experiment Sahavaara, Kaunisvaara, Sweden. Photy by E. A. Jumalainen. Kuva 4. Sclerotinia borealis en aikaisempina vuo- sina hävittämää timoteinurmea. Valokuvattu kevällä 1948 lannoituskokeen lannoittamattomasta ruudusta. Koepaikka Sahavaara, Kaunisvaara, Ruotsi. 133OVERWINTERING OF GRAMINEAE-PLANTS AND PARASITIC FUNGI E. A. JAMALAINEN134 pecurus pratensis L., Anthoxanthnm odoratum L., Bromus mermis Leyss., Dactylis glomerata L. (2, p. 12), Festuca pratensis Huds. (8, p. 72), F. rubra L. (2, p. 12), Loliuni perenne L. (2, p. 11), Poa annua L. (2, p. 11), P. pratensis L. (2, p. 12), P. serotina Ehrh. (2, p. 12) and P. trivialis L. h Ulander (17, 18, 19) and later Nilsson and Naesman (15) and Ekstrand (2, 8,9, 11 etc.) in Sweden emphasize that the resistance of winter rye varieties and field grasses to parasitic winter fungi is largely dependent on the fact where the plant has been grown. The varieties and strains grown in the north are more resistant to these fungi than those grown in the south. This holds true, according to Ekstrand, also of S. borealis. Different varieties of winter cereals are, according to the findings of Ekstrand (11) during several years, approximately as resistant to S. borealis as to Fusarium and Typhula spp. Consequently, the varieties of winter cereals can be divided into two groups. Those resistant to parasitic winter fungi are the Finnish varieties Ensi, Oiva, and Toivo and of the other varieties Sangaste, Björn, and a number of country varieties, first of all the ryes of Norrland and the Midsummer ryes. Varieties susceptible to winter fungi are inter Improved Vaasa 11, Stål, Kungs, Malm, Petkus, and some improved varieties of Svalöv. The Finnish reports on the resistance of rye varieties to S. borealis date from 1946 when the fungus occurred abundantly at the Perä-Pohjola Experiment Station in Apukka (cf. p. 131). The density of the plants of different winter rye varieties was in the variety experiment in spring the following: Onni abt. 20 %, Oiva 20— 25 %, Toivo 40—50 %, Ensi 75 %, and Greus (country variety) 95—ICO %. The damages were mainly caused by S. borealis. According to the observations made by the author Ensi-rye is almost entirely free from S. borealis or only slightly damaged when grown as Midsummer rye. The winter wheat is according to Ekstrand (10, p. 24) more susceptible to S. borealis than rye. Differences are noted between different varieties, though not great. The observations in Sweden show that the resistance to S. borealis of different strains of timothy is very variable. Such strains of timothy which have been deve- loped in South Sweden are more susceptible to the fungus than the northern strains (8, p. 72). The Bottnia timothy has proved to be well resistant to S. borealis (15, p. 33). The resistance of other field grass strains is according to Ekstrand (8, p. 72; 10, p. 24—32) also very variable in regard to S. borealis, for example the northern strains of Festuca pratensis and F. rubra are more resistant than the southern strains. Of the other field grasses in Sweden, except timothy, the 1 Ulander (17, p. 47—-48) found sclerotia-forming fungi in North Sweden in the following field grasses: Alopecurus nigricans, A. pratensis, Avena elatior, Dactylis glotnerata, Festuca ovina, F. pratensis , F. rubra, Phleum pratense, Poa alpina, P. Chaixii, P. pratensis, P. serotina, P. sudetica and P. trivialis. He assumed that one or two species of fungi were concerned and states later (19, p, 241—242) that they were S. borealis and Typhnla. following are susceptible to S. borealis: Dactylis glomerata (19, p. 239—241), Lol- ium perenne (cf. Fig. 5) and Poa praten- sis (10, p. 26). Department of Plant Pathology ar- ranged an experiment in 1948 at the Perä- Pohjola Experiment Station in Apukka (cf. p. 131), in which the susceptibility of se- veral grass species and strains to S. borea- lis was examined. The seeds were sown in mid-July, the plots were small, every plot contained 40—60 plants, the number of parallel plots was four. Results of the experiment are presented in Table 2. In spring, May 26—27, the experiments were analyzed, i.e. the healthy plants and those damaged by the fungi were counted. The plants started their overwintering being fragile in growth, since the seeds had been sown only in the middle of the sum- mer. For this reason, apparently, great amounts of S. borealis appeared in the test plants. As was mentioned before (p. 131), the amount of fungus observed in spring 1949 in other grass tillages of the Experiment Station was next to nothing. In the experiment, S. borealis appeared most strongly in Poa serotina, P. trivi- alis, Dactylis glomerata, Pbleum pratense, Festuca rubra and Folium perenne. Great differences were observed between the different strains. Bottnia-timothy was almost entirely free from the disease. The timothy strain Lappi and Tarmo were also fairly well resistant to S. borealis. The appearance of fungus was strong in those samples, where the seed was of North American origin. The Finnish Festuca rubra strain was only slightly infected whereas in the Swedish strain the disease was comparatively plentiful. As was mentioned above, Dactylis glomerata is known to be susceptible to S. borealis. In our experiment, the Gullåker and Danish Trifo- lium strain showed S. borealis to a greater extent. In the experiments, Folium perenne strains were very much infected. More resistant to S. borealis than the above-mentioned grass species were Alopecurus pratensis, Anthoxanthum odoratum, Agrostis canina and A. stolonifera, in which there were 5—6 % cliseased plants. The Agrostis tennis, Poa pratensis and Festuca pratensis strains were either totally free from the disease or only slightly infected. As is seen in Table 2, the Agrostis species germinated badly, so the observation material on their part remains small. S. borealis had in most cases entirely damaged the plants it had infected. The Fig. 5. English rye-grass damaged by Scle- rotinia borealis. Photographed in spring 1948 at Porsögården, Branch Station of the Swedish Seed Association near Boden. Photo by E. A. Jumalainen. Kuva 5. Sclerotinia borealisen turmelema eng- lantilainen raiheinä. Valokuvattu keväällä 1948 Ruotsin kylvösiemenyhdistyksen haara- osastossa Porsögärdenissa lähellä Bodenia. 135OVERWINTERING OF GRAMINEAE-PLANTS AND PARASITIC FUNGI Table 2. Grass experiment at Perä-Pohjola Taul. 2. Nurmiheinäkoe Perä-Pohjolan In brackets separately the percentage of injuries] Sulkeissa erikseen se osa saastuneista yksi- Density of Total number Plants inju- _ , . , , growth in of plants in red by S.Grass species and strains b . , Q/r autumn 1948 spring borealis % o—lo Kasvuston Yksilöitä 5. borealisen Heinälajit jakannat tiheys syk- keväällä turmelemia syliä o—-100—-10 yhteensä yksilöitä % Agrostis canina, koiranrölli 0.5 20 5 A. stolonifera, rönsyrölli 4.6 68 6 A. tenuis, nurmirölli 3.6 49 0 Alopecurus pratensis, nurmipuntarpää Weihenstephan, Germany 8.3 220 4 (1.5) A 660, Tammisto, Finlard 7.1 168 6 Anthoxanthum odoralum, tuoksusimake . . 6.8 108 6.5 Dactylis glomerata, koiranruoho Gulläker, Sweden 9.1 166 20 (5) Jo D 70, Jokioinen, Finland 6.8 87 9 Tammisto 11, Finland 8.3 141 6 Trifolium, Denmark 9.8 148 21 (12) Festuca pratensis, nurminata Bottnia, Sweden 9.6 231 1.5 Paavo, Jokioinen, Finlard 9.6 237 O Svalöf, late (myöh.), Sweden 9.9 215 2.5 Tammisto 11, Finland 9.4 215 1 otofte I, Denmark 9.9 224 n F. rubra, aronata Reptans, Sweden 9.3 229 20 (20) Tammisto 11, Finland 8.8 248 2 Lolium perenne, engl. raiheinä Valinge, Sweden 9.5 239 11.5 Viktoria, Sweden 9.3 199 20.5 (4) otofte I, late (myöh.), Denmark .... 8.4 205 18 (5) cases in which part of the plants were saved from the disease are mentioned sepa rately in the table. In the experiment, besides S. borealis, also damages by Typhula spp. fung took place but they were not defined according to species. Mostly they occurrec in Trifolium timothy, Poa serotina, in Weihenstephan Alopecurus pratensis strait and in Agrostis species. In some grass species the green parts of the plant; were either totally destroyed or part of the leaves were destroyed, although nc fungi were to be observed in them at the moment the observations were made. It these instances, it was obviously a case of snow mould; the leaves of the plant; 136 E. A. JAM ALAINEN OVERWINTERING OF GRAMINEAE-PLANTS AND PARASITIC FUNGI 137 Experiment Station in Apukka in 1948—4g. koeasemalla Apukassa vv. 1948—49. plantshat were only partly damaged by fungus Loista, jotka vain osittain sienen turmelemia. Density of Total number Plants inju- Grass species and strains growth in of plants in red by S autumn 1948 spring borealis % o—lo Kasvuston Yksilöitä S. borealisen Heinälajit ja kannat tiheys syk- keväällä turmelemia syliä o—-100—-10 yhteensä yksilöitä % I‘hleum pratense, timotei Bottnia, Sweden 9.3 161 1 Gloria, Sweden 8.4 173 11 Lappi Tl., Finland 8.1 168 2.5 Omnia, Sweden 9.3 187 16.5 Tammiston timotei (Tammisto timo- thy), Finland 7.3 162 16.5 Ta 01, Tammisto, Finland 5.6 153 8 Tarmo, Jokioinen, Finland 7.1 173 6 Trifolium, Denmark 6.8 132 10 Vanadis, Sweden 8.6 148 38.5 Otofte, Denmark 9.0 181 8.5 Exp. series (koe-erä) No. 5, of Canadian origin (Kanadasta) 2.6 80 16.5 No. 2650, —6.4 99 54.5 No. 4, —5.0 107 31 No. 554, —6.3 130 23 Poa pratensis, niittynurmikka Adila, Esthonia 9.9 280 2 Gullåker, Sweden 9.9 253 0 Exp. series (koe-erä) No. 62, of foreign origin (ulkol. alkuperä) 9.6 224 2 l’oa serotina, rantanurmikka Hammenhög, Sweden 9.4 179 40 Primus, Sweden 9.9 172 29 P. trivialis, aronurmikka 9.5 254 20 (6) were destroyed in a manner typical of snow mould (cf. p. 128). This w'as observed in Agrostis tennis , Festuca pratensis, F. rubra and in some strains of Dactylis glomerata. It was shown in the above that some winter rye varieties developed in the north, in particular the Finnish ones, seem to be fairly resistant to the disease. As regards timothy and other field grasses, the information so far available likewise reveals that the varieties most resistant to 5. borealis are to be found in the districts where the fungus occurs. It is not worth while to grow grass species and their 138 E. A. JAMALAINEN strains susceptible to the fungus in regions where S. borealis occurs. In the breeding work it is essential to use material derived from the northern parts of the country and resistant both to 5. borealis and other parasitic winter fungi. Also testing of the varities must be performed in conditions where these fungi are abundant. On the control of Sclerotinia borealis. In the control of the fungus chief attention must be paid to the growing of resistant varieties of winter cereals and grass strains, as pointed out in the foregoing. In addition, even some other measures must be considered in order to prevent losses by 5. borealis. Reports on S. borealis show that the plant nutrients of the soil have an effect on its more or less abundant occurrence. Ekstrand (7, 9, 10, 13), draws attention to this question on the basis of his observations on the fertilizing experiments. In 1942 he found (10, p. 38) in Swedish experiment that in the unlimed plots the timothy was more infected by S. borealis than in the limed ones. Both lime and phosphate were used in the experiment. Lime was then no direct cause for the less abundant occurrence of the fungus, it had evidently set free mobilized phosphoric acid which was necessary for increasing the resistance of timothy. In Finland, at the Tohmajärvi Experiment Station, Ekstrand and the author noted in 1946 that in the experiment with winter rye more plants were destroyed by S. borealis and snow mould in unlimed plots than in plots given both lime and phosphate. Lnder these circumstances for the control of S. borealis the fields must be in good growing condition and the plants must be given in particular phosphate fertilizers that seem to increase their resistance both to S. borealis and other parasitic winter fungi. 6 The other measures for the control of the disease are the same as those for the control of snow mould. An early harrowing is made in the spring and the dead leaves are gathered and burnt. Melting of snow drifts is forced by sprinkling ash or mould on them. To strengthen their growth the plants must be given nitrate. If it seems that the vegetation is entirely damaged, it is best to plough the field up. This should, however, be carefully considered, because as was mentioned above (p. 131) the plants impaired by the fungus do not always die altogether, but will revive in the spring when a satisfactory crop can be expected. S ummar v. In the middle and northern parts of Sweden and Finland Gramineae-planti are infected by a fungus of Sclerotinia-genus which causes injury during the overwintering of the plants. Vleugel in Sweden described the fungus with the name Sclerotinia borealis Bubåk and Vleugel in 1917. OVERWINTERING OF GRAMINEAE-PLANTS AND PARASITIC FUNGI 139 In Sweden S. borealis has been met in several years causing injury to winter rye, timothy, cocksfoot and other field grasses. It occurs commonly in Norrland, especiclly in the country Norrbotten. The southern limit of its spreading area in Sweden is in latitude about 61° N. In Finland S. borealis is met in the middle and northern parts of the country. On the basis of the information hitherto the fungus is more or less general in the years favourable to its occurrence in the provinces of Lrpland, Oulu, Kuopio and Mikkeli. When occurring more abundantly as happened during the overwintering 1945—46, S. borealis is in these regions one cause for the poor overwintering of winter rye, timothy and other grasses. The climatical conditions prevailing during autumn, winter and spring are of decisive bearing for the spreading of S. borealis as well as for its abundant occur- rence in certain years. The development of the apothecia of the fungus and the spreading of the ascospores is evidently favoured by long, rainy autumn, the dama- ges are promoted by low freezing of the soil and thick cover of snow in the winter as well as by slow melting of snow in the spring. Of the occurrence of 5. borealis in different Grammeae-plants, see p. 133—134. Different varieties of winter cereals and species and strains of grasses vary greatly in resistance to S. borealis. It has been observed that, of the varieties of winter rye, especially the Finnish ones resist the disease caused by the fungus very well. Of field grasses, Phleum pratense, Dactylis glomerata, Lolhim perenne, Poa serotina, and P. trivialis are susceptible to S. borealis. Some strains of these species, however, are extremely well resistant to the fungus. The strains of the grasses and varieties of winter rye grown in the north are generally more resistant to the damages by the fungus. In developing new varieties of winter cereals and strains of field grasses for the northern conditions these facts must be duly considered and for the breeding w'ork such material should be selected which has grown in the district where the fungus occurs. Obviously the damages caused by the fungus are less when the plants receive plenty of nutrients, especially phosphates whereby they become stronger to resist infections. REFERENCES (1) Ekstrand, H. 1937. Sklerotiesjuka på fodergräs. Växtskyddsnotiser, 1. årg., p. 4—5. (2) —»— 1939, Några ekonomiskt viktiga sjukdomar på höstsäd och vallväxter. With German Summary. Statens Växtskyddsanstalts Meddelande, 25, p. I—-23. (3) —,) — 1940. Skadorna på höstsäden under vintem 1939—40. Växtskyddsnotiser, 4. årg., p 33—38. (4) —»— 1942. Årets vinterskador på höstsäd och vallar. Ibid. 6. årg., p. 38—42. (.5) —»—- 1946. Höstsäden och vinterhärdighetsproblemet. Ibid. 10. årg., N;r 1, p. 15—16, N:r 2 p. 17—21. (6) —.»—. 1946. Höstsädens och vallamas övervintring 1945—46. Ibid., 10. årg., p. 44—48. (7) —o ■ 1946. Förekomsten av utvintringsvampar på höstsäd och vallväxter i Finland. Ibid. 10. årg., p. 49—55. (8) —1946. Några växtpatologiska synpunkter på höstsädes-och vallodlingen i Norrland. Ibid. 10. årg., p. 68—73. (9) —*—• 1947. Eräitä kasvipatologisia näkökohtia syysviljojen ja nurmiheinien talvehtimisesta. With Swedish Summary. Journ. Sei. Agr. Soc. Finland, 19. p. 39—59. (10) —*— 1947. Några växtpatologiska synpunkter på övervintringen av höstsäd och vallgräs med särskild hänsyn till försökverksamheten inom jordbruket. With English Summary. Sta- tens Växtskyddsanstalts Meddelande, 49, p. I—4B. 11) —»— 1947. Höstsäden och vinterhärdighetsproblemet med särskild hänsyn till resistensen mot vissa svampsjukdomar. With English Summary. Ibid., 50, I—2B. (12) —»— 1948. Skadorna på de övervintrande grödorna vintem 1947—48. Växtskyddsnotiser, 12. årg., p. 70—75. (13) —»— 1949. Näringsförhållandena och vallgräsens övervintring. Ibid., 13. årg., N;r 2, p. 5—9 (14) Jamalainen, E. A. 1947. Talvehtimissienien merkityksestä kasvinviljelyssä. Maatalous, 40, p 156—161. Finnish. (15) Nilsson, F. & Naesman, F. 1937. Några försöks- och förädlingsresultat från Sveriges Utsädes- förenings Övre-Norrlandsfilial 1920—1935. Sv. Utsädesför. Tidskr., 47, p. 20—49, 104— 130. (16) Solkina, A. F. (CoJibKHHa, A. dt.) 1939. K iisynemiio puima paaBHTMH rpnsa Sclerotinia graminearum Elen. With English Summary. Samirra paCTennii (Plant Protection), 18, p. ICO—IOB. (17) Ulander, A. 1910. Redogörelse för verksamheten vid Sveriges Utsädesförenings Filial i Luleå år 1906—4909. Sv. Utsädesför. Tidskr., 20, p. 33—53. (18) —»— 1914. Redogörelse för värksamheten vid Sveriges Utsädesförenings Filial i Luleå år 1913. Ibid., 24, p. 260 —281. (19) —>— 1915. Ett och annat från verksamheten vid Sveriges Utsädesförenings Luleå-Filial. Ibid,, 25. p. 231—243. (20) Valle, Otto 1931. Untersuchungen über die Selbststerilität und Selbstfertilität des Timothes [Phleum pratense L.) und über die Einwirkung der Selbstbefruchtung auf die Nachkom- menschaft. Acta Agralia Fennica, 24, p. 1—262. (21) Vleugel, J. 1917. Zur Kenntnis der Pilzflora in der Umgegend von Umeå und Luleå. 111. Sv. Bot. Tidskr. 11, p. 304—324. SELOSTUS GRAMINEAE-KASVIEN TALVEHTIMINEN JA TUHOSIENET I. SCLEROTINIA BOREALIS BUBÄK & VLEUGEL E. A. Jamalainen Maalalouskoelaitoksenkasviiautiosasto, Tikkurila. Tärkeimpiä syitä Gramineae-kasvien huomioon talvehtimiseen Suomessa ovat kasveja talvehti- misen aikana turmelevat tuhosienet, ns. talvehtimissienet. Tässä eri osina julkaistavassa tutkimuksessa tullaan tekemään selkoa, mikä merkitys talvehtimissienillä on maassamme syysviljojen ja niittyheinien viljelyssä. Ensimmäiseksi otetaan selostettavaksi Sclerotinia borealis BUBÄK & VLEUGEL, joka esiintyy vahinkojen aiheuttajana keski- ja pohjoisosissa Ruotsia ja Suomea. 140 E. A. JAMALAINEN Sienen totesi Ruotsissa ensimmäisen kerran Ulander v. 1906 Luulajan seudulla (17). Myöhem- min osoitettiin, että S. borealis on yleinen Norrlannissa, varsinkin Norrbottenin maakunnassa, jossa se useina vuosina aiheuttaa huomattavia vahinkoja syysrukiissa, timoteissa ym. nurmiheinissä (Ulander ja Ekstrand useissa tutkimuksissaan, ks. kirjallisuusluetteloa). S. borealisen esiintymisalue ulottuu Ruotsissa etelässä Taalainmaan ja Gästriklannin maakuntiin (10). Suomessa on kirjoittaja yhdessä fil.lis. H. Ekstrandin kanssa keväällä 1946 suorittamallaan mat- kalla pohjois- ja keskiosissa maata todennut 5. borealisen esiintyvän useilla seuduilla yleisenä syys- rukiissa ja timoteissa. Kolmena seuraavana vuonna on Maatalouskoelaitoksenkasvitautiosaston taholta jatkettu tutkimuksia sienen levinneisyyden ja sen aiheuttamien vahinkojen selvittämiseksi. Keväällä 1948 teki kirjoittaja yhdessä fil.lis. Ekstrandin kanssa matkan myös Pohjois-Ruotsiin, jossa suori- tettiin tutkimuksia talvehtimissienistä. Sclerotinia borealis BobÅk & VLEUGEL-sienen kuvasi Vleugel Ruotsissa v. 1917 (21). Hänen selostuksensa vastaa kirjoittajan saamaa kuvaa sienestä. Apotekioiden muoto ja suuruus (kuva 1), samoin kuin itiökoteloiden ja itiöiden koko ovat samaa suuruusluokkaa. Taulukossa 1 on esitetty lukuja sienen sklerotioiden suuruussuhteista, josta käy selville, että sienirihmapahkojen koko vaihtelee riip- puen siitä, mistä isäntäkasvista ne ovat peräisin sekä siitä tehdäänkö mittaukset kuivista vai kos- teudessa olleista sklerotioista. Paras aika S. borealisen toteamiselle on kevät, kohta lumen sulamisen jälkeen. Syysrukiin oraiden ja heinäkasvien paljastuttua lumen alta on sienen saastuttamissapelloissa suurempia tai pienempiä aloja kasvustosta tuhoutunut (kuva 2). Kirjoittajan havaintojen mukaan on taudille tyypillistä, että sienen tappamat lehdet ovat kuivettuaan enemän tai vähemmänrihmamaisia, väriltään harmaita tai harmaan- ruskeita (kuva 3). Tässä suhteessa ovat S. borealisen ja lumihomeen aiheuttajan Fusarium nivale (FR.) CES.n vahingot helposti eroitettavissa toisistaan. F. nivalen turmelemien oraiden lehdet ovat kuivettuaankin levällään ja usein hieman punertavia. S. borealisen aiheuttamatvahingot voivat kevään kuluessa lisääntyä siten, että juuri lumen sulaessa kasveja on runsaammin elossa kuin myöhemmin. Sienen heikentämät yksilöt eivät jaksa elpyä, vaan kuolevat lopuksi. Toiselta puolen voivat sienen vuoksi heikossa kunnossa olevat kasvit vielä myöhem- min vahvistua, kuten todettiin Perä-Pohjolan kasvinviljelyskoeasemalla timoteissa v. 1948. Kirjoittajan kokeiden mukaan alkoi keväällä kerättyihin S. borealisen sklerotioihin muodostua apotekioita vasta syksyllä ilmojen muututtua kylmemmiksi, syys—lokakuussa. Laboratorio-olosuh- teissa ei itiöemien muodostuminen ollut normaalia. Usein niihin kehittyi vain varsi. Apotekiot olivat selvästi valohakuisia. Tiedot S. borealisen levinneisyydestä osoittavat, että se suosii pohjoisia seutuja. Tästä syystä täytyy näillä seuduilla vallitsevilla ilmastosuhteilla olla ratkaiseva merkitys sen esiintymiselle. Pitkä, kostea ja lämmin syksy, jolloin lumi tulee routaantumattomaan maahan, on ilmeisesti edullisin sienen leviämiselle. Edelleen voidaan päätellä, että toiselta puolen maan routaantuminen ja toiselta puolen lumikerroksen paksuus sekä sen nopeampi tai hitaampi sulaminen vaikuttavat sienen tuhojen suuruu- teen keväällä, Jos maa on matalaan routaantunut ja lumikerros on paksu, samalla kun lumi sulaa keväällä hitaasti, on sienellä suuret mahdollisuudet tehdä vahinkoja. Niiden neljän vuoden aikana, jolloin kirjoittaja on kerännyt tietoja S. borealisesta, olivat sen vahin- got suurimmat ja esiintymisalue laajin keväällä 1946. Kolmena seuraavana keväänä tavattiin sientä huomattavasti vähemmän; vv. 1948 ja 1949 sitä esiintyi suoranaisten vahinkojen aiheuttajana vain Perä-Pohjolan koeasemalla lähellä Rovaniemeä. Mistä tämä johtuu on vaikeata varmemmin päätellä saatavissa olleiden sää-, lumisuus- ja maan routaantumistietojen perusteella. Kysymyksen selvittely edellyttää lämpötila-, lumisuus- ym. tutkimuksia sienen esiintymispaikoissa. Sivuilla 130—-131 luetellaan Maatalouskoelaitoksen kasvitautiosastolle kerääntynyt aineisto sienestä ja sen esiintymispaikoista. Yksityiskohtaisia tutkimuksia S. borealisen esiintymisestä on kir- joittaja tehnyt koeasemille keväisin vv 1946—49 suorittamillaan matkoilla. Neljän vuoden aikana saadut tiedot S. borealisesta osoittavat, että sieni on Suomessa kuten Ruot- sissakin maan keski- ja pohjoisosissa esiintyvä laji. Valle (20) totesi Tammistossa (Hankkijan kasvin- jalostuslaitos Malmilla) timoteissa keväällä 1930 tuhoja, joita hän pitää S. borealisen aiheuttamina. Sienen vahinkoja esiintyi Tammistossa paitsi timoteissa myös koiranruohossa v. 1927. Eteläisin paikka, Etelä-Savon koeasema, josta kirjoittaja on saanut näytteen sienestä, sijaitsee lähellä Mikkeliä. Tähän- 141OVERWINTERING OF GRAMINEAE-PLANTS AND PARASITIC FUNGI 142 E. A. JAMALAINEN astisten tietojen mukaan tavataan sientä enemmän tai vähemmän yleisenä sen esiintymiselle edullisina vuosina Lapin, Oulun, Kuopion ja Mikkelin lääneissä. Mikä merkitys sienellä on muissa osissa maata, ei nykyisten tietojen mukaan voida lähemmin päätellä. Jos tauti esiintyy lievänä, turmeltuu sen vuoksi vain muutamia prosentteja kasvustosta, joko siten, että pellossa on pieniä aukkokohtia, joissa kasvit ovat tuhoutuneet, tai ovat yksityiset kasvit taikka niiden alemmat lehdet turmeltuneet. Tällaisissa tapauksissa ei vahingoilla ole suurta merkitystä, sillä kasvun edistyessä aukkokohdat täyttyvät, eikä niitä myöhemmin kesällä edes enää huomata. Sel- laisissa tapauksissa, jolloin sieni synnyttää suurempia aukkokohtia ja niitä tavataan runsaasti (kuva 2) tai peltosarkojen reunat ovat sienen turmelemia, voi taudista johtuva vahinko olla huomattava, 10—30 % sadosta voi mennä hukkaan. Pahimmissa tapauksissa tuhoaa sieni suuria, yhtenäisiä useampien aarien suuruisia aloja. Timotein ja muiden arvokkaiden heinälajien häviäminen useampivuotisista nurmista pohjoisissa osissa maatamme samoin kuin Ruotsissa, voi täten olla monissa tapauksissa S. borealisen aiheuttamaa (vrt. kuva 4). Tähänastisten tietojen mukaan on S. borealis, sen esiintymiselle edullisina vuosina yhtenä syynä syysrukiin ja nurmiheinien huonoon talvehtimiseen pohjois- ja keski-itäosissa maatamme. S. borealis esiintyy paitsi syysviljoissa myös useissa heinäkasveissa, jotka on lueteltu siv. 133—134. Eri syysviljalajikkeiden ja nurmiheinälajien sekä niiden kantojen kestävyydessä S. borealista, vastaan on huomattavia eroavaisuuksia. On todettu, että syysruislajikkeista varsinkin suomalaiset ovat kestä- viä sienen aiheuttamaa tautia vastaan (vrt. Ekstrand, 11). Sellaisia ovat tähänastisten tietojen mukaan lajikkeet Ensi, Toivo Greus (maatiaislajike) ja maassamme kokeiltavana ollut venäläinen lajike Vjatka. Muista rukiista on Ruotsissa todettu kestäviksi lumihometta, 5. borealista ja Typhula spp.-sieniä vas- taan Björn- ja Sangaste-rukiit, eräät ruotsalaiset maatiaislajikkeet sekä juhannusruis. Nurmiheinistä ovat timotei, koiranruoho, engl. raiheinä, rantanurmikka ja aronurmikkaalttiita S.borealiselle. Eräät näiden lajien kannat ovat kuitenkin sienen suhteen hyvin kestäviä, kuten Ruotsissa tehdyt havainnot ja Suomessa Perä-Pohjolan koeasemalla suoritetut kokeet osoittavat (taul. 2). Sienen esiintymispaikoilla kehittyneet syysviljalajikkeet ja heinäkannat, ovat kestävämpiä S. borealista vastaan kuin muualta saadut (Ulander, 17, 18, 19; Nilsson & Naessman, 15; Ekstrand, 2. 8,9, 11). Kehitettäessä uusia syysviljalajikkeita ja nurmiheinäkantoja pohjoisia olosuhteita varten on tämä otettava huomioon ja käytettävä jalostuksessa sienen esiintymisalueella kasvanutta aineistoa, samoin kuin jalostusmateriaali on kokeiltava seuduilla, joissa sientä esiintyy. Sienen torjunnassa on kiinnitettävä ensisijainen huomio kestävien syysviljalajikkeiden ja hemä- kantojen viljelemiseen. Tämän lisäksi ovat eräät muutkin keinot varteenotettavia S. borealisenaiheutta- mien vahinkojen ehkäisemiseksi. Peltojen on oltava hyvässä kasvukunnossa ja kasveille on varattava varsinkin fosforilannoitteita, jotka näyttävät lisäävän kasvien kestävyyttä sekä S. borealista että muita talvehtimissieniä vastaan niiden toteamuksien mukaan, joita Ruotsissa ja Suomessa on tehty lannoitus- kokeista (vrt. Ekstrand, 7,9, 10, 13). Taudin muista ehkäisykeinoista tulevat kysymykseen samat menetelmät kuin lumihomeen tor- junnassa. Keväällä suoritetaan varhainenäestys, jolloin kuolleet lehdetkerätään japoltetaan. Hankien sulamista joudutetaan kylvämällä niille tuhkaa tai multaa. Kasvun vahvistamiseksi annetaan oraille salpietaria. Jos näyttää siltä, ettäkasvusto onkokonaan turmeltunutta, on syytä suorittaapellon nurin- kyntö. Tätä on kuitenkin tarkoin harkittava, sillä sienen heikentämät kasvit eivät aina kuole kokonaan, vaan saattavat elpyä myöhemmin keväällä.