EXPERIMENTS ON THE USE OF SOME CHLORONITROBENZENE AND ORGANIC MERCURY COMPOUNDS FOR THE CONTROL OF LOW-TEMPERATURE PARASITIC FUNGI ON WINTER CEREALS E. A. Jamalainen Department of Plant Pathology, Agricultural Research Centre, Tikkurila Received September 12. 1958. Studies have been made at the Department of Plant Pathology of the Agri- cultural Research Centre on the possibilities of controlling damage from parasitic fungi in dormant plants by treating stands with fungicides in the autumn, shortly before the fall of snow. The results of the experiments carried out before the winter 1955—56 were published in 1956 as Publications of the Finnish State Agricultural Research Board No. 148— »Overwintering of plants and experiments on the chemi- cal control of low-temperature parasitic fungi in Finland» (cf. 3,6). The following gives an account of the results of experiments on winter cereals carried out in 1955—1958. The weather conditions during the winters 1955—1958 The winter of 1955—56 was very snowy. In south Uusimaa (central part of South Finland), where most of the experiments were carried out, there were excep- tionally heavy injuries from parasitic fungi on winter cereals. The damage from snow mould [Fusarium nivale (Fr.) Ces.] in particular was heavy, but the Typhula fungi, T. itoana Imai and T. idahoensis Remsb., also proved injurious. According to information collected by the Department of Plant Pathology, injuries from fungi were also heavy in the central, eastern and northern parts of Finland. In South-West Finland the damage appeared to be comparatively slight, as usual. https://www.c-info.fi/en/info/?token=YWJ7xpl6cc6y1Zer.FtgWwCtXUROl_-uPhxTEDQ.en2AXT3xrg4qxgUvoOaB93OhsbPUxIS0CrhyOCOtM_44H1JTuCg6B_XaUWJBI7Msv3FT0P3EKB-71B9mmuMsQeFM2ekHv8OYh5aJT0FJSIrhm4CYfmaniWFPNSSujPw6_OnWuaO57WVClk6ME6IZxbw7GCGxuu8iRCXkw4f1 252 The overwintering conditions for crops in the winter 1956—57 were very different from those of the previous winter (4). The soil had frozen in late autumn before the snow fell; in South Finland the soil was depht frozen. Later in the winter the weather was so warm that rain fell, covering the fields with water. The surface of the soil became waterlogged, and the frost that followed froze the water often forming a continuous surface of ice. In 1956—57 there appeared hardly any injuries from low-temperature parasitic fungi in the winter cereals in the southern part of the country. Damage from low-temperature parasitic fungi appeared in the central and northern parts of the country, although to a lesser extent than usual owing to the fact that the soil had been throughly frozen by the time the snow fell. Compared to the two preceding years the winter 1957—58 was, in Finnish weather conditions, normal for the overwintering of winter cereals. The ground was almost everywhere frozen before snowfall. Snow fell comparatively abundantly, remaining on the ground all the winter through. Damage caused by water and frost did not appear in the winter cereals to any notable degree. On the other hand low- temperature parasitic fungi (Fusarium nivale on winter rye and both F. nivale and Typhula sp. fungi on winter wheat) had caused considerable damage in snowy places ewerywhere in the country. Experiments with winter cereals Earlier experiments carried out in different countries on the chemical control of low-temperature parasitic fungi in winter cereals by a treatment of seedlings in autumn have been more detailed reported in a publication of the author in 1956 (3, p. 18—19). As to the latest studies in this field reference is made to Sprague’s experiments (9) in the State of Washington, U.S.A.; these did not lead to any posi- tive results in the control of low-temperature parasitic fungi in winter wheat in 1955—1956. Regarding the experiments in the following year, Sprague reports that positive results were obtained by using organic mercury compounds (10; cp. also 8). In the mountainous regions of West Germany good results have been obtained in the control of snow mould (Fusarium nivale) in winter rye by the use of the spray Brassicol-super, a PCNB preparation (7, 11). Chemicals used in the tests Preparation Active Appli- Amount per hectare Manufacturer ingredient cation 1 of prepa- active ration ingredient A m a t i n- HCNB-hexachloro- dust 25 kg 5 kg Farbenfabriken Staub nitrobenzene, 20 % Bayer, West Germany Avicol PCNB=pentachloro- dust 25 kg skg Rikkihappo- ja super- nitrobenzene, 20 % 50 kg 10 kg fosfaattitehtaat Oy, Vaasa, Finland Preparation Active Appli- Amount per hectare Manufacturer ingredient cation 1 of prepa- active ration ingredient Bayer 4426 PMA=phenylrnercury- dust 25 kg 125 g Farbenfabriken acetate, 0.5 % (Hg 75 g) Bayer, West Germany (Hg 0.3 %) Bo tr ilex PCNB=pentachloro- dust 25 kg 5 kg Bayer Agriculture nitrobenzene, 20 % 50 kg 10 kg Ltd., England Bras si col PCNB=pentachloro- dust 25 kg skg Hoechst A.-G., nitrobenzene, 20 % 50 kg 10 kg West Germany Dith a n e Z-78 Zineb, 65 % dust 25 kg 16.25 kg Rohm