Syysrypsin talvituhosienien torjuntakokeita käsittelemällä kasvustot fungisiideilla

Authors

• E. A. Jamalainen Kasvitautien tutkimuslaitos, Tikkurila
• Matti Haavisto Kasvitautien tutkimuslaitos, Tikkurila

DOI: https://doi.org/10.23986/afsci.71503

Abstract

In preliminary tests with winter turnip rape (Brassica campestris var. oleifera f. biennis) at the Department of Plant Pathology in 1954—1955, treatment of the stands with a PCNB (pentacholronitrobenzene) compound carried out in the autumn before snow-fall improved the overwintering by reducing the damage caused by low-temperature parasitic fungi, in particular the Typhula sp. (1). Tests in 1955—56. The winter 1955—56 was very snowy though the soil was not frozen deep in general. The winter turnip rape was greatly damaged by low-temperature parasitic fungi, i.e. the Typhula sp. fungi and the Sclerotinia sclerotiorum (Lib.) Bref. The Department of Plant Pathology arranged with Kasviöljy Oy. (an industrial concern which prepares oil from winter turnip rape) joint tests with PCNB products in different parts of the country in the winter turnip rape fields belonging to different farmers. The results of 15 tests (Table 1) were received. The damage was caused by low-temperature parasitic fungi and by abiotic factors (cold and water). Treatments of stads with 20 % PCNB in the autumn had noticeably increased the seed yields in many tests. In an observation plot test in Tikkurila in 1955—56 (Table 2) the losses during overwintering were caused by abiotic factors as well as low-temperature parasitic fungi. PCNB reatment in October was not effective against the fungi, but treatment carried out in November prevented the damages caused by the fungi and increased the yields. In the other tests (Table 3) treatment of winter turnip rape stands with PCNB, using 25 kg or 50 kg 20 % PCNB per hectare, effectively prevented damages from low-temperature pathogens resulting in considerable increases in the yields. In the test at the South Ostrobothnia Experiment Station the yield increasing effect proved uncertain. It should be noted that in one test at the Carelian Experiment Station a treatment carried out in the spring also improved the yield to some extent. In tests with winter turnip rape in 1955—56 the seed yields increased in most tests (in total 21 tests) with the use of a 20 % PCNB preparation, 25 or 50 kg per hectare. In three of the tests the increase in seed yields was over 100 % (1060—550 kg/ha), in five tests 100 % – over 50 % (1350—370 kg/ha), in eight tests 50 % – over 20 % (430—220 kg/ha) and in five tests below 20 % (230—0 kg/ha). Tests in 1956—57. In the autumn of 1956 scores of PCNB treatment tests with winter turnip rape were made in different parts of the country, mostly in S-W Finland. There were practically no injuries caused by low-temperature parasitic fungi in these cases the poor overwintering of the winter turnip rape being the result of injuries from cold and water. Tests in 1957— 58. In the winter there was a great deal of snow practically everywhere in Finland. In the late autumn the ground froze to a considerable depth which may explain why the injuries from low-temperature parasitic fungi in winter tirnip rape remained rather small. In southern Finland winter turnip rape overwintered very well. For reasons related above no special improvements in yields through the use of fungicides were achieved in the experiments of the winter 1957—58. One of the tests in Tikkurila did, however, give some indication of the effects of fungicides (Table 4). According to the test a treatment with BCNB in November, 100kg per hectare, distinctly resulted in an improvement in the yield while smaller quantities that were used remained ineffective. Treatment with PMA (phenylmercuryacetate) in October and November was similar in effect as the 20 % PCNB preparation administred in the quantity 100 kg per hectare. The amount of phenylmercuryacetate in the Verdasan preparation amounted to 425 g per hectare. The use of fungicides in the cultivation of winter turnip rape. If conditions for the development of low-temperature parasitic fungi are favourable, treatments of stads with fungicides in the autumn result in considerable increases in the yields by controlling the losses caused by the fungi. As winter turnip rape is frequently a failure in central, eastern and northern Finland owing to injuries from abiotic factors (2), treatment of stands of winter turnip rape in these parts of the country scarcely meets the case although it is possible in this way to control the losses from low-temperature pathogens. In southern and western parts of the country, where losses caused by water do not form a decisive obstacle to the cultivation of winter turnip rape, it may prove profitable to start using the fungicides in question in such places where injuries from low-temperature parasitic fungi have been observed.