Rhizoctonia solani damping-off on spring turnip rape and spring rape (Brassica spp.) in Finland

Abstract

Damping-off occurred in 90 % of the spring oilseed rape fields surveyed in 1981—1982. On the average, 10 % of the plants were infected with damping-off.6 % of the fields were severely infected (> 30 % of the plants affected) by damping-off and 38 % were uninfected or only slightly infected ( ≤ 5% of the plants affected). The incidence of damping-off was higher in those fields which had been under oilseed rape in earlier years. Ina crop rotation experiment, the amount of damping-off increased from 2 % to 20 %, and finally to 38 %, depending upon whether turnip rape had been grown on the same part of the field once, twice or three times. Crops other than Cruciferous ones were grown for 1 or 3 years between the turnip rape crops. Rhizoctonia solani Kühn was isolated from 76 % of the affected plants. The R. solani isolates produced severe damping-off on rape and turnip rape in pathogenicity tests. R. solani isolates from barley, potato and lettuce brought about only mild cases of damping-off, or else only a decrease in the growth of the plants. Fusarium avenaceum Sacc. was the only other isolated fungus which was pathogenic.