Abstract
One hundred and twenty isolates of Pseudocercosporella herpotrichoides, causal fungus of eyespot of wheat, were tested for sensitivity to benzimidazoles (thiophanatemethy 1 and benomyl). They were divided into three types; sensitive, moderately resistant and highly resistant, of which minimum inhibitary concentration (MIC) to benomyl is 2mg, 20mg and > 200mg/l, respectively. Surveys of 2 78 winter wheat fields randomly selected in Hokkaido in 19 8 9, showed that benzimidazoleresistant strains were common and widespread. Resistant strains were obtained from 65.5% of fields and the proportion of resistant isolates was 5 0.0%. In the eastern region, where benzimidazole fungicides have been applied to control sclerotinia snow mold, most of all strains were resistant to benzimidazole. Experiments in three fields, where the frequency of resistant isolates was different, suggested that benzimidazole fungicides were able to control eyespot in such fields as frequency of resistant isolates were below 30%.
