Abstract
Benzimidazole-resistant field isolates of Botrytis cinerea, Cercospora beticola, Fusarium nivale and Mycosphaerella melonis showed an increased sensitivity to methyl N-(3, 5-dichloro-phenyl) carbamate (MDPC) on a nutrient medium as compared with the wild-type isolates. The difference in the sensitivity to MDPC between the resistant isolates and the wild-type ranged from about 8 times in F. nivale to about 80 times in C. beticola. In pot tests, MDPC was found to control gray mold and powdery mildew of cucumber, and Cercospora leaf spot of sugar beet caused by the resistant isolates, but not to be effective when the wild-type isolates were inoculated. Furthermore, MDPC showed systemic activity in plants and curative activity as well as preventive activity in controlling gray mold of cucumber. When mixed inoculation of the resistant isolate and the wild-type of C. beticola was made to the seedlings of sugar beet, mixed application of MDPC and benomyl was required to control the disease.
