Sensitivity to diethofencarb mixtures was monitored in 623 isolates of Botrytis cinerea collected from thirty four tomato fields in Tokyo from 1994 to 1996. Through the monitoring, resistant strains to diethofencarb mixtures were found for the first time in Tokyo. In 1996, the frequency of the resistant strain increased to 53.2% of all isolates and the phenotype which is highly resistant to benzimidazole and weakly resistant to diethofencarb (HR·WR) was the most dominant, 71.8% in all resistant strains.
