Multiple fungicide resistance to benzimidazoles, dicarboximides and diethofencarb in field isolates of Botrytis cinerea in Israel

During the period January‐March 1989, 15 greenhouses at 12 sites in Israel were surveyed for the presence of fungicide‐resistant strains of Botrytis cinerea , using a fungicide‐amended Botrytis ‐selective medium. Resistance to benzimidazoles (Ben R ) and to dicarboximides (Dic R ) was frequent in most sites. Resistance to carbendazim + diethofencarb (Ben R NPC R ) was found in all eight sites in which a mixture of these fungicides had been used against grey mould, but not in other sites. A new phenotype of multiple fungicide resistance was found among these isolates. The new phenotype, designated Ben R Dic R NPC R , combines the three previously described characteristics of resistance to benzimidazole, dicarboximide and N ‐phenylcarbamate fungicides. It was found only in cucumber greenhouses that had been sprayed with the fungicide mixture carbendazim + diethofencarb against grey mould. Isolates of this phenotype were pathogenic in artificial inoculation of cucumber cotyledons treated with carbendazim, iprodione or carbendazim + diethofencarb.