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.