Activity of Fluazinam against Strains of Botrytis cinerea Resistant to Benzimidazoles and/or Dicarboximides and to a Benzimidazole‐phenylcarbamate Mixture

Abstract

Fluazinam is a new active ingredient for the control of grey mould, belonging to the novel broad spectum phenylpyridinamine fungicides. The effect of fluazinam was studied on one wild type and four strains of Botrytis cinerea, which had been isolated from vegetable crops in Greece, and were resistant to benzimidazoles and/or dicarboximides and to the mixture of benzimidazoles (carbendazim) + phenylcarbamates (diethofencarb). In vitro fluazinam was found to be highly active against strains of B. cinerea which were sensitive or resistant to benzimidazoles or exhibited multiple resistance to benzimidazoles, dicarboximides and to the mixture carbendazim + diethofencarb [EC50 and EC95 values (concentration of active ingredient that suppresses mycelial growth to 50 and 95%, respectively, of that of the fungus on fungicide‐free agar medium) calculated with probit analysis, ranged from 0.044 to 0.069 and 0.58 to 1.6 μg/ml, respectively]. No cross‐resistance was observed between fluazinam and the market products benomyl, iprodione or carbendazim + diethofencarb. Preventive applications of fluazinam in vivo completely inhibited infections of cucumber seedlings by all the above‐mentioned resistant strains of B. cinerea. Benomyl and iprodione did not effectively control the benzimidazole‐ and dicarboximide‐resistant strains. The mixture of carbendazim + diethofencarb insufficiently controlled the strain of B. cinerea with moderate resistance to benzimidazoles. The results of this investigation indicate that it should be possible to use fluazinam as an alternative in resistance management programmes against grey mould.