Negative cross-resistance to N-phenylanilines in benzimidazole- resistant strains of Botrytis cinerea, Venturia nashicola and Venturia inaequalis

A new series of compounds with high contra-selective activity against benomyl-resistant fungal strains was found among ring-substituted N-phenyl-anilines. Hydrophobic substitution in one of the benzene rings, together with the secondary amine character of the molecule, are important factors for high fungitoxicity. The sensitivities of benomyl-resistant isolates to some representatives of the N-phenylanilines equal or even surpass their sensitivity to diethofencarb or MDPC. The negative cross-resistance with benzimdazole fungicides is valid for strains of Botrytis cinerea, Venturia nashicola and Venturia inaequalis. The strains of B. cinerea with double insensitivity to benzimidazoles and phenyl-carbamates are insensitive also to N-phenylanilines. However, the similarly double-insensitive strain of V. nashicola was found to be just as sensitive to the N-phenylanilines tested as the strain resistant only to benzimidazoles. The latter result revealed an important bonus compared with diethofencarb. Preventive application of one of the most active representatives of the N-phenylanilines to young cucumber plants was effective against infection with benomyl-resistant isolates of B. cinerea. Moderate apical translocation after root-dipping was also observed.