Development of a New Fungicide, Diethofencarb

Diethofencarb [isopropyl N-(3, 4-diethoxyphenyl)carbamate] is a new carbamate fungicide developed by Sumitomo Chemical Co., Ltd. This compound has an outstanding activity against benzimidazole-resistant gray mold of fruit trees, grapes, and vegetables caused by Botrytis cinerea. One of the most effective ways to cope with resistance of plant pathogens is considered to be the use of fungicides to which resistant strains show negatively correlated cross-resistance. Through extensive investigations to search for N-phenylcarbamates with a potent fungicidal activity against benzimidazole-resistant fungi, we synthesized an isopropyl N-phenylcarbamate having 3, 4-diethoxy substituents on the benzene ring, named diethofencarb, to which the resistant strains of B. cinerea exhibited negatively correlated cross-resistance. Diethofencarb controled benzimidazole-resistant strains of B. cinerea curatively as well as preventively and showed systemic activity in plants. This fungicide did not inhibit germination of conidia of the benzimidazole-resistant B. cinerea, but the germ tubes were distored and swollen. Their abnormal morphology was quite similar to that of the wild type isolates treated with a benzimidazole fungicide, carbendazim. In field trials, the combination of diethofencarb with carbendazim (Sumico®), another benzimidazole fungicide, thiophanatemethyl (Gtter®), or a dicarboximide fungicide, procymidone (Sumiblend®) showed excellent performance for control of gray mold diseases where benzimidazole-resistant strains and the wild type ones coexisted.