Development of a novel fungicide, pyribencarb

Pyribencarb is a novel benzylcarbamate-type fungicide against a wide range of plant pathogenic fungi, especially gray mold caused by Botrytis cinerea and stem rot caused by Sclerotinia sclerotirum. The target site of pyribencarb is cytochrome b of complex III in the electron transport system of the respiratory chain. On the other hand, the inhibitory potency of pyribencarb to the succinate-cytochrome c reductase activities of plants, rats and carp was relatively weak compared with those of strobilurin fungicides, indicating that pyribencarb is a novel Qo inhibitor of cytochrome b, whose properties are superior to the well-known Qo inhibitor fungicides in terms of selectivity and selective toxicity in the target. The inhibitory effects of pyribencarb to the cytochrome b enzyme on the transfer system of a QoI-resistant strain of B. cinerea are stronger than those of other QoI fungicides. Pyribencarb exhibited adequate control in the field experiments where QoI-resistant strains existed. This indicated that, although QoI-resistant strains develop cross-resistance against pyribencarb, as well, the extent of sensitivity reduction in QoI-resistant strains to pyribencarb was clearly lower than to other QoI fungicides. Among the QoI fungicides, pyribencarb is assumed to have unique properties. Pyribencarb belongs to the benzylcarbamate-analogue class, not the strobilurin-analogue class. Therefore, pyribencarb is thought to be a new type of QoI fungicide (BC-QoI).