Biological mode of action of Famoxadone on Plasmopara viticola and Phytophthora infestans

Abstract

Famoxadone (DPX-JE874, Famoxate ®) is a highly active, broad-spectrum fungicide from a new class of chemicals, the oxazolidinediones. Famoxadone inhibited sporangial differentiation and zoospore release and caused lysis of zoospores within minutes. Doses in the order of 0.01 mg l −1 were sufficient to lyse zoospores of both Plasmopara viticola and Phytophthora infestans. In the case of P. infestans, mycelial growth and direct germination of sporangia were also inhibited but higher doses were needed. In whole plant tests, famoxadone exhibited strong preventative control of both grape downy mildew and potato late blight with good residual activity of at least 7–10 days. No significant effect on disease control was observed when famoxadone was applied after inoculation. Both the in vitro and in vivo activities of famoxadone appeared complementary to that of cymoxanil which exhibited shorter residual activity but strong curative properties.