Fate of Propaphos (Kayaphos®) Applied on Seedling Box

The fate of [O, O-di-n-propyl O-4-methylthiophenyl phosphate (Propaphos, Kayaphos®, Nippon Kayaku Co., Ltd.)] applied on seedling box was studied in rice plant and paddy soil after transplanting onto paddy field. In paddy soil, only propaphos was detected but in rice plant propaphos was rapidly oxidized to its sulfoxide and sulfone. Especially, in rice leaves propaphos was detected slightly although its oxidative metabolites were detected in large amount. Since insecticidal activities of propaphos and its oxidative metabolites are nearly equal, it was considered that the efficacy of propaphos applied on seedling box for control of green rice leaf hopper (Nephotettix cinciticeps) and rice leaf beetle (Lema oryzae) was attributed to not only Propaphos but also its oxidative metabolites in rice plant. Propaphos and its oxidative metabolites were not detected in harvested rice grains when 100g of 5% propaphos granules per box was applied just before transplanting.