EFFICACY OF PHOSMET AND AZINPHOSMETHYL FOR CONTROL OF MAJOR INSECT PESTS OF APPLE IN ONTARIO

Phosmet (Imidan 50% WP) applied at 1.22 kg a.i./ha controlled the codling moth, Cydia pomonella (L.), apple maggot, Rhagoletis pomonella Walsh, and plum curculio, Conotrachelus nenuphar Herbst, in Ontario apple orchards for more than 3 weeks. Although rain removed phosmet deposits and climatic conditions varied widely during 1971–76, results consistently showed that good pest control was obtained. Satisfactory results were also obtained with azinphosmethyl (Guthion 50% WP) applied at 0.45 kg a.i./ha. Toxicological studies showed that phosmet deposits on the lower surface of apple leaves produced 38–100% mortality of first instar codling moth larvae 15 days after application depending on the time the pesticide was applied. Fifty per cent and 95% lethal residues were 0.18–0.68 μg/cm 2 and 0.50–1.36 μg/cm 2 of leaf surface, respectively. The toxicity of the residues declined considerably 22 days after application. A phosmet deposit of 0.5 μg/cm 2 15–22 days after spray application is suggested as the minimum level required to obtain an economically acceptable level of control in the field.