RESIDUAL TOXICITY OF DICOFOL, FORMETANATE HCl, PROPARGITE, HEXYTHIAZOX, AND CLOFENTEZINE TO EUROPEAN RED MITE ON PEACH

Abstract The persistence of toxic effects of the contact acaricides dicofol, propargite, and formetanate HCl and the ovicides clofentezine and hexythiazox to the European red mite, Panonychus ulmi (Koch), were tested by bioassays of disks cut from treated peach foliage. Effects of dicofol were more persistent than propargite or formetanate HCl to susceptible mites. Mortality on dicofol-treated foliage was >50% for more than 15 days. Propargite killed >50% of females for 10 days after application, whereas the toxicity of formetanate HCl deposits declined rapidly after 7 days. Mortality of dicofol-resistant mites was less than for susceptible mites. However, resistant mites were affected (>50% killed) by dicofol residues up to 7 days old. The toxic effects of the ovicides clofentezine and hexythiazox persisted for at least 30 days and at the rates tested were approximately equally toxic. Formetanate HCl and propargite residues were less persistent (half-life 8–9 days) than the other compounds. Dicofol residues had a half-life of about 15 days but approximately 10% of residues persisted for 65 days. Residues of clofentezine and hexythiazox declined more gradually (half-life = 15–20 days) than other compounds and persisted at approximately 10% of initial residues after 65 days.