Relative Toxicity of Abamectin to the Predatory Mite Phytoseiulus persimilis (Acari: Phytoseiidae) and Twospotted Spider Mite (Acari: Tetranychidae)

Abstract

The relative toxicity of abamectin to the predator Phytoseiulus persimilis Anthias-Henriot and the spider mite Tetranychus urticae Koch was assessed in laboratory studies. Eggs and female adults of both species were placed on bean ( Phaseolus vulgaris L.) leaf disks dipped in several concentrations of abamectin. Abamectin was much less toxic to the predator than to the spider mite. At concentrations of 0.08-16 ppm, abamectin did not significantly affect the survival and mobility of P. persimilis , but reproduction was significantly reduced at high concentrations (8 and 16 ppm). Adult female predators survived on a diet of spider mites intoxicated with abamectin, although their reproductive rate was decreased by 27 to 53%. At 1-16 ppm, abamectin did not affect the hatch of P. persimilis eggs or the developmental time of resulting immature predators. Survival of immature predators was not significantly affected at 1-4 ppm, but was reduced to an average of 54.3% at 8 and 16 ppm. The mobility of immature P. persimilis was slightly affected only at 16 ppm. Abamectin at selective sublethal concentrations (i.e., 1-4 ppm) could be of value in adjusting predator /prey ratios in integrated management of spider mites.