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

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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.