Comparative Toxicity of Fenpyroximate to the Predatory Mite, Amblyseius womersleyi SCHICHA and the Kanzawa Spider Mite, Tetranychus kanzawai KISHIDA (Acarina: Phytoseiidae, Tetranychidae)

Abstract

The relative toxicity of fenpyroximate to the predatory mite, Amblyseius womersleyi SCHICHA and the kanzawa spider mite, Tetranychus kanzawai KISHIDA was evaluated in laboratory studies. Adult females and eggs of both species were placed on bean leaf discs dipped in several concentrations of fenpyroximate. Fenpyroximate was much less toxic to A. womersleyi than to T. kanzawai, Although the survival rate of adult females of A. womersleyi tended to decrease with increasing concentrations of fenpyroximate, 58-74% of the predators survived at concentrations of 6.25-50 ppm. However, reproduction was not significantly reduced at any of the concentrations tested. At 6.25-50 ppm, fenpyroximate did not affect the hatch ability of A. womersleyi eggs or the development time of immature predators. Survival of immature predators significantly decreased with increasing fenpyroximate concentration, however, 16-48% of immature predators reached adulthood at 6.25-50 ppm. Adult female predators survived on a diet of spider mites intoxicated with fenpyroximate, and their fecundity and the sex ratio of the progeny were not significantly affected. Fenpyroximate at selective sublethal concentrations (i, e., 6.25-12.5 ppm) could be of value in adjusting the prey/predator ratio in integrated management of T. kanzawai.