Toxicity of thiamethoxam to Tetranychus urticae Koch and Phytoseiulus persimilis Athias-Henriot (Acari Tetranychidae, Phytoseiidae) through different routes of exposure.

This study evaluates the effect of thiamethoxam on Tetranychus urticae and its predator Phytoseiulus persimilis by considering different routes of exposure (topical, residual and contaminated food exposures) and their combinations. Thiamethoxam effects on T. urticae were higher when residual and contaminated food exposures were considered. On P. persimilis, the total effect was higher in residual and contaminated prey exposures compared with topical exposure, and all combinations of routes of exposure attained a total effect higher than 90%. Lethal and sublethal effects occurred in residual and contaminated food exposures, while only sublethal effects occurred in topical exposure of predators and prey. By limiting exposure to thiamethoxam to ingestion of contaminated food only, the impact of the pesticide was more favourable to P. persimilis than to its prey.