Indirect Effects of Imidacloprid on Natural Enemies of Spider Mites in Two Systems

Abstract

With a growing number of reports showing secondary outbreaks of spider mites following systemic applications of imidacloprid, a study was designed to test the indirect effects of this insecticide on natural enemies of spider mites. We exposed two predators, Chrysoperla rufilabris and Stethorus punctillum, to mites that were reared on boxwoods and elms treated with imidacloprid and examined prey consumption, predator mobility and mortality. Mites reared on treated foliage were extremely toxic to predators, eliciting sharp reductions in feeding, locomotion, and longevity. These findings document that non-target pests feeding on plants treated with imidacloprid cause lethal and sublethal responses in natural enemies. We discuss implications on the compatibility of imidacloprid with IPM practices and infer impacts on generalist and specialist natural enemies.