Residual Effects of Insecticides on Deraeocoris brevis (Hemiptera: Miridae)

Abstract

Deraeocoris brevis (Uhler) is a key predatory natural enemy of insects and mites in pear orchards in the United States. Insecticides used for crop protection in pear orchards and their residues can negatively affect populations of D. brevis. The focus of this study was to investigate the field-aged residual effects of lambda-cyhalothrin, spinetoram, and chlorantraniliprole insecticides on D. brevis through contact exposure. An airblast sprayer was used to apply the high label rate of insecticides on pear trees. Leaves were collected from the experimental trees at 1 d after treatment (DAT) and then at 7-d intervals up to 21 DAT. Adults and nymphs were exposed to leaves with insecticide residues or untreated control for 72 h in the laboratory. The nymphs that survived the treatments were reared until they emerged as adults. The surviving paired adults were reared until death. The treated nymphs were assessed for acute mortality, survival, developmental time, and the sex ratio if they emerged as adults. The treated adults were assessed for acute and chronic mortality, fecundity, fertility, and longevity. Both nymphs and adults exposed to leaf residues of lambda-cyhalothrin had significantly higher acute mortality compared with the insects exposed to the control. When compared with the control treatment, the toxicity of field-aged residues of lambda-cyhalothrin, chlorantraniliprole, and spinetoram can persist over a longer period of time. Similar patterns were observed in previous laboratory and field experiments on D. brevis. We discuss the residual effects of three insecticides through contact exposure of D. brevis.