Toxic effects of seven pesticides to aphid parasitoid, Aphidius gifuensis (Hymenoptera: Braconidae) after contact exposure

Abstract

The toxic effects of pesticides have been widely reported on aphid parasitoids, but few studies have been devoted to assessing the toxicity of chemicals to parasitoid, Aphidius gifuensis. In this study, A. gifuensis was exposed to seven commonly used pesticides at their highest recommended field concentrations and the toxic effects were evaluated. All the seven pesticides decreased the parasitism rates after the adults were exposed, especially thiamethoxam and dinotefuran by 35.3 and 32.3%, respectively. In addition, thiamethoxam, dinotefuran, emamectin benzoate and profenofos shortened the longevity of next generation with 59.3h, 64.7h, 66.8h and 61.9h, respectively. However, pymetrozine and azoxystrobin had a low toxicity to the wasps. In the persistent toxicity test, at 1–14 DAT (day after treatment), thiamethoxam, bifenthrin and dinotefuran greatly affected the survival and parasitism of adults; followed by profenofos and emamectin benzoate. After the mummies were exposed to the pesticides, the egg and larval stages were more susceptible than the pupal stage of A. gifuensis. The sex ratio of newly emerged A. gifuensis was not affected. The findings of the present study provide informative data for the implementation of biological and chemical control strategies in the integrated pest management of aphids. In addition, our findings contribute to the determination of an effective time interval for the release of parasitoids when a specific pesticide is applied in the field.