Lethal and behavioral effects of selected novel pesticides on adults of Trichogramma pretiosum (Hymenoptera: Trichogrammatidae).

BACKGROUND

Growing demand for reduced chemical inputs in agricultural systems requires more effective integration of biological control with pesticides. The egg parasitoid Trichogramma pretiosum Riley is an important natural enemy of lepidopteran pests, used in biological control. In an investigation of the interaction of T. pretiosum and pesticides, we studied the acute toxicity of 19 pesticides (insecticides, miticides, fungicides and herbicides) to adult parasitoids and the behavioral effects of 11 pesticides on foraging parasitoid females, including host antennation, stinging and host feeding.

RESULTS

At recommended field doses, fipronil, dinotefuran, spinetoram, tolfenpyrad and abamectin induced nearly 100% adult mortality within 24 h of exposure to treated cotton leaves by comparison with controls. Acetamiprid was also toxic, but significantly less so than the former materials. The other pesticides had no significant toxic effects. Only glufosinate ammonium exhibited increased toxicity among the non-toxic materials when increased two- or fourfold over recommended rates. The foraging behavior of parasitoids was affected only by tolfenpyrad among the materials tested.

CONCLUSION

Most novel pesticides, except for several insecticides, exhibited little to no acute toxicity to the parasitoid. Parasitoid foraging behavior was only affected by tolfenpyrad, indicating that parasitoids could successfully forage on eggs treated with most pesticides evaluated. Therefore, many of these pesticides may have good compatibility with Trichogramma.