Effects of Insecticides on Invertebrate Predators and Their Cereal Aphid (Hemiptera: Aphididae) Prey: Laboratory Experiments

Abstract

The effects of three insecticides on a guild of natural enemies and their prey were determined in the laboratory. The cereal aphid Meropolophium dirhodium Walker (Hemiptera: Aphididae) and six potentially important predators were exposed to dry insecticide films for 24 h. after which time they were examined and recorded as alive, moribund, or dead. The insecticides tested were pirimicarb, cypermethrin, and methyl parathion. The predators tested were the insects Coccinella septempunctata L. (Coleoptera: Coccinellidae), Syrphus spp. (Diptera: Syrphidae), Pterostichus melanarius Illiger (Coleoptera: Carabidae). Nebria brevicollis F. (Coleoptera: Carabidae). Agonum dorsale Pont. (Coleoptera: Carabidae), and spiders, Erigone spp. (Araneae: Linyphiidae). Methyl parathion was overall the most toxic compound. cypermethrin was less toxic, and pirimicarb was the least toxic. The relative susceptibility of the predators and the aphid varied considerably between insecticides, as did the slope of the dose-response curve. We discuss our data in the light of these findings, particularly the possibility that different insecticides might be used to differentially kill selected groups of predators, their prey in the field, or both.