Multiple Routes of Pesticide Exposure and the Risk of Pesticides to Biological Controls: A Study of Neem and the Sevenspotted Lady Beetle (Coleoptera: Coccinellidae)

Abstract

Microcosms were used to illuminate community-level interactions among the pea aphid, Acyrthosiphon pisum Harris (Homoptera: Aphididae), and the sevenspotted lady beetle, Coccinella septempunctata L., after a spray exposure to a commercial neem pesticide. The instantaneous rate of increase (r1) of pea aphid populations was used as a response variable in a 2 × 3 factorial experiment. Microcosms were treated with 100 ppm (mg/liter) or 600 ppm azadirachtin, the active ingredient in the commercial neem insecticide, or with water in the presence or absence of adult or 4th instar lady beetles. We compared our results with those of a previous study where C. septempunctata was exposed to only 1 route of exposure, direct application. Results from the previous study indicated that 100 ppm of the neem insecticide was sublethal ( 0.05) interaction between the predator and the pesticide was detected indicating that the chemical and biological control agents are not working synergistically. Furthermore, exposure to the pesticide in micrososms significantly reduced or completely eliminated oviposition in adult C. septempunctata, and all of the larval lady beetles exposed to 100 or 600 ppm died within 10 d of treatment. Based on these results, we question the value of toxicity tests where only 1 route of pesticide exposure is considered.