Effect of Insecticides on Two Predators of the Colorado Potato Beetle (Coleoptera: Chrysomelidae)

Abstract

The effect of insecticides currently used in commercial eggplant fields to control the Colorado potato beetle, Leptinotarsa decemlineata (Say) on two egg predators, Coleomegilla maculata DeGeer and Chysoperla carnea (Stephens) was evaluated. Mortality from contact exposure to leaf residues, topical applications, and ingestion of contaminated eggmasses was compared for the following insecticides: esfenvalerate alone and in combination with piperonyl butoxide (PBO); oxamyl; PBO; and rotenone alone and in combination with PBO. Topical exposure and feeding studies were conducted using concentrations 1.00, 0.90, 0.80, 0.70, 0.60, 0.50, 0.40, 0.30, 0.20, and 0.10X the maximum labeled dose; leaf exposure studies were conducted using concentrations 1.00, 0.75, 0.50, and 0.25X the maximum labeled dose. Mortality of C. maculata adults and larvae from topical exposure was high after 48 h of exposure for all chemicals and doses. Mortality from topical exposure was low for C. carnea larvae in all cases when compared to PBO alone. Mortality from exposure to leaf residues was low in all cases for C. maculata adults but varied, depending on dose and chemical, for both C. maculata and C. carnea larvae. For all treatments, ingestion of treated eggs negatively affected the feeding and survival of C. maculata adults and larvae and C. carnea larvae. Esfenvalerate combined with PBO had the greatest effect on C. maculata adults; rotenone combined with PBO had the greatest effect on C. maculata larvae; esfenvalerate combined with PBO affected C. carnea larvae the most.