Toxicity and Enzymatic Activity of Reduced Doses of Insecticides in Chrysoperla carnea1 and Bactericera cockerelli2

Abstract

The objective of this research was to compare the toxicity of reduced doses and enzymatic activity associated with insecticide tolerance to abamectin and profenofos on Chrysoperla carnea Stephens and its prey Bactericera cockerelli Sulc. Residual toxicity was measured at 0.1, 0.5, and 1.0\% of the recommended dose of abamectin and profenofos for controlling B. cockerelli. Measured were a-esterases, 8-esterases, glutathione S-transferases (GSTs), and oxidase content of larvae and nymphs of C. carnea and B. cockerelli exposed to the insecticides. The three abamectin concentrations killed more nymphs of the pest than did larvae of green lacewing. Profenofos at 1.0\% concentration was very toxic to the pest and its predator. At concentrations of 0.5 and 1.0, fewer died and was similar for both species. Abamectin killed fewer C. carnea than did profenofos at the three doses. Enzymatic activity of a and 8-esterase was greater for C. carnea compared with B. cockerelli exposed to abamectin and profenofos. Activity of the enzyme glutathione S-transferases (GSTs) and oxidase content where greater for B. cockerelli than C. carnea. The study demonstrated that abamectin was less toxic to C. carnea and more to B. cockerelli, suggesting the insecticide was very selective, which could be related to greater esterase enzymatic activity.