Susceptibility of Predaceous Hemipteran Species to Selected Insecticides on Soybean in Louisiana

Abstract

Toxicity of selected insecticides to hemipteran predators [i.e., Geocoris punctipes (Say), Nabis capsifonnis Germar, Nabis roseipennis Reuter, and Podisus maculiventris (Say)] was evaluated by contact with foliar residues and indirectly through the consumption of prey [i.e. soybean looper, Pseudoplusia include118 (Walker)] previously exposed to insecticides. Methyl parathion and permethrin generally were more toxic than newer insecticides after predators were exposed to treated foliage. Chlorfenapyr caused contact toxicity equal to permethrin and methyl parathion. Exposure to foliage treated with emamectin benzoate resulted in lower mortality as compared with chlorfenapyr. Foliage treated with Bacillus thuringiensis Berliner subsp. kurstaki had the lowest contact toxicity to hemipteran predators of all insecticides tested. Standard insecticides (i.e., methyl parathion and thiodicarb) caused low indirect toxicity to hemipteran predators after consumption of treated prey. Chlorfenapyr caused significantly greater indirect toxicity than emamectin benzoate, permethrin, and thiodicarb to adult N. roseipennis. Consumption of chlorfenapyr-treated prey also caused significantly greater mortality than imidacloprid, permethrin, spinosad, and thiodicarb to G. punctipes adults. These results demonstrate that most of the newer compounds were more selective than older insecticides. This greater selectivity will enable soybean producers to combat pests but conserve resident beneficial arthropod populations that help restrain pest resurgence and prevent secondary pest outbreaks.