Toxicity of Selected Insecticides and Insecticide Mixtures in a Glass-Vial Bioassay of Southern Green Stink Bug (Hemiptera: Pentatomidae) from Central Texas

Abstract

The southern green stink bug, Nezara viridula (L.) (Heteroptera: Pentatomidae), is cosmopolitan in distribution and feeds on a multitude of food and fiber crops. It induces abscission of bolls of cotton, Gossypium hirsutum L., and reduces seed cotton yield, gin-turnout, and fiber quality. Also, the bug vectors bacterial and fungal pathogens causing necrosis of the locule and rotting the bolls. Control options are mostly dependent upon and limited to the use of insecticides. Data are needed to assess the toxicity of currently available insecticides and develop baseline mortality data to monitor resistance of the insect to insecticides in Central Texas. We studied the toxicity of selected organophosphate and pyrethroid insecticides in a glass-vial bioassay to adult southern green stink bugs captured in blacklight traps. Dicrotophos was six times more toxic than acephate to southern green stink bug. Toxicity of acephate and chlorpyrifos was comparable. The order of toxicity of pyrethroids to southern green stink bug was γ-cyhalothrin > zeta-cypermethrin > λ-cyhalothrin > Cypermethrin > bifenthrin. Mixtures of technicalgrade active ingredients were 4- to 7.5-fold more toxic to southern green stink bug compared to commercially-formulated insecticides. The lesser efficacy of the commercial formulations suggests the active ingredients used in the mixtures failed to potentiate, probably because of lack of additivity or synergism in the composition of active ingredients in the formulations. The inert and other ingredients in the formulations may have played a part as well.