The Joint Toxicity of Different Temperature Coefficient Insecticides on Apolygus lucorum (Hemiptera: Miridae)

Abstract

The effect of temperature on the cotoxicity coefficient (CTC) value was used to evaluate mixture efficacy of different temperature coefficient chemicals from 15 to 35°C by exposing third-instar Apolygus lucorum (Meyer-Dür) to dip-treated asparagus bean pods. The results indicated the joint toxicity of same temperature coefficient insecticide (TCI) types were unaffected by temperature. This means that even when temperatures change, the mixture ratios of the highest CTC values remained the same, and the effect of temperature on the joint toxicity of same TCI types was only on the CTC values. However, the effect of temperature was variable when considering the joint toxicity of different TCI types. The effect of temperature on the joint toxicity of both strong positive and strong negative TCI types was clear, and the highest CTC values of mixture ratios changed with temperature regularly. When comparing the influence of temperature between strong/slight positive/negative insecticides, the results indicated a greater influence of the strong TCI. Paradoxically, the highest CTC value of the imidacloprid and methomyl mixture did not change with temperature changes consistently, even with the variance of imidacloprid ratios, a strong TCI. These results will guide pest managers in choosing the most effective insecticide mixtures for A. lucorum control under given environmental conditions.

Keywords: Apolygus lucorum; insecticide; joint toxicity; temperature effect.