Impacts of azadirachtin and chlorantraniliprole on the developmental stages of pirate bug predators (Hemiptera: Anthocoridae) of the tomato pinworm Tuta absoluta (Lepidoptera: Gelechiidae)

Abstract

Conservation of natural enemies is an important approach for enhancing biological control. Selective insecticides have become important for managing arthropod pests, and the prospects for their use in combination with biological control agents are increasing. In addition, progress has been made in recent decades to develop reduced-risk insecticides that have novel modes of action and, therefore, likely to have a minimum non-target effect. In this study, we use a series of laboratory bioassays to investigate the impact of two reduced-risk insecticides, azadirachtin and chlorantraniliprole, on the egg, nymph and adult stages of two predatory pirate bugs, Amphiareus constrictus (Stal) and Blaptostethus pallescens Poppius (Hemiptera: Anthocoridae), important predators of the tomato pinworm Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae). All three stages were exposed to the label recommended field rate of these two insecticides, which is indicated for the control of T. absoluta. Neither azadirachtin nor chlorantraniliprole affected the mortality of adult predators or their egg hatchability, suggesting a safe acute toxicity for these stages. However, azadirachtin and chlorantraniliprole negatively decreased the capacity of predator nymphs to reach the adult stage. This decrease can directly affect the size of the predator population in the next generation, and may undermine the biological control of pests such as T. absoluta. In general, our results call for caution when using these reduced-risk insecticides in integrated programs of chemical and biological control of this pest.