Azadirachtin-mediated reproductive response of the predatory pirate bug Blaptostethus pallescens

Abstract

The little-known pirate bug Blaptostethus pallescens Poppius is a biocontrol agent observed in tropical tomato fields in Brazil regulating fruit borer populations. In this study, the lethal response of B. pallescens to the bioinsecticide azadirachtin and to two synthetic insecticides, chlorpyrifos and deltamethrin, was assessed. The mild effect of the azadirachtin label rate (0.006 mg a.i. ml−1) on the predator (median lethal time (LT50) of 27 days), relative to label rates of deltamethrin (0.02 mg a.i. ml−1) and chlorpyrifos (1.44 mg a.i. ml−1) (with LT50 of 25 and 60 min, respectively) led to the assessment of its potential sublethal effects. Azadirachtin did not cause behavioral avoidance in the pirate bug, but the daily fecundity, adult progeny production and sex ratio were impaired when both male and female parents were exposed. These effects reduced the population growth of the predator in subsequent generations. Therefore, although safer than the conventional synthetic insecticides tested, the bioinsecticide azadirachtin does impair predator reproduction requiring attention when used in fields with this biological control agent.