Sublethal effects of emamectin benzoate on development, reproduction, and vitellogenin and vitellogenin receptor gene expression inThrips hawaiiensis(Thysanoptera: Thripidae)

Abstract Thrips hawaiiensis (Morgan) (Thysanoptera: Thripidae) is a sap-sucking pest that seriously damages several crops and reduces their economic value. Exposure to low concentrations of insecticides may have a sublethal effect on surviving insects. In order to provide a reference for the rational application of emamectin benzoate, its sublethal effects on the development and reproduction of T. hawaiiensis were evaluated. Pupal development time was significantly shorter in T. hawaiiensis treated with sublethal concentrations of emamectin benzoate (LC10 and LC20) than in control. Female adult longevity and female total longevity were significantly longer following LC20 treatment than in the control and LC10 treatment groups. Nevertheless, male adult longevity and male total longevity were significantly shorter in the LC10 treatment group than in the control and LC20 treatment groups. The sublethal concentration of emamectin benzoate (LC20) significantly shortened the preadult stages and the mean generation. Meanwhile, it significantly increased the finite rate of increase, intrinsic rate of increase, and net reproductive rate. The fecundity was significantly higher after LC20 treatment than after LC10 and control treatments. Compared with the control group, the LC10 and LC20 groups of T. hawaiiensis adults showed a significantly higher expression of the vitellogenin (Vg) and vitellogenin receptor (VgR) genes, which played a key role in increasing their fecundity. These findings suggest that short-term exposure to sublethal concentrations of emamectin benzoate may lead to a resurgence and secondary outbreak of T. hawaiiensis infestation. The results have practical applications for the management of this important and noxious pest.