Biological impact, oxidative stress and adipokinetic hormone activities of Agrotis ipsilon in response to bioinsecticides

The use of biological control products enhances the reduction of harmful pressures on the environment caused by the use of conventional pesticides. Therefore, this study aims to evaluate the toxicity of eight bioinsecticides on the black cutworm Agrotis ipsilon (Hufnagel) (Lepidoptera: Noctuidae) to understand the relationships between insecticide exposure and insect response at the individual and population levels. The bioassay results showed that emamectin benzoate had high toxicity against A. ipsilon second instar larvae with an LC50 of 0.007 (mg/L). Sublethal concentration (LC30) of emamectin benzoate, spinosyn group and Bacillus thuringiensis formulation (Dipel 2X) had significantly prolonged pupal period. In addition, emamectin benzoate significantly decreased the number of eggs laid per female (135.3 ± 6.919) compared with the control treatment. Thus, the formulation of chlorfenapyr showed a 1.26-fold reduction in hatching rate. Meanwhile, the activities of oxidative stress enzymes (catalase, superoxide dismutase, lipid peroxidase, and glutathione reductase) were significantly affected due to exposure to sublethal concentration. Changes in adipokinetic hormone (AKH) transcriptional regulation were detected via SQ-PCR via using cDNA synthesized from mRNA isolated from treated A. ipsilon larvae. The results showed a higher transcription rate of AKH in spinotram-treated larvae with a 1.42-fold increase over untreated larvae. Our results provide useful information for integrated pest management programs for A. ipsilon by using bioinsecticides.