Lethal and Sublethal Effects of Three Novel Insecticides on Biological Parameters of Pink Bollworm, Pectinophora gossypiella (Lepidoptera: Gelechiidae).

Pink bollworm (Pectinophora gossypiella) is a serious pest of cotton that causes huge economic losses in major cotton-growing regions. The development of resistance to transgenic Cry1Ac and Cry2Ab in India has led to long-term reliance on insecticides, thus enables the larvae to experience sublethal effects due to its concealed feeding behavior. This study investigated the impact of sublethal concentrations (LC10 and LC30) of emamectin benzoate, spinetoram, and spinosad on P. gossypiella. The results showed that emamectin benzoate was more toxic to P. gossypiella (LC50-2.12 mgL-1) than spinetoram (LC50-3.52 mgL-1) and spinosad (LC50-7.44 mgL-1). The developmental time and adult preoviposition period (APOP) were extended, while fecundity, egg hatchability, and ovipositional days were reduced at sublethal concentrations in treated populations than the control group. Among treated insecticides, mean fecundity of P. gossypiella was significantly reduced in emamectin benzoate LC10 (91.03 ± 3.87/female) and LC30 (62.89 ± 3.22/female) treated population than spinetoram and spinosad. Further, the biological parameters including the intrinsic rate of increase (r), finite rate of increase (λ), and net reproductive rate (R0) were also significantly decreased in the treated population as compared with untreated insects. Our results indicated that emamectin benzoate was effective against P. gossypiella and highlighted the importance of sublethal effects of insecticides on target insects to ensure the comprehensive evaluation and rational use of insecticides under field conditions.