Effects of sublethal concentrations of emamectin benzoate and chlorantraniliprole on digestive enzyme activity, growth and reproduction, of Spodoptera frugiperda
Author of the article:LU Zhi-Hui, LI Hao, TAO Xuan, WAN Kun, CHEN Yao, MA Rui-Xin, GUI Fu-Rong, CHEN Ya-Ping
Author's Workplace：State Key Laboratory of Conservation and Utilization of Biological Resources of Yunnan, College of Plant Protection, Yunnan Agricultural University, Kunming 650201, China
Key Words：sublethal concentration; digestive enzymes; developmental period; body weight; fecundity
Abstract：
[Objectives] The objective To investigate the effects of two different insecticides on the digestive enzymes of Spodoptera frugiperda larvae, and assess changes in the biological characteristics of the offspring of S. frugiperda exposed to sublethal concentrations (LC25) of these pesticides. [Methods] Third instar S. frugiperda larvae were exposed to sublethal concentrations of emamectin benzoate and chlorantraniliprole, based on the virulence of each pesticide. These larvae were then fed on wheat leaves and the pepsin (Pepsin), α-amylase (α-AMS), and lipase (LPS) activity levels of both the F0 (parental) and F1 (offspring) generations were measured and compared 48 hours after feeding. In addition, we analyzed the impact of exposure to sublethal pesticide concentrations on offspring developmental period, weight, oviposition characteristics, and population parameters. [Results] Exposure to sublethal concentrations of both insecticides significantly reduced the pepsin activity of the F0 generation compared to the control (P<0.05). Furthermore, exposure to emamectin benzoate consistently, and significantly, inhibited the pepsin activity of F1 larvae. Exposure to chlorantraniliprole did not, however, significantly reduce pepsin activity. No significant differences were observed in α-amylase and lipase activity compared to the control group. Exposure to sublethal pesticide concentrations reduced the weight of F1 6th instar larvae and pupae, significantly prolonged the pupal period, decreased the oviposition period, and reduced average egg production per female. These effects resulted in a significant decrease in the F1 generation’s net value-added rate (R0), intrinsic growth rate (rm), weekly growth rate (λ), and also extended its average generation period (T) and population doubling time (DT). [Conclusion] Exposure to sublethal concentrations of emamectin benzoate and chlorantraniliprole, inhibited the pepsin activity of S. frugiperda larvae, and prolonged the developmental period, lowered the fecundity and slowed the population growth of the F1 generation. Exposure to sublethal concentrations of these two insecticides can therefore provide sustained control of S. frugiperda.