Sublethal and hormesis effects of beta-cypermethrin on the biology, life table parameters and reproductive potential of soybean aphid Aphis glycines

Beta-cypermethrin has long been recommended as an effective pesticide to control the soybean aphid, Aphis glycines Matsumura, a serious pest in soybean crops. Besides acute toxicity, it leads to changes in life history traits of A. glycines , notably its reproductive potential. This study has assessed the effects of five sublethal concentrations (0.625, 1.25, 2.5, 5 and 10 µg/L) of beta-cypermethrin on different life history traits of A. glycines . Exposure to these concentrations caused shorter oviposition period and reduced adult longevity. The strongest stimulatory effect on aphid reproduction was achieved when exposed to a higher sublethal beta-cypermethrin concentration (5 µg/L). Net reproduction rate ( R 0 ), intrinsic rate of increase ( r m ) and finite rate of increase (λ) were significantly higher than that of the control, increasing by 20.58, 4.89 and 2.06%, respectively. We found no significant difference in mean generation time (T) between the treatment of 5 µg/L beta-cypermethrin and the control. However, when the concentration increased to 10 µg/L, the reproduction behavior was restrained and the mean generation time (T) was shortened, resulting in significant decrease in R 0 and T by 16.58 and 3.83%, respectively. In conclusion, a sublethal concentration (5 µg/L) of beta-cypermethrin triggered the strongest hormesis on A.glycines , thus providing valuable knowledge on the sublethal effects of this insecticide on soybean aphids. Hormesis may be one of the mechanisms underlying pest resurgences, and better knowledge would enable a more effective use of insecticides in Integrated Pest Management programs.