Evaluating the sublethal impacts of deltamethrin, cypermethrin, and chlorantraniliprole on the population growth and demographic traits of <i>Rhopalosiphum padi</i> (L.) (Hemiptera: Aphididae)

This study evaluated the sublethal and demographic effects of deltamethrin, cypermethrin, and chlorantraniliprole on the bird cherry-oat aphid, <i>Rhopalosiphum padi</i> (L.) (Hemiptera: Aphididae). The age-stage, two-sex life table model was used to assess population parameters following exposure to LC₃₀, LC₄₀, and LC₅₀ concentrations of each insecticide under laboratory conditions. Sublethal treatments significantly affected developmental time, longevity, fecundity, and overall population fitness. The total pre-adult duration increased from 11.66 days in the control to 18.07 days under deltamethrin LC₅₀ exposure. Adult longevity decreased from 18.06 days in the control to 11.52, 13.92, and 14.18 days for deltamethrin, cypermethrin, and chlorantraniliprole LC₅₀, respectively. Fecundity was severely reduced, declining from 57.69 nymphs per female in the control to 10.63, 21.57, and 28.92 at LC₅₀ of the respective insecticides. Demographic analysis showed that the intrinsic rate of increase (<i>r</i>) and finite rate of increase (<i>λ</i>) significantly decreased with increasing concentration. The control population exhibited <i>r</i> = 0.346 day^-1 and λ = 1.413 day^-1, whereas these values dropped to 0.097 and 1.101 under deltamethrin LC₅₀, 0.165 and 1.179 under cypermethrin LC₅₀, and 0.198 and 1.219 under chlorantraniliprole LC₅₀. Conversely, mean generation time (<i>T</i>) increased from 11.66 to 18.07 days. Overall, deltamethrin caused the most severe demographic suppression, followed by cypermethrin and chlorantraniliprole. These findings demonstrate that sublethal insecticide exposure can markedly disrupt the life history and population growth of <i>R. padi</i>, underscoring the necessity of integrating sublethal effect evaluations into ecological risk assessment and IPM programs.