Effects of some Insecticides on some Biological Parameters of Cotton Leafworm, Spodoptera littoralis (Lepidoptera: Noctuidae)

Toxicity and sublethal effects of fipronil, chlorantraniliprole, emamectin benzoate and novaluron against the 2nd instar of Spodoptera littoralis larvae after 24 and 48 hrs were evaluated. The LC_5 values after 48 hrs of exposure were 0.062, 0.0008, 0.0001 and 0.048 mg L^-1 for fipronil, chlorantraniliprole, emamectin benzoate and novaluron, respectively. While LC_10 values after 48 hrs of exposure were 0.097, 0.0013, 0.0002 and 0.027 mg L^-1, respectively. Treated 2nd instar of S. littoralis larvae by LC_5 and LC_10 values of fipronil, chlorantraniliprole, emamectin benzoate and novaluron showed significant (P 0.05) reduction in larval body weights, larval duration, % pupation, pupal mean weight and % adult emergence rates. However, the average time to the pupation (pupal duration) for larvae treated did not change significantly in all treatments compared to control. Fecundity, fertility and adult longevity were strongly or softly reduced in all insecticide treatments compared to control. These results suggest that sublethal concentrations of the tested insecticides may reduce the population growth of S. littoralis by affecting the development and reproduction.