Effect of certain insecticides on the biological aspects of cotton leaf worm, Spodoptera littoralis (Boisd.) (Lepidoptera: Noctuidae) under laboratory conditions.

The effect of four insecticides including emamectin benzoate (Surrender), chlorantraniliprole (Coragen), novaluron (Roxy) and methomyl (Goldbeen) against 4th instar larvae of laboratory and field strains of Spodoptera littoralis, and the latent effect of their LC50s on larval metamorphosis were studied under laboratory conditions. The 4th instar larvae were fed for 24 hrs. on castor bean leaves (Ricinus communis L.) treated with different concentrations of the tested compounds. The obtained results indicated that emamectin benzoate was the most potent among the tested insecticides on 4th instar larvae of S. littoralis with LC50 values of laboratory strain were 0.025, 4.09, 4.21 and 6.67 ppm for emamectin benzoate, chlorantraniliprole, novaluron and methomyl, respectively and the LC50 values of field strain were 1.12 ppm, 6.88 ppm, 13.35 ppm and 102.63 ppm for emamectin benzoate, novaluron, chlorantraniliprole, and methomyl, respectively. The latent effect changed according to the strain and compound; both strains treated larva highly affected. Therefore, larval and pupal durations and pupae and moths malformations and sterility % were increased, however pupation %, adult emergence %, fecundity, hatchability and longevity were decreased. Novaluron insecticide had the highest effect on the tested biological aspects compared with control in laboratory strain. Additionally, chlorantraniliprole and novaluron had the greatest effect on fecundity and hatchability of field strain. However, emamectin benzoate had the highest effect on both adult longevity and pupal duration of field strain, while novaluron decreased the larval duration. These findings admitted that novaluron is more effective than other compounds for controlling S. littoralis.