Laboratory Evaluation of Some Insecticides Against Cotton Leafworm, Spodoptera littoralis (Boisd) (Lepidoptera: Noctuidae).

The toxicological effects of some insecticide mixtures (chlorpyrifos, pyridalyl, chlorantraniliprole, emamectin benzoate, and methoxyfenozide), against the 3rd instar of Spodoptera larvae were evaluated. The results indicated that, LC50 values for each insecticide were 12.44, 0.88, 0.08, 0.16 and 3.35 mg L-1 respectively, and 0.458, 0.009, 0.0014 and 0.357 mg L-1 respectively.Also, the LC50 values of chlorpyrifos are increased by larvae weight increased. LC50 values of chlorpyrifos as a function of post-feeding initiation of Spodoptera larvae to pyridalyl, chlorantraniliprole, emamectin benzoate, and methoxyfenozide after two days (single exposure) were 1.33, 1.99, 0.74, and 0.37 mg L-1 respectively. Therefore, post-feeding initiation of larvae to previous insecticides tremendously decreased LC50 values of chlorpyrifos.Also, the percent inhibition of AChE from Spodoptera head capsules by chlorpyrifos, pyridalyl, chlorantraniliprole, emamectin benzoate, and methoxyfenozide (LC10 equivalent concentrations) were 44.5, 23.4, 19.4, 33.5, and 15.4%, respectively. The percent inhibition of AChE from Spodoptera head capsules by chlorpyrifos either pre-treatment or post-treatment with pyridalyl, chlorantraniliprole, emamectin benzoate, and methoxyfenozide were increased. This indicates that the toxic potential of these pesticides for the tested organism is greater when present in a mixture than in an individual.