الفهرس 
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Abstract
The Egyptian cotton leafworm, Spodoptera littoralis one of the most destructive agricultural lepidopterous pests. Bioassays were conducted to study the toxicity of indoxacarb, pyridalyl, and chlorpyrifos against Spodoptera littorals and the efficiency of the tested insecticides under field conditions. The effects of mustard oil and neem oil were investigated as an alternative to chemical insecticides to control this insect. The effects of tested insecticides in some physiological and biological aspects in 2nd and 4th instar larvae of S. littorals after treatment were also studied. Based on the obtained LC50 values, plyridalyl was the most effective compound followed by chlorpyrifos and indoxacarb. The LC50 values in the 2nd instar larvae were 0.067, 0.23, and 3.42 ppm, but the LC50 values in the 4th instar larvae were 0.236, 0.69, and 7.79 ppm, respectively. Neem oil was more toxic than mustard oil against S. littorals. The LC50 values of mustard oil and neem oil against 2nd instar larvae were 7.99 and 1.94%, but in the 4th instar larvae were 2.86 and 20.30%, respectively. Under field conditions, all investigated insecticides at the recommended concentrations reduce infestation of S. littoralis on cotton plants compared to the control. Chlorpyrifos was the most effective insecticide followed by, Plyridalyl and indoxacarb. There is a difference in some biochemical aspects (total soluble protein, lipid contents, carbohydrate hydrolyzing enzymes activity, AST and ALT enzyme activity) between treated groups with tested insecticides and the control group. Changes in some biological aspects in treated groups were also noticed.