Comparative Physiological Studies On Cotton Leafworm Spodoptera Littoralis:

Amira Mohamed El-sayed El-shewy?

The present study aimed to evaluate the effect and the insecticidal activity of some tested compounds such as the bacterial formulation protecto (B. thuringiensis var kurstaki), the chemical insecticide (lannate) and the plant extracts namely (coumarin & azadirachtin) against the 4th instar larvae of the cotton leafworm, S. littoralis.This study aimed to evaluate:1.The antifeedant activity of tested compounds against 4th instar larvae of the cotton leafworm , S. littoralis2.Insecticidal and some biological aspects of S. littoralis such as larval mortality, larval duration, percentage of pupation, pupal duration, percentage of adult emergence and sex ratio. Also, malformation of pupae and adults, egg deposition, hatchability percentage and sterility percentage.3.The histopathological effect of tested compounds on the mid gut of treated larvae.4.The effect of tested compounds on total soluble protein, carbohydrate hydrolyzing enzymes, transaminase (GPT&GOT), alpha & beta esterase, acid & alkaline phosphatase and acetylcholinesterase enzyme.The results may be summarized as follows: I. Antifeedant activity:Out of 4 different tested compounds with regard to antifeedant effects against 4th instar larvae of the cottonleafworm larvae, data indicated that the plant extracts coumarin and azadirachtin recorded the highest antifeedant activity while insecticides lannate and protecto gave the lowest antifeedant activity. Coumarin recorded the highest mean of antifeedant activity reached (69.07) followed by azadirachtin (58.17), lannate (48.15) and protecto (19.50), respectively.II. Insecticidal activity::Data indicated that the chemical insecticide, lannate had the superior insecticidal activity followed by coumarin, while azadirachtin showed moderate activity. On the other hand protecto showed lower larvicidal activity. The tested compounds could be arranged according to their larvicidal activities against the cotton leafworm larvae based on LC50 in the following descending order:Lannate (13.72 ppm), < protecto (0.39 g/100 ml),