Chitosan Efficacy against the Cotton Leaf Worm Spodoptera littoralis (Boisd.) (Lepidoptera: Noctuidae)

Chitosan is a derivative of chitin naturally occurring compound and became of great interest not only for its medical utilities but also as an alternative to chemical insecticides. Insecticidal activity of chitosan was investigated against the 4th larval instar of the cotton leaf worm Spodoptera littoralis (Boisd.) under laboratory conditions. Results showed that the percent mortality increased with increasing chitosan concentration. LC50 was 734.923ppm. Marked changes were recognized in some enzymatic activity when chitosan was applied at the LC50 level. Significant decrease was recorded in the levels of protease, invertase, phenoloxidase, chitinase and acetylcholinesterase activities. On the other hand, acetylcholine concentration increased after chitosan application. These findings suggest that chitosan caused physiological disturbance in S. littoralis larvae and may be used in IPM programs for controlling this pest.