Detoxification System in Spodoptera littoralis against Abamectin

Biochemical and histological analysis were performed on 4 larval instar of the cotton leaf worm Spodoptera littoralis to determine the effect of abamectin (LC50) on the biomarkers acetylcholinesterase (AChE), glutathione S-transferase (GST), α-, βesterase and mixed function oxidase (MFO).Biochemical analysis showed a severe reduction in the enzymatic activities of GST and α-esterase, as compared to the control, reaching their minimum activity at 4-day post-treatment. Therefore, abamectin may be not detoxified by these enzymes.Abamectin increase the enzyme activity of βesterase reaching its maximum activity at 4-day post-treatment. Abamectin treatment resulted in slightly reduction in MFO activity at 2and 6-day post-treatment, while it has no effect on the enzyme activity of AChE at all-time intervals, as compared with control. The natural bio-pesticideis being tested here with reference to insect hemocyte count (THC) and ultrastructure.Two days after treatment THC increased by 1.7-fold, whereas decreased after 4 and 6 days of application by 1.3 and 1.6-fold, respectively, as compared to untreated controls. Histological study on the S. littoralis larval hemocytes showed that abamectininduced pathological detrition. Electron dense granules, structured granules and desmosomes were synthesized. Also, large number of deformed mitochondria, autophagic lysosome and long pseudopodia were observed in hemocytes treated with abamectin. Finally, at late stage of infection cell organelles were completely lysed.