Effect of Azadirachtin on Ecdysone 20-monooxygenase of Spodoptera litura (Fabr.) (Noctuiidae; Lepidoptera)

Effect of azadirachtin (1 μg g⁻¹ body weight) on ecdysone 20-monooxygenase activity of Malpighian tubules, fat body and midgut tissues of sixth instar Spodoptera litura (F.) was studied dsing thin layer chromatography and liquid scintillation spectroscopy techniques. The highest activity of the enzyme was observed at the beginning of the final instar larva (24h) which decreased with the advancement in age. In in vivo condition, treated larvae showed a marginal decrease in the activity of the enzyme. However, under in vitro, condition azadirachtin caused a dose dependent inhibition of ecdysone 20-monooxygenase activity.