Biochemical effects of three insect growth regulators against cotton leafworm, <i>Spodoptera littoralis</i> (Lepidoptera: Noctuidae)

Abstract

The current study was carried out to evaluate the biochemical effects of 4^th and 6^th instar larvae of S. littoralis provided with treated castor bean leaves for three different insect growth regulators (IGRs) (Novaluron, Pyriproxyfen, and Cyromazine). To determine the effect of these IGRs on total protein, total carbohydrate, total lipids, the activity of chitinase, the activity of acetylcholinesterase and carbohydrates hydrolyzing enzymes (Amylase, invertase, and trehalase activities) at LC₅₀ concentrations of this treatment. The results showed that total proteins, lipids, and carbohydrate content were significantly decreased with all tested IGRs, except for an increase in total carbohydrates with Novaluron and Cyromazine for the 6^th instar larvae of S. littoralis. Cyromazine induced a significant decrease in chitinase activity, followed by Pyriproxyfen then Novaluron. The tested IGRs significantly increased the acetylcholinesterase activity. A significant decrease in the activity of amylase and Invertase activity was induced by the tested IGRs, except with Novaluron for 6^th instar larvae in the case of amylase and increased with all treatments for 6^th instar larvae of Invertase, in contrast, all tested IGRs led to an increase in the activity of Trehalasec except Cyromazine decreased the enzyme activity.