Effect of Achillea millefolium and Teucrium polium extracts on nutritional indices and α-amylase and protease activities of Egyptian cotton leafworm, Spodoptera littoralis (Lepidoptera: Noctuidae)

The effect of methanolic extracts of Achillea millefolium and Teucrium polium on third instar larvae of Egyptian cotton leafworm, Spodoptera littoralis were investigated. Methanolic plant extracts were mixed with artificial diet and then nutritional indices, glutathione-S transferase, esterase, α-amylase and protease, activity were measured 72h later. Approximate digestibility was increased significantly in larvae fed on the food containing methanolic extract of T. polium but there was not any significant change in insects treated with A. millefolium. T. polium significantly decreased relative growth rate (RGR), relative consumption rate (RCR), efficiency of digested food (ECD) and efficiency of conversion of ingested food (ECI) whereas A. millefolium only decreased RGR and RCR. Feeding on artificial diet containing plant extract decreased α-amylase and protease activities in the midgut of the insect. Furthermore, the effect of methanolic extract of plants on detoxifying enzymes showed that they have no effect on glutathione S-transferase and esterase activities.