Abstract: In insects, carbohydrates play an important role in both energy metabolism and material synthesis. The main purpose of the present study is to evaluate the effects of four compounds (scopolamine hydrobromide, nicotine, esculin and saponin) on trehalase activity and content of related carbohydrates in larvae of the cotton bollworm, Helicoverpa armigera (Hübner). The results showed that at 96 h after treatment in larvae with saponin, the larval growth was significantly inhibited, and the mortality was enhanced with the increasing saponin concentration. At the dosages of 10, 20, 40 g/L saponin, the mean weights of larvae were 0.194, 0.089 and 0.034 g, being 86.99%, 39.91% and 15.24% of the control, respectively. According to the determined trelalase activity as well as the activities of related metabolic enzymes, β-glucosides significantly inhibited the trehalase activity in the midgut while alkaloid inhibited the trehalase activity in the haemolymph and fat body obviously. Trehalase activity in the midgut was about 54.21% of the control at 96 h after the larvae were exposed to saponin at the dose of 40 g/L, while 83.73% of the control after the larvae were exposed to esculin at the dose of 30 g/L. Trelalase activities in both the hemolymph and fat body were 7.24% and 71.43% of the control, respectively, at 96 h after the larvae were exposed to scopolamine hydrobromide at the dose of 20 g/L, while 26.29% and 33.44% of the control after the larvae were exposed to nicotine at the dose of 20 g/L. Trehalose activity in the hemolymph was all increased by scopolamine hydrobromide, nicotine and esculin. All the four compounds affected the activity of glycogen phosphorylase. Saponin inhibited significantly the activity of glycogen phosphorylase in the midgut and fat body. The glycogen level changed consequently in contrast to the activity of glycogen phosphorylase with the increasing of compound concentration. When the larvae fed with botanical compounds, the change of glucose content in the hemolymph was consistent with that of trehalose content, and glycogen content in fat body was all declined to some extent. The results proved that β-glucosides could inhibit the trelalase activity, and this may have reference value in developing new pesticide compounds.

Key words: Helicoverpa armigera, trehalose, trehalase, botanical compounds, glycogen, glycogen phosphorylase