Abstract:  To understand the physiological mechanism of insecticide-induced enhancement of flight capacity of the brown planthopper, Nilaparvata lugens (Stål), we examined the changes of trehalose content and the trehalase activity in the 3rd and 5th instar nymphs and the adults of N. lugens under the stress of sublethal dose of three insecticides (imidacloprid, triazophos and deltamethrin).The results showed that the trehalose content and the trehalase activity in the 3rd instar nymphs treated with three insecticides were not significantly different from those of the control (P>0.05). The trehalose content in the 5th instar nymphs treated with 40 mg/L triazophos was significantly lower than that in the control (P<0.05), decreased by 24%, while the trehalase activity in the 5th instar nymphs treated with 20 and 40 mg/L triazophos was significantly higher than that in the control (P<0.05), increased by 100% and 129%, respectively. Compared to the controls, the trehalose content in brachypterous female and male adults was significantly reduced in treatments of 10 mg/L imidacloprid, 20 and 40 mg/L triazophos, and 3 and 6 mg/L deltamethrin (P<0.05), decreased by 36%, 53%, 67%, 58% and 69% in female adults, and 59%, 71%, 65%, 70% and 77% in male adults, respectively. However, the trehalase activity in brachypterous female and male adults was significantly increased in treatments of 40 mg/L triazophos and 3 and 6 mg/L deltamethrin, compared to the controls (P<0.05), increased by 124%, 100% and 88% in female adults, and 146%, 132% and 118% in male adults, respectively. The trehalose content in macropterous female and male adults treated with 10 mg/L imidacloprid, 40 mg/L triazophos and 3 mg/L deltamethrin was significantly lower than that in the control (P<0.05), decreased by 44%, 34% and 37% in female adults, and 48%, 54% and 43% in male adults, respectively. However, the trehalase activity in macropterous female and male adults treated with 5 and 10 mg/L imidacloprid, was significantly higher than that in the control (P<0.05), increased by 170% and 97% in female adults, and 317% and 300% in male adults, respectively. The results suggest that the trehalase activity of N. lugens is increased by treatments of sublethal dose of the three insecticides, while the trehalose content is reduced. The present work provides some valuable clues for understanding the mechanism of insecticide-induced enhancement of flight capacity of the N. lugens.

Key words:  Nilaparvata lugens, insecticide, sublethal dose, trehalose, trehalase, energy substance, flight capacity