Abstract: The effect of juvenile hormone analogue (JHA), methoprene, and 20hydroxyecdysone (20-E) on the activity of phenoloxidase in 5th instar larvae of the Asian corn borer, Ostrinia furnacalis was investigated. The activities of phenoloxidase in integument, hemolymph and hemocyte lysate of the treated O. furnacalis larvae were determined. The results showed that when larvae were treated with 1 μg methoprene and 0.1 μg methoprene, the activity of henoloxidase in integument of the larvae was higher than that of the control group (P<0.01), and the activities of phenoloxidase in hemolymph and hemocyte lysate also increased significantly (P<0.01). When larvae were reared with the artificial diet supplemented with 20-hydroxyecdysone, the activity of phenoloxidase in the integument of the larvae was lower than that of the control group (P<0.05), and the activities of phenoloxidase in hemolymph and hemocyte lysate decreased significantly (P<0.01). These results suggest that methoprene stimulates the activity of phenoloxidase, while 20-hydroxyecdysone, in contrast, inhibits the activity of phenoloxidase in O. furnacalis larvae.

Key words: Ostrinia furnacalis, juvenile hormone analogue, 20-hydroxyecdysone, phenoloxidase