Abstract:

In order to reveal the insecticidal activity and mechanism of cantharidin, the effect of cantharidin on activities of carboxyl esterase (CarE), phosphatases, glutathione S-transferase (GST), O-demethylase of cytochrome P450 and PPO in larvae of  Mythimna separata (Walker) were assayed. The results showed that CarE in the treated insects was distinctly activated and at 48 h after treatment their specific activity was 1.68 times that of the control. ACP activity showed no distinct change at 6 h and 12 h after treatment, but was activated at 24 h after treatment and significantly different from the control (P＜0.05). The activity of alkaline phosphatase (ALP) was inhibited obviously, and the inhibition became more intensive as the exposure time prolonged. The activity of O-demethylase was first inhibited, and then activated. GST activity was first activated, and then inhibited. PPO activity was strongly inhibited by cantharidin both in vitro and in vivo. It is so inferred that catharidin can affect the metabolic enzymes distinctly, and the inhibition on ALP and PPO may be related to its toxic effect.

Key words: Mythimna separata, cantharidin, metabolizing enzymes, polyphenol oxidase (PPO), insecticidal mechanism