Abstract: 【Objective】To study insecticidal mechanism of terpinen-4-ol, the main insecticidal composition in essential oil of Sabina vulgaris. 【Method】The 5th instar larvae of the Mythimna separta were treated by terpinen-4-ol with topical application. The activities of phosphatase , glutathione S-transferase （GSTs）, cytochrome P450 （P450） and polyphenol oxidase（PPO）of insects tested were determined in all poisoning stages .【Result】The activities of both acid phosphatase (ACP) and alkaline phosphatase (AKP) in insects treated were induced by terpinen-4-ol, but ACP was inhibited in paralysis stage. The activities of GSTs were inhibited in exciting stage, convulsing stage and paralysis stage, but gradually recovered in recovering stage. O-demethylase activity of cytochrome P450 was inhibited by terpinen-4-ol, the inhibit rate in all poisoning stages were26.27％、 46.03％、 80.24％ and 90.22％ respectly. PPO activities was strong inhibited by terpinen-4-ol, both in vitro and in vivo. 【Conclusion】The activities of P450, GSTs and PPO probably had relation with toxicity of terpinen-4-ol against larvae of the Mythimna separta, but the toxic insects recovering probably related to GSTs induced. As a kind of new insecticide or synergist, terpinen-4-ol has potential value in insecticide resistance management.

Key words: Terpinen-4-ol, Mythimna separata, Polyphenol oxidase（PPO）, Metabolizing enzymes, Insectical mechanism