Abstract: In order to study the insecticidal activity and toxicity mechanism of α-pinene(a plant volatile organic compound), we tested the acute toxicity of α-pinene against 4th instar larvae of Zophobas morio in a gas-fumigation system, and investigated the activities of carboxylesterase (CarE), acid phosphatase (ACP), alkaline phosphatase (ALP) and the glutathione S-transfer (GSTs)in the larvae at different fumigation time. The results showed that the acute toxicity LC₅₀ and LC₂₀ values of α-pinene against the 4th instar larvae in 48 h were 21.435 and 12.140 μg ·L^-1, respectively. Under the fumigation with LC₅₀ and LC₂₀ concentrations (21.435 and 12.140 μg ·L^-1) of α-pinene, the activity of CarE was significantly inhibited. The activities of ALP and GSTs first increased but subsequently reduced. Under the fumigation at LC₂₀ concentration of α-pinene, the activities of ACP was increase. Under the fumigation at LC₂₀ concentrations of α-pinene, the ACP activity showed first increased but subsequently reduced. It could be inferred from the above results that α-pinene had a high biological activity on Z. morio, which could effectively interference the detoxifying enzymes, disrupt the normal physiological metabolism and show high toxicity effect on the insect.

Key words: α-pinene, Zophobas morio, acute toxicity, detoxifying enzymes