Abstract:  In order to study the insecticidal activity and toxicity mechanism of α-terpineol, a plant volatile organic compound, we tested the acute toxicity of α-terpineol against the 4th instar larvae of Zophobas morio in a gas-fumigation system and investigated the in vivo activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) in the treated larvae at different fumigation duration. The results showed that the LC₅₀ and LC₂₀ values of α-terpineol against the 4th instar larvae in acute toxicity test at 48 h after fumigation were 69.425 μg/L and 59.916 μg/L, respectively. Under the fumigation of α-terpineol at two concentrations (LC₅₀  and LC₂₀ ), the activities of SOD, POD and CAT showed a time-course change, first increasing and then decreasing. It is so inferred that the gradual accumulation of α-terpineol in the treated larvae produces significantly negative effects on the activities of SOD, POD and CAT in their bodies, and this may lead to a decline in scavenging activity of free radicals and stronger toxic effects on Z. morio larvae.

Key words: Zophobas morio, α-terpineol, fumigation, acute toxicity, protective enzymes, enzyme activity