Abstract: To study the acaricidal mechanism of the fraction L1-2, the main acaricidal component in the extracts of Arctium lappa L.【Methods】The female Panonychus citri （McGregor） adults were treated by the fraction L1-2 with contact application. The activities of carboxylesterase （CarE）, acetylcholine esterase （AChE） and glutathione S-transferases （GSTs） in mites were determined at all poisoning stages.【Results】The CarE activity was inhibited at the stillness stage and the recovery stage, but was induced at the other stages. The activities of AChE and GSTs were induced at all poisoning stages but the stillness stage, and strongly enhanced at the convulsion stage and the paralysis stage, then gradually recovered at the paralysis stage and the recovery stage. 【Conclusions】The CarE activity is related with toxicity of the fraction L1-2 against the female P. citri adults, but the recovery of poisoned mites is probably due to the GSTs and AChE activities induced. L1-2 fraction can affect not only the nerve transition but also the digestive and reproductive system of mites in a long time, so it has potential value in acaricidal research and development.

Key words: Panonychus citri, Arctium lappa, acaricidal mechanism, metabolic enzymes, acaricidal activity