Abstract: 【Aim】 This study aims to evaluate the biological activities of four components of essential oils, namely eugenol, α-terpineol, cinnamon oil and citronella oil, to the wolfberry aphid (Aphis gossypii), and the effect of diethyl maleate and ethyl salicylate on the toxicity of these compounds to A. gossypii, so as to provide a scientific basis for more effective and green ways to prevent and control insect pests of the Chinese wolfberry, Lycium spp. 【Methods】 The repellent activity of the above four component compounds of essential oils to apterous adults of A. gossypii originated from Chinese wolfberry were tested by dichotomous choice method. The toxicity of these compounds to A. gossypii adults was evaluated by the method of residual film in glass tube. The in vitro activities of acetylcholinesterase (AChE) and adenosine triphosphatase (ATPase) of A. gossypii adults treated with these compounds were tested by bicochemical analysis. 【Results】 α-Terpineol (1%) showed remarkable repellency to apterous adults of A. gossypii, with the repellent rates of 58.1%, 58.6% and 55.7% at 1, 2 and 3 h after treatment, respectively. The repellent rate of the four compounds against A. gossypii adults at 3 h ranked in the descending order as α-terpineol>citronella oil>cinnamon oil>eugenol. Eugenol showed the highest toxicity to A. gossypii adults, with the LC₅₀ value of 0.48 mL/L at 4 h post treatment, while the LC₅₀ values of cinnamon oil, α-terpineol and citronella oil to A. gossypii adults were 1.23, 6.24 and 11.97 mL/L, respectively. The bioassay results against A. gossypii adults showed that the synergistic ratios of diethyl maleate to citronella oil, cinnamon oil, eugenol and α-terpineol were 2.75, 2.86, 1.78 and 1.56, respectively, while those of ethyl salicylate to citronella oil, cinnamon oil, eugenol and α-terpineol were 3.41, 2.67, 2.00 and 1.89, respectively. The toxicity ratios showed that the toxicities of the four compounds to A. gossypii adults had 49.9-fold difference. Eugenol mixed with diethyl maleate or ethyl salicylate showed the highest contact toxicity to A. gossypii adults. The four compounds tested had different effects on the activities of AChE and ATPase of A. gossypii adults. Eugenol had an inhibitory effect on AChE activity, but enhanced the ATPase activity at low concentrations and inhibited the ATPase activity at high concentrations. 【Conclusion】 α-Terpineol has high repellent activity against A. gossypii adults. The toxicities of eugenol, α-terpineol, cinnamon oil and citronella oil against A. gossypii adults differ much. Eugenol after mixed with diethyl maleate or ethyl salicylate shows enhanced toxicity to A. gossypii adults and may be a potential agent for controlling aphids. The tested four components of essential oils have certain inhibitory effects on the in vitro activities of AChE and ATPase of A. gossypii adults.

Key words: Aphis gossypii, essential oil, component, toxicity, repellent activity, enzymatic activity, synergist