Abstract: In this paper, the toxicity of Vitex negundo seed dichloromethane extract, imidacloprid, and omethoate to Aphis citricola, Aphis gossypii, and Myzus persicae was determined by impregnation method, and the co-toxicity of the seed extract and imidacloprid to A. gossypii as well as the repellent effect of the extract and test insecticides to M. persicae were tested by topical application of capillary tube and by selection in culture dish, respectively. The results showed that the LC50 of V. negundo seed dichloromethane extract to A. citricola, A. gossypii, and M. persicae was 33459, 36279, and 26858 mg·L-1, respectively, indicating that V. negundo seed dichloromethane extract was highly toxic to A. citricola and A. gossypii. The co-toxicity coefficient of the seed extract and imidacloprid was 17745 when the mixture was in 1000 ∶〖KG-*2〗1, showing an obvious synergism. The repellent effect of V. negundo seed dichloromethane extract and imidacloprid to M. persicae was 5575% and 3944%, and 6989% and 6543% after treated for 24 and 48 hours, respectively, while that of thiamethoxam and acetamiprid to M. persicae was 1652%〖KG-*2〗-〖KG-*7〗3368% after treated for 24 and 48 hours.

Key words: relative importance value, functional group diversity, species diversity, community stability