[Toxicity of Vitex negundo extract to aphids and its co-toxicity with imidacloprid].

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 LC50 of V. negundo seed dichloromethane extract to A. citricola, A. gossypii, and M. persicae was 334.59, 362.79, and 2685.8 mg x 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 1000:1, 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%-33.68% after treated for 24 and 48 hours.