Toxicity of imidacloprid, thiamethoxam, ethofenprox and their mixtures on Nilaparvata lugens in Guizhou province

The experiment was conducted to study the toxic effects of imidacloprid, thiamethoxam, ethofenprox and their mixtures on the 3rd nymph of Nilaparvata lugens in Huangpin, Kaiyang and Tongzi County, Guizhou province by topical application method. Then the synergistic prescription was selected according to the laboratory experiments by interactive measurement. The results showed that the LD50 of imidacloprid, thiamethoxam, ethofenprox and their mixtures on N. lugens in three districts were 0.00125-0.00175 μg/headage, 0.00135-0.00169 μg/headage and 0.01739-0.01850 μg/headage, respectively. Compared with the susceptible strain of N. lugens, the populations developed moderate level of resistance to imidacloprid(resistance ratios were 19.9-24.9), and was sensitive to ethofenprox. And the toxicity measurement indicated that the mixtures of imidacloprid and ethofenprox(1 ∶5), thiamethoxam and ethofenprox(1 ∶7) had excellent synergistic effect on N.lugens, the co-toxicity coefficients(CTC) were 166.93-198.23 and 174.29-188.74,respectively. The results could provid the scientific basis for choosing the better insecticides, guiding insecticides mixed and the development of preparation.