| Nilapavata lugens(Stal) and Chilo suppressalis (Walker) are two major pests of rice. The frequent outbreaks of these pests in recent years lead to serious losses of rice yield in China. In this study, we determined the toxicity of several kinds of individual insecticides to Nilapavata lugens and Chilo suppressalis, respectively. And then the ideal mix-proportions of insecticides combination which had maximum synergetic action was screened through the base of co-toxicity coefficient evaluating joint action of two insecticides to Nilapavata lugens. Also, we described a rapid detection method of insecticide resistance in Nilapavata lugens and Chilo suppressalis. The main results are as follow:1. Toxicity determination of six individual insecticides to Nilapavata lugensThe toxicity of six individual insecticides to Nilapavata lugens was measured by rice seedling dipping method in laboratory. The results showed that the toxicity of nitenpyram was the highest and the value of LC50was0.12mg/L. Toxicity of other5kinds of pesticides from high to low in turn to avermectins (1.43mg/L)> buprofezin (1.85mg/L)> lambda-cyhalothrin (4.63mg/L)> chlorpyrifos (4.71mg/L)>pymetrozine (22.46mg/L).2. Toxicity determination of mixtures of two individual inseetieides to Nilapavata lugens and optimum mix proportion screeningRice seedling dipping method was used to test the joint toxicity of avermectins and nitenpyram, avermectins and buprofezin to Nilapavata lugens. The optimum proportion of combination insecticides between avermectins and nitenpyram was screened in door, the results showed that proportion of5:5of mixture was response to the maximum CTC value of215.40and had maximum synergetic action. The ideal mix-proportion of avermectins and buprofezin was7:3, and that the maximum CTC value was294.00.3. Toxicity determination of five individual insecticides to Chilo suppressalisWith dipping-insect method, toxicity test among five kinds of insecticides in door to Chilo suppressalis was carried out. The results showed that avermectins had the highest toxicity and value of LC50was0.17mg/L. Toxicity of other4kinds of pesticides from high to low in turn to lambda-cyhalothrin (4.75mg/L)> chlorantraniliprole (8.74mg/L)> bisultap (85.32mg/L)> chlorpyrifos (86.44mg/L).4. Study on the pesticides selection kitDiagnostie dose of nitenpyram on Nilapavata lugens and chlorpyrifos on Chilo suppressalis were determined with the residual film method in the lab. According to the bioassay results of rice seedling dipping method and dipping-insect method, the LC99value of toxicity of nitenpyram was11.60mg/L, that for chlorpyrifos was1991.10mg/L. Potency of the kit of pesticides treated in different conditions was also measured, results showed that in25℃and30℃,35℃condition, the mortality had no significant difference. The potency of nitenpyram and chlorpyrifos in glass bottle can last only for1day under the condition of25℃and lightless. |
