Study On The Susceptibility Of Several Kinds Of Insecticides And Rapid Detection Of Insecticide Resistance In Rice Planthopper

Brown planthopper, Nilaparvata lugens (Stal) and whitebacked planthopper, Sogatella furcifera (Horvath) are two important long-distance migration insect pests that cause great losses to the rice yield in China. Their occurrence area and the frequency continuous increased in late 30 years. In this paper, the resistance survey, toxicity determination of individual insecticides and mixtures of two individual insecticides to the brown planthopper, the impacts of pymetrozine on the productivity of macropterous female and a rapid detection method of insecticide resistance in rice planthopper have been described, which could be well used for reasonable management of brown planthopper resistance. Results are as follows:1. Sensitivity detection of rice planthopper to imidacloprid and buprofezinRice stem dipping method was used to detect the sensitivity of Nilaparvata lugens and Sogatella furcifera to imidacloprid and buprofezin from 2009 to 2010 in 7 field populations in Hubei province collected in Wuxue, Tianmen, Jianli, Tongcheng, Xiaogan, Gong'an and Zaoyang, respectively. Compared with the susceptible strain of Nilaparvata lugens, the populations from Hubei province had developed high level to extremely high level resistance to imidacloprid (80.2-fold to 158.9-fold in 2009 and 136.9-fold to 337.2-fold in 2010), decreased sensitivity to low level resistance to buprofezin (4.7-fold to 11.8-fold in 2009) and low-high level resistance (8.2-fold to 52.1-fold in 2010), respectively. The assay on toxicities of imidacloprid and buprofezin to the white-backed planthopper, Sogatella furcifera (Horvath) showed the seven populations remained susceptible to these two insecticides, with the LC50 values being 0.08-0.31 mg/L and 0.11-0.37 mg/L.2. Toxicity determination of individual and mixtures of two individual insecticides to Nilapai-vata lugensThe toxicity of ten individual insecticides and mixtures of two individual insecticides to Nilaparvata lugens was measured by rice stem dipping method. The results showed that the toxicity of buprofezin was the highest to Jianli population of Nilaparvata lugens in 2010, and the value of LC50 was 14.17 mg/L. The value of LC50 of monosultap was the highest with the value of LC50 303.72 mg/L. The ideal mix-proportions of phoxim and pymetrozine were screened in laboratory. The results showed that proportion of 6.40:3.80 of mixture was response to the maximum CTC value of 158.09 and had maximum synergetic action.3. The influence of pymetrozine on the productivity of Nilaparvata lugensThe influence of pymetrozine on the productivity of Nilaparvata lugens was studied. According to the bioassay results of rice stem dipping method, the LC10, LC20, LC30 of pymetrozine to Nilaparvata lugens was 2.86 mg/L,5.49 mg/L and 8.80 mg/L, respectively. Then rice plants were treated with the three concentration and the 3rd instar nymphs of Nilaparvata lugens were reared on them. The just emergent adults were reared on insecticide-free rice and divided into single Pair by long-wing types. The mean egg numbers of per macropterous female were 171.89±116.51, 140.55±65.88 and 102.11±57.91, while that of CK were 233.13±88.10. The results showed that the LC20, LC30 of pymetrozine increased very significantly the productivity of macropterous female. When applying pymetrozine to control riee pest, the productivity of Nilaparvata lugens significantly inhibited.4. Study on rapid detection of insecticide resistance in Nilaparvata lugensDiagnostic dose of isoprocarb on Nilaparvata lugens were obtained with the residual film method in the lab. According to the bioassay results of rice stem dipping method, the LC99 value of toxicity was 0.33μg/cm2, and the value of mortality was 90.56±0.57% after the 3rd instar nymphs of Nilaparvata lugens were treated with diagnostic dose of isoprocarb. Next, we will continue to study on the suitability of diagnostic dose to field population in order that the diagnostic dose method could be considered as an alternative formonitoring the resistance level of Nilaparvata lugens to insecticides.