Risk Assessment Of Resistance To Buprofezin And Laboratory Screening Of Alternative Insecticides For Replacing Highly-Toxic Insecticides For Controlling The White-Backed Planthopper, Sogatella Furcifera (Horv(?)th)

The white-backed planthopper is one of important insects in rice-growing countries around the world.It also damages rice- raising in our country.Because of t great potential reproduction,the number of the white-backed planthopper increased quickly even to outbreaks easily.It is typical r-strategy pest.As emergency measures in management, insecticides play important role in controlling the pest.Laboratory screen of alterative insecticides for replacing highly-toxic organophosphate insecticides for controlling the white-backed planthopper,Comparing the toxicity of 8 insecticides to the white-backed plantopper population from Nauning city of Autonomous region of Guangxi,in 2006 and 2007,were conducted in this study.In addition,the field population of S.furicifera from jiangpu in Nanjing was selected continuously with buprofezin for 15 generations and risk assessment to buprofezin was conducted. Cross-resistance in S.furicifera against buprofezin to 6 insecticides was also investigated. This study provides scientific basis and directions for controlling S.furicifera by insecticides and preventing or slowing the course of resistance to buprofezin.The results were summarized as follows:1.Laboratory screen of alterative insecticides for replacing highly-toxic or insecticides for controlling the white-backed planthopper,S.furiciferaRice-stem dipping method was used to measure the toxicity of 20 insecticides which represented 6 different classes for theirs activities against the third nymphae of white-backed planthopper from Nanning city of Autonomous region of Guangxi in2006. The results showed that buprofezin,imdacloprid,thiamethoxam,nitenpyram,acetamiprid, butylene-fipronil,fipronil,chlorpyrifos,isoprocarb and dichlovos had relative high toxicity to Nanning population(Guangxi).Based on this data,the above 11 insecticide among 5 different classes have potential to be adopted as alternatives for replacing the high toxic pesticides. 2.Comparing the toxicity of 8 insecticides to the white-backed plantopper population from Nanning city of Autonomous region of Guangxi,in 2006 and 2007Rice-stem dipping method was used to measure the toxicity of 20 insecticides to Nanning population(Guangxi) in 2007.Comparing with the data in 2006,it suggested that the susceptibility of S.furicifera in 2007 to fpronil,nitenpyram and acetamiprid changed largely.Because of 95%confidence limit of acetamiprid overlapping,the changing to acetamiprid is not marked.The changing to the other insecticides is not changed.3.Laboratory screen of insecticide-mixture for controlling the white-backed planthopperThe co-toxicity of butylene-fipronil mixed with buprofezin,imdacloprid, thiamethoxam,Chlorpyrifos in different ratios was assayed by Rice-stem dipping method against the third instar nymphae of the white-backed planthopper,The results showed that five mixtures have synergism effect.The co-toxicity of butylene-fipronil mixed with buprofezin in the ratio of 3:1 and 5:1 is 212.0437 and 191.4021.The value of LC₅₀ of the ratio of 3:1 is minimum,so it is the best ratio.The co-toxicity of butylene-fipronil mixed with imdacloprid in the ratio of 1:5 and 5:1 is 210.5552 and 218.1364.The value of LC₅₀ of the ratio of 1:5 is minimum,so it is the best ratio.The co-toxicity of butylene-fipronil mixed with chlorpyrifos in the ratio of 5:1 is 188.3963.4.Risk assessment of S.furicifera to buprofezinA field population was collected in 2006 from Nanjing(Jiangsu),and was selected continuously with buprofezin for 15 generations with LC₅₀ increased 9.61 folds compared with the original reference strain.Realized heritability(h²) for entire selections was 0.2754, suggesting a higher risk of resistance to buprofezin.The 10-folds increase in LC₅₀ to buprofezin was expected in 4～5 generations.These results demonstrated S.furicifera may have a higher risk of resistance to buprofezin.So it is important and key to offer reasonable plan for chemistry controlling S.furicifera and prevent the course of resistance to buprofezin.