Monitoring Of Insecticide Resistance, Resistance Risk Assessment And Biochemical Mechanism For Buprofezin In Nilaparvata Lugens(St(?)l)

The brown planthopper Nilaparvata Lugens (Stal), one of the major migratory insects on rice in Asia, often occurred frequently in Southweast areas, Southern areas, Yangtze River Dalta areas and Jianghuai areas in China. Currently, chemical control is still a major method for suppressing N. lugens. With the forbidden using of fipronil and stopping using of imidacloprid, buprofezin became the major insecticides for controling N. lugens again. Therefore, it was important to assess the resistance risk, cross resistance and biochemical mechanism of buprofezin, at the same time monitoring the resistance change of insecticides and finding out the susceptible insecticides in N. lugens was very neccessary. The results could provide basis for insecticide resistance management of the brown planthopper, N. lugens.1 Insecticide resistance detection and monitoring in N. lugens.In order to design the management strategies of control N. lugens, it is necessary to know the current situation of resistance of N. lugens to conventional insecticides. The resistance of 7 insecticides of field populations of N. Lugens from different localities were carried by rice dipping methods from 2009 to 2010. The results showed that substantial variations of the resistance level to different insecticides existed in N. lugens. Field populations developed low to medium level (RR=9.0-14.0 fold) and medium to high level (RR=6.0-48.9 fold) to buprofezin, respectively. High or extremely high resistance level still kept to imidacloprid (RR=152.8-710.7 fold). For insecticides such as thiamethoxam, chlorpyrifos and butene-fipronil, the resistance ratios were in the range of 4.1-24.7 fold, 1.3-7.3 fold and 2.4-22.4 fold, respectively. Field populations were still susceptible to pymetrozine (RR=0.9-4.6 fold) and susceptible to low resistance level to nitenpyram (RR= 1.1-6.1 fold).2 Resistance risk assessment of buprofezin resistance in N. lugens.To assess the resistance risk of buprofezin, Haiyan population collected in 2007 was continuously selected in laboratory. After 10 generations, the resistance ratio increased from 11.7 to 2788.1 fold (the LC50 value from 0.82 mg/L to 195.17 mg/L), with the ratio increased by 238.3 fold. The estimate of realized heritability (h2) of 1-10 generation was 0.6404. The result showed that continuous selection with buprofezin could further increase the resistance level when a mid-resistance level had already developed in the population.3 Biochemical mechanism for buprofezin resistance in N. lugensSynergism experiment with TPP, PBO and DEM was performed to survey the roles of detoxication enzymes in buprofezin resistance strain of N. lugens. The results showed TPP had significant synergistic effect on buprofezin toxicity in the resistant strain (SR=2.4), but no effect in the susceptible strain and the initial strain. PBO had significant synergistic effect on buprofezin toxicity in all the three strains, and DEM had no obvious synergism in three stains of N. lugens. Enzyme activity assay demonstrated that the resistant strain had higher activity of esterase than initial strain (Ratio=4.2 fold). For cytoehrome P450-monooxygenases and glutathione S-trsnsferase activity, no difference was found between resistant strain and initial strain (Ratio=1.6 and 0.7 fold respectively). It indicated that esterase worked in buprofezin resistance, and cytoehrome P450-monooxygenases and glutathione S-trsnsferase didn't play a role in buprofezin resistance.4 Cross-resistance of buprofezin in N. lugensCross-resistance of buprofezin to other insecticides in resistant stain of N. lugens was determined by rice dipping methods in laboratory. The results indicated that buprofezin resistant stain showed no cross resistance to chlorpyrifos, butene-fipronil, imidacloprid and ethiprole, and it maybe had low level negative cross-resistance to thiamethoxam. Therefore, according to the resistance of N. lugens field pupolation to buprofezin had reached medium to high level, chlorpyrifos, thiamethoxam and butene-fipronil(no register in rice) could be used alternating and rotating with buprofezin to control N. lugens in the resistance management program.