Study On Insecticide Sensitivity And Target Mutation Frequency Of Field Population Of Diaphorina Citri (Kuwayama)

Diaphorina citri(Kuwayama)is a dangerous pest to many rutaceae plants such as citrus,lemon and navel orange.Huanglongbing(HLB),which is transmitted by D.citri,has seriously restricted the healthy development of global citrus industry.Due to the lack of effective methods to control HLB,the control of D.Citri is the most realistic way to control the occurrence and spread of HLB.Integreted Pest Management(IPM)strategy has been advocated in the control of citrus diseases and insect pests in China.However,there are some shortcomings in the actual production,such as long prevention and control cycle,slow effect and complex operation system.Chemical control is still the main method for population control of D.Citri because of its quick effect and easy operation.Unfortunately,along with the unreasonable use of chemical pesticides,combined with the large amount of D.Citri laying eggs,short generation cycle and adaptability,etc.Field populations of D.Citri have developed resistance to many commonly used chemical insecticides,which makes effective control of D.Citri more difficult.The detection of insecticidal sensitivity of field population of D.citri has important guiding significance for formulating scientific control measures.At the same time,systematic investigation of the types,frequency,and spatial and temporal distribution of resistance genes and sensitivity genes in field pest populations is of great significance for understanding the current situation of pest resistance,formulating targeted management strategies for resistant pests,improving the effectiveness of chemical control and reducing pesticide use.In this study,the field population of D.Citri was taken as the research object,and the sensitivity of D.Citri population to 8kinds of insecticides was determined by bioassay.The mutation frequencies of major target genes in nine geographic populations of D.Citri were detected by amplicon sequencing.The main results are as follows:1.Detection of susceptibility to insecticide in field population of D.CitriThe susceptibility to imidacloprid,thiamethoxam,dinotefuran,fenpropathrin,bifenthrin,chlorpyrifos,cycloxaprid and cyantraniliprole in four field populations of D.Citri in three HLB regions(Taizhou,Zhejiang,Ganzhou,Jiangxi,Guilin and Chongzuo,Guangxi)were determined by leaf impregnation method.The results showed that the susceptibility of field populations of D.Citri varied greatly in different areas.Guilin population was most susceptible to 8 insecticides.The susceptibility of Chongzuo population to 8 insecticides was in the order of chlorpyrifos > thiamethoxam >cyantraniliprole > dinotefuran > cycloxaprid > bifenthrin > fenpropathrin >imidacloprid.The susceptibility of Chongzuo population to imidacloprid was lower than that of other populations,with LC50 value greater than 2,000 mg/L.The order of susceptibility to 8 insecticides in Taizhou population was fenpropathrin > chlorpyrifos >imidacloprid > thiamethoxam > cyantraniliprole > dinotefuran > bifenthrin >cycloxaprid.The susceptibility of Ganzhou population was similar to that of Taizhou population,but lower than that of Taizhou population to chlorpyrifos,thiamethoxam and dinotefuran.Therefore,except for the population in Guilin,the low sensitivity of the D.Citri to insecticides indicates that the field population in Chongzuo,Ganzhou and Taizhou has the potential to increase resistance.2.The mutation frequency of target resistance allele in field population of D.citriIn order to timely,accurately,quickly and conveniently detect the occurrence and development of resistance to commonly used insecticides in field populations of D.Citri.In this study,a method was developed for the first time to detect the frequency of mutated genes on D.Citri based on the amplification sequencing technology.We detected 9,150 D.Citri adults collected from major citrus producing areas and found that: The mutation frequency of the sodium channel gene VGSC＿M918T/L resistance allele associated with pyrethrin resistance ranged from 0.02 to 0.39%,and it was detected only in Taizhou and Ganzhou populations.There was no correlation between the mutation frequency of this locus and fenpropathrin resistance.The frequency of VGSC＿L925M mutation was 40.05% and 42.08% in Chongzuo population,respectively,and the frequency of L925 M mutation was 0.62% to 1.29% in Taizhou,Ganzhou,Yibin and Guilin populations.The results showed that L925 M was positively correlated with fenpropathrin resistance of D.Citri.No mutations of VGSC＿V410,T929 and F1534 were detected in any populations.For N88 S mutation of n ACh Rα1,only 0.24% and0.15% mutations were detected in male and female Chongzuo population,respectively.In contrast,A270 P and A270 V mutations of GABAR,the targets of phenylpyrazole insecticides,were found to be widely distributed in all tested populations,but with low frequency(0.10% ～ 0.64%).The G169 C and A251 G mutations of ACh E1,the target of organophosphorus insecticides,were found in all populations,and the mutation frequency was less than 0.60%.The above research results can provide theoretical basis for in-depth study of insecticide resistance mechanism of D.Citri,and facilitate the timely understanding of resistance status of the pest in field prevention and control of D.Citri,predict resistance risk in advance,and make corresponding adjustment of control measures.It is of great significance to ensure the healthy development of citrus industry and help the rural revitalization.