Cryptics Species,the Ratio Of Vector-borne Diseases And Insecticide Resistance Of Bemisia Tabaci Populations In China

Bemisia tabaci,which consist of many cryptic species,is an invasive and destructive pest of many protected and field crops worldwide.Among all the B.tabaci cryptic species,the cryptic species MEAM1 and MED are two damaging crop pests.In addition,the invasion and spread of the Bemisia tabaci was accompanied by outbreaks of B.tabaci-transmitted viruses,which has brought a huge loss.At present,in China,chemical control still the main method to control B.tabaci in the field.But MED have been producing a high resistance to common pesticides.we monitor the composition of B.tabaci B and Q biotypes in the field populations.We also survey the frequency of viruses（e.g.TYLCV,ToCV and CCYV）in the field-collected B.tabaci B.Finally,we focus on the susceptibility of B.tabaci（egg,nymph,adult）to several insecticides in different action modes.The research results are as follows:1.We monitored the distribution dynamics of MEAM1 and MED cryptic species in China’s fields in 2017-2018.87 populations samples in all were collected in 2017,among which 70 populations were B.tabaci MED,5 were MEAM1 and 12 were mixture of B.tabaci MEAM1 and MED populations.128 populations samples in all were collected in2018,among which 111 populations were B.tabaci MED,5 were MEAM1 and 12 were mixture of MEAM1 and MED populations.MED is the dominant population（≥50%）with a ratio of 94%in 2018.Bemisa tabaci MED has been displacing MEAM1 in the field.2.We monitored the distribution dynamics of TYLCV,ToCV and CCYV in the population of B.tabaci in China in 2017-2018.Carrying rates of TYLCV was detected in 11populations across 9 provinces in 2017 and in 16 populations across 12 provinces in 2018.All the tomato populations were infected by TYLCV.In addition,the percentage of TYLCV–infected individuals were over 90%.TYLCV is further spreading in China.Among the 11 populations of Bemisia tabaci collected in 2017,the percentage of ToCV–infected（≥50%）populations was 9%.Among the 15 populations of Bemisia tabaci collected in 2018,the percentage of ToCV–infected（≥50%）populations was 47%.ToCV has further spread in China.In 2013,we collected 22 populations across 12 provinces of which the percentage of CCYV–infected（≥50%）populations was 27%.In 2018,we collected 31 populations across 16 provinces of which the percentage of CCYV–infected（≥50%）populations was35%.CCYV is slowly spreading to various provinces in China.After Bemisia tabaci infected have been identified,most of them are MED cryptic species.TYLCV,ToCV and CCYV are spreading in various regions of China with the spread of Bemisia tabaci.3.We monitor the resistance of B.tabaci in the field in 2017 and 2018.Adults from eight field strains,respectively,did not exhibit resistance to abamectin.All the LC₅₀ were<0.5 mg/liter.Cyantraniliprole and spirotetramat were effective to larvae,and All of the LC₅₀were<7 mg/liter in 2017 and<8 mg/liter in 2018,respectively.Cyantraniliprole was also effective to eggs.All the LC₅₀ were<12 mg/liter in 2017 and<20 mg/liter in 2018,respectively.In conclusion,the insecticides,abamectin for adult,cyantraniliprole and spirotetramat for larvae and egg selected still effective to B.tabaci in China in 2017(2017LC₅₀/2016 LC₅₀<3).In 2018,the resistance of Bemisia tabaci adults to avermectin developed rapidly in the Haidian,Beijing,and Yuncheng,Shanxi(2017 LC₅₀/2016 LC₅₀≥3).Thus,three insecticides use in rotation should control B.tabaci and slow down the generation of insecticide resistance in the long term.The results of this study provide a more comprehensive basis for the effective and sustainable control of B.tabaci in the field.