Resistance Monitoring And Insecticide-mixture For Nilaparvata Lugens(St?l)

Nilaparvata lugens(Stal),the brown planthopper(BPH)as a monophagous pest of rice seriously threats rice production of China and other Asian countries.Chemical control still remains the most practical way to suppress N.lugens populations,but frequent and wide use of synthetic insecticides controlling N.lugens had led to the development of in-secticide resistance.As a result,it is very necessary to know the resistance levels among different geographical populations to commonly used insecticides and to guide the rational use of insecticides in the field and resistance management.This study was aimed at knowing resistance levels of brown planthoppers to different insecticides by monitoring resistance among different geographical populations,and as-sessing the resistance risk of sulfoxaflor with resistance selection in laboratory;At the same time,in order to get efficient mixed insecticides for providing a strategy to delay resistance development of BPH,we conducted the research on co-toxicity of sulfoxaflor with the conventional insecticides.1.The resistance monitoring to commonly used insecticides in brown planthopperIn order to make the current resistance staues of brown planthoppers to insecticides commonly useded to control the brown planthoppers clear,In order to make current re-sistance statues of brown planthoppers to insecticides commonly used to control the brown planthoppers clear,this study used the rice stem dipping method to monitor the resicstance of field brown planthoppers collected from seven provinces and Shanghai city to ten insec-ticides in 2014 and 2015.The monitoring results are as followed.Of the 23 field populations of BPH collected in 2014 and 2015 in China,21 field populations were at medium to high resistance level to pymetrozine(47.0-fold to 339.9-fold).The resistance level of field populations in 2015 had a declined slightly compared with that of 2013 on the trend;The monitoring results of field BPH populations to thiamethoxam as a new neonicotinoid insecticide showed that the pop-ulations in 2014 all were at medium resistance level(28.1-91.0 fold),91.7%of all popula-tions in 2015 had developed high resistance level(206.1-773.9 fold),and the resistance had a significant rise from 2014 to 2015.In the monitoring of field BPH populations to niten-pyram,except that SH15(Shanghai)population had developed medium resistance lev-el(12.4 fold),the other 24 populations still were at low resistance level or under that,and the resistance had a rose slightly from 2014 to 2015.The monitoring results of field BPH populations to dinotefuran showed that the populations in 2014 were at low resistance level or under that(0.7-8.3 fold),93.3%of all populations in 2015 had developed medium re-sistance level(11,2-48.1 fold),and the resistance had increased significantly from 2014 to 2015.The monitoring results of field BPH populations to sulfoxaflor as a novel insecticide showed that the populations in 2014 were at low resistance level or under that(0.5-5.9 fold),92.3%of all populations in 2015 had developed medium resistance level(11.2-25.9 fold),and the resistance had increased significantly from 2014 to 2015.The monitoring results of field BPH populations to chlorpyrifos as organophosphorus insecticide showed that the dif-ferences of resistance ration were large(0.7-34.9 fold),the populations in 2015 were still at medium resistance level(11.2-25.9 fold)except that HX15(Hexian)population had devel-oped high resistance(114.8 fold),and the resistance level had continued to rise from 2014 to 2015.In the monitoring of field BPH populations to butene-fipronil,the populations in 2015 all were at medium resistance level(12.7-83.7 fold),and the resistance of partial areas populations had increased significantly compared with that of 2014.The monitoring results of field BPH populations to buprofezin showed that of the 22 field populations of BPH col-lected in 2014 and 2015 in China,21 field populations were at high resistance lev-el(167.0-fold to 1487.8-fold)except JH14(Jinhua)population still at medium remained re-sistance level(83.8-fold).The resistance level of field populations in 2015 had continued to rise compared with that of 2013 on the trend.All field BPH populations collected in 2014 and 2015 to imidacloprid were still at high resistance level(132.3-8477.7 fold),the re-sistance kept in up from 2014 to 2015.In the monitoring of field BPH populations to ethiprole,the populations in 2015 all were at medium or high resistance level(53.6-191.8 fold).In a word,the resistance problem of BPH to insecticides is still serious.So we sug-gest to forbid using imidacloprid,buprofezin and thiamethoxam to control the brown planthopper,and use pymetrozine,nitenpyram,dinotefuran,sulfoxaflor and chlorpyrifos as rotation inseticides to control the brown planthopper.2.The assessment of resistance risk in N.lugens to sulfoxaflorTo evaluate the resistance risk of N.lugens to sulfoxaflor and to provide positive guidance for scientific application of sulfoxaflor,N.lugens were selected in the laboratory for resistance to sulfoxaflor.The realized resistance heritability and generations holding a 10-time increase in LC50 were evaluated based on the Tabashnik's method(threshold trait analysis).The realized resistance heritability(h2)was 0.1069 for F0-F13 and 0.2386 for F13-F20,during which there were a total of 1 generations without selection.The realized re-sistance heritability for the entire selection period was 0.1430,according to which it would take 30.5-13.8 generations for N.lugens to develop 10-time resistance to sulfoxaflor under selection pressure of 50%-90%mortality for each generation.These results indicated that N.lugens may have resistance risk to sulfoxaflor.3.The co-toxicity of sulfoxaflor mixed with five insecticides for controlling N.lugensTo study the co-toxicity of sulfoxaflor mixed with five insecticides for controlling N.lugens and get the efficient mixture,we measured the LC50 of the 3rd instar nymph of BPH to sulfoxaflor mixed with pymetrozine,nitenpyram,dinotefuran,chlorpyrifos and ethiprole at different ratio using the rice stem dipping method.The results showed that sulfoxaflor with five insecticides in suitable mixing ratios had relatively high co-toxicity against the brown planthopper by co-toxicity coefficient method.Among them,the mixtures of sul-foxaflor with chlorpyrifos at ratio arrange from 1:5 to 1:7,pymetrozine at ratio arrange from 1:7 to 1:10,dinotefuran at ratio arrange from 3:1 to 2:1,nitenpyram at ratio arrange from 1:1 to 1:3 and ethiprole at ratio arrange from 1:7 to 1:10 have a significant additive effect.