Effects Of Imidacloprid On The Biological Characteristics Of Metopolophium Dirhodum(Walker)

Imidacloprid,a neonicotinoid insecticide,has a very good control effect on wheat aphids,which is a research hotspots in the field of the novel pesticides for control wheat aphids.This study was conducted to identify the impact of imidacloprid on the dynamic of Metopolophium dirhodum(Walker)in the mixed population of wheat aphids and its individual life paramaters and evaluate the level of imidacloprid resistance in M.dirhodum in order to provide the technical support for the application of neonicotinoid insecticides for control wheat aphids and provide the scientific basis for the comprehensive and control of wheat aphids and the integrated insecticide resistance management.The main results are as follows:1.Effects of imidacloprid seed coating on the dynamic of M.dirhodum in the mixed population of wheat aphidsImidacloprid seed coating were effective in reducing densities of S.avenae and R.padi for the whole wheat season,but the enhancement were somehow found on M.dirhodum.Imidacloprid seed coating affected the population structure of wheat aphids in Langfang,Hebei,and made M.dirhodum a dominant population.The bioassay showed that M.dirhodum was the lowest sensitivity to imidacloprid,but there was no significant difference between four wheat aphid species.However,the laboratory simulation showed that imidacloprid seed coating could significantly reduce the survival rate and fecundity of R.padi,S.avenae and S.graminum,but it was basically ineffective for M.dirhodum.Therefore,it is proposed that a comprehensive evaluation should be conducted in combined with indoor and field evaluation in pest resistance evaluation.2.Effects of imidacloprid seed coating on the laboratory population of M.dirhodumThe age-stage,two-sex life table of M.dirhodum was simulated under the imidacloprid seed coating.It was found that 66% of M.dirhodum's newborn nymphs could complete the entire life cycle under the above process,but the growth and development rate slowed down,the mean longevity was shortened significantly,fecundity decreased significantly and the life table parameters were altered: intrinsic rate of increase(r),finite rate of increase(?)and net reproductive rate(R0)decreased significantly,mean generation time(T)was significantly prolonged.Consequently,the population size of M.dirhodum on wheat plant treated by imidacloprid seed coating was significantly lower the CK after 60 d in the population prediction,but still reached approximately 30,000.Imidacloprid seed coating had a certain inhibitory effect on the M.dirhodum's population development.3.Effects of three sublethal concentrations imidacloprid on the life parameters of M.dirhodumThe three sublethal concentrations of imidacloprid(LC15,LC24 and LC35)were used to treat M.dirhodum,results showed: both the shortening of adult longevity and decline of fecundity of the F0 generation,which were negatively correlated with concentration,both LC24 and LC35 treatments were significantly different from CK.The F1 generation's population development was promoted as follows: the F1 generation's nymph stage was shortened,LC24 treatment was significantly different from CK;their mean longevity was extended,LC15 treatment was significantly different from CK;their fecundity increased,LC24 treatment was significantly different from CK;the life table parameters were altered: intrinsic rate of increase(r)and finite rate of increase(?)increased and mean generation time(T)was shortened,both LC24 and LC35 treatments were significantly different from CK,the increase on net reproductive rate(R0)was only significant difference between LC24 treatment and CK.The populations number of F1 generation of three treatments were respectively up to approximately 4.72 million(LC15),7.81 million(LC24),and 7.8 million(LC35)after 60 d After 60 d in population prediction,which was 2~3 times that of CK(2.47 million).The sublethal concentration of imidacloprid inhibited the contemporary population development of M.dirhodum,but promoted the development of the offspring population to some extent.4.Evaluation of imidacloprid resistance in M.dirhodumBioassary showed that among the eight tested insecticides,abamectin was found to be the most toxic to M.dirhodum,with the LC50 value of 32.06 mg/L,followed by matrine(34.32 mg/L),lambda cyhalothrin(40.71 mg/L),Chlorpyrifos Standard(98.11 mg/L),beta cypermethrin(112.18 mg/L),acetamiprid(388.17 mg/L),imidacloprid(470.16 mg/L)and thiamethoxam(561.35 mg/L).M.dirhodum was less sensitive to neonicotinoid insecticides acetamiprid,imidacloprid and thiamethoxam.The sensitivity of 9 geographic populations(BJYQ,HBCZ,HBDX,HBDZ,HBHD,HBXT,HBLC,HBLF and SDDZ)to imidacloprid in the northern wheat region of china were tested,it was found that M.dirhodum in different regions were all sensitive to imidacloprid and there was no significant difference.