Effects Of Insecticide Stress On Population Competition Of Aphis Gossypii And Acyrthosiphon Gossypii

Aphis gossypii and Acyrthosiphon gossypii survived together in cotton,which caused huge losses to cotton.In this study,Aphis gossypii and Acyrthosiphon gossypii were conducted as the research objects,1)the occurrence quantities of Aphis gossypii and Acyrthosiphon gossypii under different chemical control conditions in different experimental sites were investigated regularly by using the "Z" type survey method.2)The sensitivities of Aphis gossypii and Acyrthosiphon gossypii to three insecticides were determined by leaf soaking bioassay and field efficacies comparison method.3)The sublethal concentration of imidacloprid were used to feed Aphis gossypii and Acyrthosiphon gossypii to analyze the effects of sublethal concentration on the growth of Aphis gossypii and Acyrthosiphon gossypii.4)The changes of populations and rm of Aphis gossypii and Acyrthosiphon gossypii with different concentrations of insecticides after 1 d,3 d and 7 d with different initial single populations and mixed populations of Aphis gossypii and Acyrthosiphon gossypii to indicate the effect of insecticide stress on population competition of Aphis gossypii and Acyrthosiphon gossypii.The main experimental results were as follows:1 Population quantities of Aphis gossypii and Acyrthosiphon gossypii under different chemical control conditions in different experimental sitesIn 2018 and 2019,the most number of times chemical control were Regiment 12 experimental site,with 6 and 9 times,respectively.The frequency of chemical control used in 2019 increased compared with that in 2018 in different experimental sites.In 2018 and 2019,the most frequently insecticides were imidacloprid and acetamiprid.In 2018,the highest peak populations of Aphis gossypii and Acyrthosiphon gossypii of Regiment 9,Rregiment 12,Awati,Tumxuk experimental sites were 14213.8 and 9123.2,21330.8 and 7113.5,16732.4 and 8831.1,14963.7 and 6375.8 heads/100 plants,respectively.In 2019,these values changed to 40031.7 and 38762.8,53742.7 and 560.2,16176.7 and 14330.2,53742 and 8212.5 heads/100 plants,respectively.In experimental sites without and with few insecticides,the populations of Acyrthosiphon gossypii were larger than Aphis gossypii in the early stage.While in the middle and late stages,Acyrthosiphon gossypii had less population.It was noticed that the peak populations of Aphis gossypii were always higher than that of Acyrthosiphon gossypii.2 Comparison of sensitivities of Aphis gossypii and Acyrthosiphon gossypii to three insecticidesThe LC50 of Aphis gossypii and Acyrthosiphon gossypii to imidacloprid in Alar,Awati,Tumxuk experimental sites were 45.52 and 17.44,21.41 and 8.73 L,25.60 and 12.63 mg/L,respectively.The LC50 to flutamide were 215.14 and 209.95,201.03 and 207.07,216.18 and 217.80 mg/L,respectively.The LC50 to pymetrozine were 367.43 and 369.30,362.58 and 357.12,373.98 and 369.55 mg/L,respectively.It was concluded that the sensitivities of Aphis gossypii to imidacloprid in every experimental site were all lower than that of Acyrthosiphon gossypii,and there were no significant differences in the sensitivities of pymetrozine and flutamide between Aphis gossypii and Acyrthosiphon gossypii.In the field experiment,the reduction rates of Acyrthosiphon gossypii population were significantly higher than thoso of Aphis gossypii after the application of imidacloprid in every experimental site.One day after applications of flutamide and pymetrozine,there were significant differences of reduction rates in every experimental site.However,there were no significant differences after 3 and 7 d.3 Effects of imidacloprid sublethal dose on the growth of Aphis gossypii and Acyrthosiphon gossypiiIn imidacloprid LC30 treatment,the average fecundity of F0 generation of Aphis gossypii and Acyrthosiphon gossypii reduced by 29.58%,14.31%and the average fecundity of F1 generation of Aphis gossypii and Acyrthosiphon gossypii reduced by 51.53%,20.13%,respectively.Besides,the results of population life table parameters demonstrated that finite rate of increase and the average development duration of F1 generation were deceased significantly in the treatments of imidacloprid in comparison with control.However,the intrinsic rates of increase(rm)of F1 generation of both aphid species were increased following the treatment of imidacloprid.The rm of Aphis gossypii and Acyrthosiphon gossypii were 0.368 and 0.279,respectively,which were significantly higher than the control treatments,and the rm of Aphis gossypii was 1.32 times as high as Acyrthosiphon gossypii.The doubling time of the two species of aphids were 1.882 and 1.806 d,respectively,which were significantly lower than that of the control treatments.4 Effects of three insecticides on population competition of and Acyrthosiphon gossypiiThe populations of Aphis gossypii and Acyrthosiphon gossypii with individual population and mixed population decreased abruptly after 1 d treatment,and the populations and rm of Aphis gossypii were larger than that of Acyrthosiphon gossypii after 7 d and 14 d treatment by imidacloprid.At concentrations of LC30 and LC50 of pymetrozine and flutamide,the populations of Aphis gossypii were larger than Acyrthosiphon gossypii in individual populations.For the mixed populations,the populations of Aphis gossypii were larger than Acyrthosiphon gossypii after 7 and 14 d with Aphis gossypii:Acyrthosiphon gossypii 15:15 and 20:10.The rm of Acyrthosiphon gossypii were larger than that of Aphis gossypii after 7 d treatment with LC50 at the ratio of 10:20.On the opposite,the rm of Acyrthosiphon gossypii were less than Aphis gossypii after 7 d treatment with single and mixed populations at other concentrations.These showed that Aphis gossypii had stronger competitive advantages than Acyrthosiphon gossypii under different initial insecticides and populations.