Effects Of Sublethal Concentrations Of Three Pesticides On Sitobion Miscanthi

Sitobion miscanthi?Takahashi?is a dominant population that harms wheat crops in China.In order to evaluate the effects of sublethal concentrations of abamectin·imidacloprid and beta-cypermethrin·imidacloprid and sulfoxaflor on the population density of Sitobion miscanthi,life-table analyses on the growth,development and population density of S.miscanthi F₀ and F₁generations were determined.and the important protective enzymes,target enzymes and detoxifying enzymes were determined at the same time,providing a theoretical basis for the reasonable control of S.miscanthi on production,The main results are as follows:1.Determination of toxicity and sublethal doses of three insecticides on Sitobion miscanthi.The results showed that,S.miscanthi LC₅₀ is ranked from high to low.Imidacloprid has imidacloprid 20%AS>clothianidin 20%SC>thiamethoxam30%SC>sulfoxaflor 22%SC>beta cypermethrin·thiamethoxam 9%SC>abamectin 3.2%EC>beta-cypermethrin 5%ME>beta-cypermethrin·imidacloprid 33%SC>abamectin·imidacloprid 3.15%EC?Imidacloprid has the weakest contact toxicity,with an LC₅₀ of up to 22.3493 mg/L,and the strongest contact toxicity of beta-cypermethrin,beta-cypermethrin·imidacloprid and abamectin·imidacloprid.The LC₅₀ of the abamectin·imidacloprid mixture and beta-cypermethrin·imidacloprid mixture were lower than the single abamectin,beta-cypermethrin and imidacloprid,indicating that the mixture had stronger toxicity than their single components.Based on the results of the virulence measurement,the abamectin·imidacloprid mixture and beta-cypermethrin·imidacloprid mixture were selected,sulfoxaflor also slected to exploring the sublethal effect,which can effectively control juice-absorbing pests that are resistant to neonicotinoid,synthetic pyrethroids,organophosphorus and Carbamate pesticides.The LC₁₀,of bamectin·imidacloprid and beta-cypermethrin·imidacloprid and sulfoxaflor were 0.0803,0.0988,1.2568 mg/L;LC₂₀ 0.1380,0.2055,2.1772 mg/L;LC₃₀ 0.2039,0.3484,3.2355 mg/L?2.Effect of sublethal doses of three insecticides on the fecundity and longevity of Sitobion miscanthi.The results showed that,the fecundity and adult longevity of S.miscanthi F₀ generation were significantly?P<0.05?lower compared to the control.Relatively,the lowest longevity and fecundity?5.32d,0.84 heads?occurred on the sulfoxaflor(LC₃₀)treatments.The abamectin·imidacloprid(LC₁₀,LC₂₀,LC₃₀),beta-cypermethrin·imidacloprid(LC₁₀,LC₂₀,LC₃₀)and sulfoxaflor(LC₁₀,LC₂₀,LC₃₀)shortened the adult longevity of F₁ generation by 4.85 d?7.76d,8.47 d,6.02 d?7.41 d,9.28 d,6.49 d,7.54 d,10.40 d.The fecundity was also reduced by35.85%,45.56%,55.47%,40.04%?49.48%,59.52%,44.80%?52.89%,60.71%.And nymphs prolonged 0.43 d,0.61 d,0.69 d,0.40 d,0.52 d,0.82 d.0.72 d,0.98 d,1.27 d,which were significantly?P<0.05?lower compared with the control.The higher the concentration of the pesticides,the shorter the adult longevity,and the lower the fecundity,and the effect of sulfoxaflor to inhibit the population density of S.miscanthi.Moreover,the sublethal concentration effect of each treatment increased the developmental duration,population doubling time?D_t?,innate rate of increase?r_m?,average generation time?T?,net reproductive rate?R₀?,and the finite rate of increase of the F₁ generation.However,the gross reproduction rate?GRR?was reduced.This indicates that,the sublethal concentrations of abamectin·imidacloprid,beta-cypermethrin·imidacloprid and sulfoxaflor could significantly inhibit the population density of S.miscanthi.3.Effect of sublethal doses of three insecticides on the important protective enzymes,target enzymes and detoxifying enzymes of S.miscanthi.The results showed that AchE activity was reduced in each treatment.Each treatment of abamectin·imidacloprid and beta-cypermethrin·imidacloprid SOD,POD,CAT,CarE,GSTs activity were enhanced.The sulfoxaflor sublethal concentration of S.miscanthi shows that,the enzyme activity of SOD increased significantly under the LC₁₀ and LC₂₀ treatment conditions?P<0.05?;POD increased significantly compared with the control?P<0.05?;the enzyme activity of CAT increased significantly in LC₂₀ and LC₃₀ treatment increased?P<0.05?;CarE activity increased;GSTs was not significantly different compared with the control?P>0.05?.