Sublethal Effects Of Nitenpyram On Two Cotton Aphids At Different Temperatures

Acyrthosiphon gossypii Mordviiko and Aphis gossypii Glover are two common types of aphids in Xinjiang cotton area.From the pre-bud stage to the middle and late stages,the population advantage of Ac.gossypii changed into the population advantage of Ap.gossypii.However,due to the influence of temperature,pesticides and other external environments in the process of transformation,recently Ap.gossypii has also transformed into dominant populations before the squaring stage.The results of this study,sublethal effects of nitenpyram to two cotton aphids at different temperatureson,will provide a theoretical basis for using insecticides reasonably in cotton fields,knowing changes of the interspecific relationship of two aphids.The results are as follows:1.The LC₅₀of nitenpyram to Ac.gossypii at 16℃,20℃,24℃ and 28℃ were 32.23 mg/L,15.44mg/L,7.82 mg/L and 2.69 mg/L,respectively.The LC₅₀of nitenpyram to Ap.gossypii adults were 81.90mg/L,61.10 mg/L,29.66 mg/L and 22.17 mg/L,respectively.The relative toxicity indexes of nitenpyram to Ap.gossypii and Ac.gossypii were 2.54,3.96,3.79 and 8.24 at four temperatures.The toxicity of nitenpyram to two aphids increased with the increase of temperature,and Ap.gossypii was more sensitive to nitenpyram than Ac.gossypii.2.At four different temperatures,including 16℃,20℃,24℃ and 28℃,the net reproductive rate（R₀）of nitenpyram LC₂₀to the parental generation（G0）of Ac.gossypii decreased by 9.11%,13.88%,28.13%and 52.45%,respectively.At 16℃,the intrinsic rate of increase（r_m）and finite rate of increase（λ）were observably lower than those of the control,and the population doubling time（DT）was prolonged.At 20℃,24℃ and 28℃,except for the differences in r_m,λand DT,the population parameters of mean generation time（T）and gross reproductive rate（GRR）were markedly higher than those of the control,and the GRR was significantly lower than that of the control.Moreover,with the increase of temperature,the difference is greater.After treatment with nitenpyram,the r_mandλof G1 generation of Ac.gossypii decreased significantly at 16℃ compared with the control.At 20℃,24℃ and 28℃,except for differences in r_mandλ,the population parameters of T,APOP and TPOP were significantly longer than those of the control,and the difference increased with a rise of temperature.At 16℃ and 20℃,the sublethal effect of G2 generation was weakened,but there was no significant difference compared with the control group.At 24℃ and 28℃,r_mwas significantly lower than that of the control.3.The G0 generation of Ap.gossypii was treated with 3.60 mg/L nitenpyram.At 16℃,the population parameters of R₀ and GRR of G0 generation were not significantly different from those of the control.The population parameters were significantly affected（increased or decreased）at 24℃ and 28℃.At four temperatures,the R₀ of the treatment group decreased by 2.38%,3.82%,10.37%and 18.87%,respectively.R₀,r_mandλall decreased,with the increase of temperature,the difference is gradually obvious.There was no significant effect on the parameters of G1 generation at 16℃,both r_mandλincreased significantly at20℃,R₀ increased significantly at 24℃,R₀,r_m,λ,TPOP and T had significant effects at 28℃.In G2generation,except that R₀ and APOP increased significantly compared with the control at 24℃,the parameters of other treatments were not significantly different from those of the control.4.At the same temperature,the survival rate l_xand reproduction rate m_xof Ac.gossypii G1 treated with nitenpyram decreased,showing an inhibitory effect（R₀ and r_mdecreased）,while the increase of l_xand m_xof Ap.gossypii G1 showed a stimulating effect（R₀ and r_mincreased）,as the temperature increases,the difference increases.