Effects of sublethal concentrations of imidacloprid on the transgenerational life table characteristics of Schizaphis graminum (Rondani)

【Objective】 The effects of the imidacloprid on the parental generation and two successive filial progeny of the Schizaphis graminum(Rondani)were assessed. It was beneficial for revealing the response of an experimental population of S. graminum to sublethal concentrations of imidacloprid through multiple generations,which could provide a theoretical basis for the reasonable usage of insecticides in the field.【Method】 The life table and survival characteristics of S.graminum in the parental generation(F₀)and two successive filial progeny(F₁ and F₂)were detected after the parental individuals have been exposed to different sublethal concentrations of imidacloprid(LC₂₀ and LC₄₀).【Result】 Different concentrations of imidacloprid exerted different influences on the survival rate and growth of S. graminum. The LC₂₀ concentration of imidacloprid had no significant effect on the survival rate and median survival time of the parental and successive two filial generations of S. graminum populations(P>0.05,the same below). However,the LC₄₀ concentration of imidacloprid in the F₀ generation significantly reduced the survival rate of aphids(P<0.05,the same below),and median survival time of the LC₄₀ group was only 71.55% compared with the control aphids. However,there was no significant effect on the median survival of the two offspring populations. The survival rate and longevity of the LC₄₀ group increased with numbers of generations in three successive generations. The LC₂₀ concentration of imidacloprid had no significant effect on the fecundity of the parental and successive two filial generations of S. graminum populations compared with control.Moreover,the LC₄₀ concentration of imidacloprid significantly reduced the fecundity of aphids in the F₀ generation,while without a significant effect on the fecundity of S. graminum populations in the F₁ and F₂ generations. In addition,within generations,the values of life table characteristics of S. graminum in the LC₂₀ or LC₄₀ group were no significantly different compared with those of the control of both two successive filial generations. Moreover,the values of life table characteristics of aphids to the same sublethal concentrations of imidacloprid(the LC₂₀ or LC₄₀ group)were not significantly different between their two successive filial progeny.【Conclusion】 The results suggests that the survival rates,life span,and fecundity of parental aphids are significantly different from groups(LC₂₀ and LC₄₀)exposed the two sublethal concentrations of imidacloprid with obvious dose effect,while this effect on life table characteristics of S. graminum in two treated groups is not significantly different in the two successive filial generations.