Sublethal Effects Of Bate-cypermethrin On Carposina Sasakii Walsingham(Lepidoptera: Carposinidae)

In addition to direct mortality of target pests,as the insecticides degrade over time and individual differences in susceptibility to insecticides,some individuals are likely to be affected by sublethal doses of the insecticides in the agricultural ecosystem.Pyrethroids were one of the most extensively used for controlling pests?Lepidoptera?in the field.However,the rapid development of resistance to pyrethroids in many pests?L.?led a significant and increasing threat to their effective use or sublethal effects of pesticide residues in the field.In this study,we just initiated using a major fruit-boring pest in north China,Carposina sasakii Walsingham?Lepidoptera:Carposinidae?,as a model organism to evaluate the sublethal effects of beta-cypermethrin on the fruit-boring pests,and revealing the sublethal effects of the beta-cypermethrin on the biological characters of experimental populations,sex pheromone communication system and detoxifying enzyme activities of C.sasakii.We hope the results would help to provide a theoretical basis and method reference for the researches of integrated fruit-boring pest control and its resistance management.The results are as follows:1.Sublethal effects of bate-cypermethrin on the biological character of C.sasakii and the life table for its experimental populations were builtSublethal concentrations of bate-cypermethrin reduced the survivorship and the ratio of female moths of F₀ and F₁ generations.The values of boring rate,dropping rate,survival rate of larval,emergence rate and sex ratio??/??reduced with the increase of the insecticide concentration.After the newly hatched larvae of F₀ generation were exposed to the sublethal concentrations(LC₁₀,LC₂₀ and LC₄₀)of bate-cypermethrin,the average numbers of eggs laid per female per day were 34.09,33.00 and30.12 respectively,correspondingly the numbers of eggs laid per female were 284.90,276.56 and252.89 respectively,both were significantly less than that of the control?38.02 and 320.98,respectively?.When the newly hatched larvae of F₁ generation were exposed,the average numbers of eggs laid per female a day were 34.57,30.82 and 33.39,respectively,which were significantly higher than that of the control?27.97?.Meanwhile,the numbers of eggs laid per female after treatment with bate-cypermethrin at LC₂₀ and LC₄₀ were 304.45 and 298.31,respectively,which were significantly higher than that of the control?271.40?.However,there was no significantly difference in the developmental duration of each stage and weights of larvae.Life table analysis showed that the net reproductive rate?R₀?decreased significantly in a dose-dependent manner after the treatment.Moreover,the treatments obviously reduced the relative fitness value?R_f?of C.sasakii in F₀ and F₁ generations,but its reproductive disadvantage would be improved in C.sasakii of F₁ generation.2.Sublethal concentration of beta-cypermethrin influences fecundity and mating behavior of C.sasakii adultsAfter adults treated with the LC₁₀-bate-cypermethrin,calling rhythm or periodicity of calling of adult survived females was similar but calling rate was lower than control females.Meanwhile,the beta-cypermethrin-treated females started to call 0.5 h earlier.In the mating choice experiment,males in control or LC₁₀-beta-cypermethrin treatments preferred to mate with females in control.Furthermore,the mating rate,fertility?total number of eggs laid per female?and adult longevity of adults were remarkably decreased as compared with that in control when the adults were exposed to 10%lethal concentration(LC₁₀)beta-cypermethrin(LC₁₀?×LC₁₀?),and the age-specific survival rate?S_x?was also negatively affected by sublethal beta-cypermethrin especially for the LC₁₀?×LC₁₀?mating combination.However,the age-specific fecundity?f_x?was stimulated particularly in the combination of CK?×LC₁₀?.Interestingly,the oviposition period was prolonged and the number of eggs was significantly increased for combinations of CK?×LC₁₀?and LC₁₀?×CK?.3.Effects of sublethal concentration of bate-cypermethrin on activities of detoxifying enzymes in C.sasakii adultsAfter adults treated with the sublethal concentration of the bate-cypermethrin for 24 h,the activities of ECOD were inhibited significantly after the LC₁₀-bate-cypermethrin treatment.As the beta-cypermethrin concentration increases,the activities of ECOD were induced gradually especially for the LC₄₀-beta-cypermethrin treated adults whose ECOD activity was significantly higher than that of the beta-cypermethrin-free controls.Additionally,the activities of CarE and GSTs in male moths increased.The activities were inhibited in females after treated with LC₂₀ or LC₄₀ concentration of beta-cypermethrin.After beta-cypermethrin treatment,the activities of the detoxifying enzymes were increased at the beginning and then decreased.Moreover,the activities of three detoxifying enzymes in adults fluctuated more significantly with the increase of beta-cypermethrin concentrations and distinct sex differences may exist.According to the short-term physiological responses of the C.sasakii adults to beta-cypermethrin,the above mentioned three detoxifying enzymes in female or male moths play a comparatively active role for it and the activities of the detoxifying enzymes were increased at first and then decreased.Different physiological function of female and male moths,as well as the differences in susceptibility to insecticides,resulted in the dosage and sex differences of the C.sasakii adults responses to the sublethal concentrations of the beta-cypermethrin.