Acute Toxicity And Sublethal Effect Of Imidacloprid And Others Insecticides On Chrysoperla Sinica

Chrysoperla sinica is an important predatory natural enemy widely distributed in various regions of China.It has the advantages of strong predation ability,rapid reproduction,la rge number of occurrences,and artificial breeding.It can be used as an important natural enemy in biological control.At present,the spray method is the prevention and control of pests in China,which has a great negative impact on natural enemies including C.sinica.In order to understand the acute toxicity and sub-lethal effect of insecticides on C.sinica larvae,the eight insecticides such as imidacloprid were determined in this study.The safety of eight pesticides to C.sinica larvae ware evaluated,and the sublethal effects of some of the four insecticides on the C.sinica were determined.The main results are as follows.1.The toxicities of eight insecticides such as imidacloprid against the 2nd instar larvae of the lacewing were determined.By comparing the LC₅₀ and LC₂₅ values of different insecticides,it was found that chlorpyrifos had the highest toxicity to the larvae of the C.sinica,with an LC₅₀0 value of 1.16 mg/L.Lambda-cyhalothrin had the lowest toxicity to the larvae of C.sinica,with an LC₅₀ value of 175.45 mg/L.The toxicity sequence of the eight insecticides to the larvae of the C.sinica larvae as:chlorpyrifos>thiamethoxam>emamectin benzoate>indoxacarb>beta-cypermethrin>imidacloprid>dinotefuran>lambda-cyhalothrin.2.The relative safety coeffcients of 8 insecticides against C.sinica were calculated.The results showed that chlorpyrifos was a very high-risk insecticide for C.sinica;the relative safety factor of thiamethoxam was between high risk and high risk.beta-cypermethrin,imidacloprid,indoxacarb,emamectin benzoate,and dinotefuran are of medium risk range;The relative safety coefficient of lambda-cyhalothrin was the highest in the low-risk range.3.Under the lethal concentration of indoxacarb,the F₀ and F₁ generations pupal weight,the average number of eggs per female,the hatching rate of eggs,and the survival rate of larvae were significantly reduced.The F₀ generation larval duration and pupal period were significantly prolonged,and the survival rate of the F₀ generation lacewing larvae was significantly reduced.There was no significant effect on the emergence rate of C.sinica.Under the sublethal concentration of emamectin benzoate,the emergence rate and survival rate of F₀ and F₁ of C.sinica was significantly reduced.The survival rate of adult F₀was significantly reduced.The F₁ generation of the pupal period was prolonged.The F₀generation of the C.sinica adults increased the average number of eggs per female compared with the control group,but the hatching rate of the eggs was significantly reduced by only57.78±8.39%.The average number of eggs per egg and hatching rate of the F₁ generation decreased significantly.There is no effect on the on pupal weight and duration of C.sinica larvae.Under the sublethal concentration of imidacloprid,the F₀ and F₁ generations of pupal weight,the survival rate of adults,the average number of eggs per female,and the survival rate of larvae were significantly reduced.The F₀ and F₁ generations of pupal period were significantly prolonged.There was no significant effect on the emergence rate of the two generations of C.sinica,which significantly reduced the hatching rate of F₀ eggs.The larval duration of F₁ C.sinica larvae was significantly prolonged.Under the sublethal concentration of lambda-cyhalothrin LC₂₅,LC₅ and LC₁ the pupal weight,emergence rate and adult survival rate were significantly reduced.The survival rate of adult under lambda-cyhalothrin LC₂₅ was only 5.66%,and the pupal period was significant prolonged and more pronounced as the concentration increases.Under the sublethal concentration of lambda-cyhalothrin LC₁,the average number of eggs per female,egg hatching rate and larval survival rate of C.sinica were significantly reduced,which significantly prolonged the larval duration of C.sinica larvae.In conclusion,the sublethal concentrations of imidacloprid,indoxacarb,emamectin benzoate LC₂₅ and the three sublethal concentrations of lambda-cyhalothrin LC₂₅,LC₅ and LC₁ all have certain influence on the growth,fecundity and population number of lacewings,among which the high efficiency cypermethrin LC₂₅5 has the greatest influence.