The Control Effect And Influencing Factors Of Lambda-cyhalothrin On Pieris Rapae And Myzus Persicae

Pieris rapae and Myzus persicae are important pests of cruciferous vegetables,which are widely distributed and cause serious damage.They pose a serious threat to vegetable production that will lead to tremendous economic loss.At present,chemical control is still the most effective way for controlling P.rapae and M.persicae,but excessive use of insecticides will cause problems such as resistance of insect pest to insecticides.This dissertation chooses the chemical insecticide Lambda-cyhalothrin,which is commonly used in production,as a test agent,and uses the common pests P.rapae and M.persicae in open field vegetables as test insects to conduct experiments for indoor virulence testing and pot efficacy.These experiments are conducted to clarify the control effect of Lambda-cyhalothrin on P.rapae and M.persicae and its influencing factors,and provide guidance for reducing the use of pesticides.The main findings of this dissertation are summarized as follows:?1?The use of Lambda-cyhalothrin as the original drug for P.rapae and M.persicae was determined using different bioassay methods.The experimental results demonstrated that the LD₅₀ of Lactobacillus chrysanthemi to the 3rd instar caterpillar was 4.353 ug·g^-11 for 48h,and the LC₅₀ measured by leaf-leaching feeding method was9.483 mg·L-1.The contact activity was higher than the stomach poisoning activity.It also showed that the LC₅₀0 of 48h determined by the leaf tube film method,spray method and immersion method for the young nymph of M.persicae were 10.000mg·L^-1 up and down.?2?Three different dosage forms of Lambda-cyhalothrin emulsifiable concentrate,Microemulsion,and Water Emulsion were diluted to different multiples to test the virulence on P.rapae and M.persicae by using the dip method.The results showed that2.5%of Lambda-cyhalothrin had the best control effect on third instar larvae of P.rapae and M.persicae,followed by Microemulsions.?3?The control effect of lambda-cyhalothrin on the young nymph of M.persicae was determined by exploiting spray method under the settings of three temperature and two kinds of vegetables.The results showed that under the same conditions,the control effect at 30°C was lower than performance at 26°C and 22°C,and the controll effect of Lambda-cyhalothrin against M.persicae on the pakchoi was better than that of cabbage.?4?The pot efficacy test of M.persicae with three different dosage forms of Emulsifiable Concentrate,Microemulsion and Water Emulsion was conducted.The results showed that the pot efficacy results were consistent with that of the indoor virulence test,indicating that the control effect of Emulsifiable Concentrate and Microemulsion on M.persicae was significantly better than that of Water Emulsion.?5?The spraying interval was set to 7 days,and the application times were set to 1,2,and 3 times respectively.The potted cabbage way sprayed with 2.5%Lambda-cyhalothrin EC.The results demonstrated that there was no significant difference in control effect between 2 and 3 treatments,but it was significantly higher than that of 1 application times.This dissertation studied the relationship between the dosage of Lambda-cyhalothrin and its control effect,as well as the factors which influence the control efficacy.It clarified the control effect of Lambda-cyhalothrin on P.rapae and M.persicae on vegetables and its influencing factors.The experimental bases for setting application standards of Lambda-cyhalothrin in the cultivation system of open-field vegetables were provided.