Camptothecin Insecticidal-Activity And Mechanism To Plutella Xylostella L.

Camptothecin is a kind of compound which belongs to quinoline,it mainly exists in Camptothecia acuminata Decaisne of Nyssaceae. In previous research, a large amount of experiment was done on camptothecin extraction, such as improve extracting method, insecticidal activity of camptothecin was tested etc. The results showed that camptothecin extraction had several different type of action: Nearly had no Contact Toxicity, had antifeedant activity,stomach activity and strong growth-inhibition effect against Plutella xylostella L. All different extraction presented strong oviposition deterent effect against the Plutella xylostella L. adults. The extraction of alcohol ultrasonic had displayed potentials of ovicidal action. This paper studied on mode of action and mechanism of camptothecin to Plutella xylostella L. by bioactivity method and PAGE,enzyme activity assay,HPLC technology etc. the results showed that:(1).Treated with camptothecin, ecdysis of larvae of Plutella xylostella L. was abnormal, tested insect body showed shrink symptom, and abnormal pupation appeared;(2).All concentration of camptothecin had a little toxicity effects to larvae of Plutella xylostella L. by contact method, 2mg/mL led to high lethal rate of 90%, so we could conclude that camptothecin had strong stomach poisonous, LC₅₀ is 762.5532mg/L(3).Camptothecin had significant inhibition effect to growth increase of Plutella xylostella L. After treated with camptothecin, the time of pupation was put off, the number of abnormal pupation increased. Eclosion rate decreased. The control group's normal pupation is 63.3%, but 2mg/mL group is only 6.67%; Treated with 500mg/L,the abnormal pupation abound to 30% at 8d, and the normal eclosion rate is only 30% of control group.(4).By PAGE method, In 24 hours, camptothecin had strong activation to esterase in Plutella xylostella L.(5).Camptothecin got the MH titres down significantly, induced synthesis of JHâ…¢, put off the normal pupation time, so disturbed normal growth and pupation of larvae of Plutella xylostella L.All in all, camptothecin had effect of growth inhibition, eclosion rate decreased against Plutella xylostella L. camptothecin's effect on change of JH titres and MH titres might be an important reason of those effect.