The Study On Toxicity Determination And Mechanism To Plutella Xylostella By Aconite Alkaloids In Laboratory

Three different types of cruciferous vegetable crops was chosen as host to feeding the diamondback month,including Cabbage type rape, Gai Lan type rape and Chinese Cabbage. The results show that Brassica napus is significant differences compared to the other hosts,and it has the longest life cycle. Thus we choosed the Brassica napus as the final host. In the test of refrigerator test, the best days of refrigerator days is 10 for the eggs and pupae of diamondback, their hatching rate and egg rate will be affected if it is more than 10 days.By extracted the aconite alkaloids, the diester and single ester type of alkaloids are determined the final agent. Then antifeedant activity,stomach poison activity, growth inhibition activity and oviposition repellent activity are measured, and the regression analysis of the four kinds of activity are made.In the antifeedant activity, the highest non-selective antifeedant rate are 76.08% and 52.91%, non selective regression equation are y=-1.312+2.014 x and y=-1.666+1.716 x before detoxification and after.the highest selective antifeedant rate are 59.08% and 36.51%, selective regression equation are y=-0.859+1.141 x and y=-1.718+1.431 x. In the stomach poison activity, the fatality rate are 63.33% and 50%, the regression equation are y =-1.296+1.838 x and y=-1.386+1.379 x. In the growth inhibitory activity, the highest growth inhibition rate are 67.6%and 52.22%. The regression equation in turn are y=-1.283+1.73 x and y=-1.24+1.316 x.In the oviposition repellent activity, the highest non-selective oviposition repellent rate respectively are 73.96% and 74.36%, and the regression equation are y=-0.921+1.638 x, y=-1.040+1.725x; selective the highest oviposition repellent rate respectively are 83.93% and66.52%.The regression equation are y=-0.686+2.001 x,y=-0.902+1.639 x.It is seen from the above results, above the all insecticidal activity,oviposition repellent activity is the highest, antifeeding and growthinhibition activity are followed, stomach poison activity is the weakest.By comparing the effect on diamondback moth by single ester alkaloids and diester, the insecticidal activity decreased in different degree by hydrolysis, but it still is available in oviposition repellent activity and selectivity antifeedant activity.On the basis of the determination of toxicity, the appropriate concentration isbeenselected as the potted efficacy trials, Bt as a positive contract, distilled water as the blank contract. The results show that chemical control effect increase rapidly in the application of the5 th day, the highest decline rate of diamondback reaches 60.35% before hydrolysis, then it stays a stationary phase. It is showed that aconite alkaloids has protective effect on diamondback moth, and the efficacy has a sustained period. The sustained period remains about 3 to 5 days.The after hydrolysis of aconite alkaloids, the highest decline rate of diamondback moth reaches 55.37%, although it is weakened, but its medicinal effect can be further explored.