Study On The Distribution And Efficacy Of Azadirachtin Granules In Cabbage,Corn And Cotton

Azadirachtin,one of the most promising natural biopesticide,was sensitive to ultraviolet light and temperature.In our country,the preparations of azadirachtin provided to farmers were only for spray,such as emulsifiable concentrate,micro emulsionsand water dispersible granule.In this study,the cinnamon leaves and silica sand were use as granule carriers to prepara azadirachtin granules.The activity of azadirachtin granules against Spodoptera litura,Ostrinia furnacalis and Aphis gossypii was evaluated by soil application.The distribution of azadirachtin in there crops was analysised by high performance liquid chromatography.Results in this study could make a reference for the used pesticide soil application to control pests and diseases on the crops,and also for the distribution of pesticide.After atreatment with azadirachtin granules,the member of pest on three crops was reduced significantly.The efficacy wre increase first and then decrease with time goes on.In cabbage,the larvae of Spodoptera litura had obvious non-selective antifeedant activity and reached the highest of 46.64% and 58.72% at 7 days after application with two azadirachtin granules(135 g a.i/ha).The cabbage treated with azadirachtin granules(270 g a.i/ha)could cause the larvae death obviously and even reached 53.33% and 80.00% at 12 days after application.In corn,azadirachtin granules could reduce the harm of Ostrinia furnacalis.The control effect reached the highest in the 10 d after soil application,such as the test area of cinnamon leaf vector,its correct control effect reached 47.34% at 10 days after application.In cotton,soil application with azadirachtin granules could significantly inhibit the growth of Aphis gossypii and reduce their harm to cotton.The control effect reached the highest level of 53.34% and 86.50% at 7 days after application.The ruselts shown the efficacy of soil applicationwith azadirachtin granule was a slow process.In addition,the efficacy azadirachtin granules in cinnamon leaf carrier were higher than silica sand carrier,both on the activity against Spodoptera litura,Ostrinia furnacalis and Aphis gossypii.In the condition of water spray,azadirachtin in azadirachtin particles could be dispersed into the soil,and its dispersion behavioris regular.The mainly azadirachtin was concentrated in the soil depth of 0-20 cm,while the soil depth of more than 20 cm has only a few amount of distribution.Result shown the highest contents of azadirachtin in the soil depth of 0-10 cm,11-20 cm and 21-30 cm were 1.699 mg/kg,0.473 mg/kg and 0.134 mg/kg.What is more,the lateral dispersion of azadirachtin in the soil was significantly lower than that in the longitudinal direction.After the mixture of cinnamon leaf,the degradation behavior of azadirachtin in the soil was significantly inhibited and its stability was improved.The results shown the half-life of azadirachtin granules of silica sand and cinnamon leaf vector were 1.93 d and 3.64 d.In three crops,the contents and digestion dynamics of azadirachtin were very different in different plant parts.The half-life of azadirachtin in the soil growed crops was lower than in the blank soil.In the cabbage test area,the order of highest content of azadirachtin from high to low was stem,root and leaf.The half-life of azadirachtin in different parts of cabbage after after application with azadirachtin granules of silica sand and cinnamon leaf vector was 2.31 d to 3.15 d and 3.47 d to 4.95 d,respectively.The highest content and half-life of azadirachtin in inner leaves of cabbage were higher than those in outer leaves.In the corntest area,the highest content of azadirachtin was in the tassel,and the lowest was in the leaf.The half-life of azadirachtin in different parts of corn after after application with azadirachtin granules of silica sand and cinnamon leaf vector was 1.65 d to 3.01 d and 2.48 d to 4.62 d,respectively.In addition,content and digestion speed of azadirachtin in the different space of corn stem or leave were significant differences.In cotton test area,the highest content of azadirachtin in roots and stems was significantly higher than that in branches and leaves.The half-life of azadirachtin in different parts of cotton after after application with azadirachtin granules of silica sand and cinnamon leaf vector was 2.10 d to 3.01 d and 3.13 d to 4.33 d,respectively.The azadirachtin has different accumulation and digestion behavior in the leaves of cotton at different locations.Results in the three cropsexperiment area also shown compared with silica sand,cinnamon leaves increase the absorption of azadirachtin and extend the duration of azadirachtin.Results in this study indicate that the soil application with azadirachtin granules can be used for pest control on the crops.Azadirachtin mixed with cinnamon leaves could improve the efficacy significantly.Azadirachtin in the azadirachtin granules could be dispersed into the soil and absorbed by crops such as cabbage,corn and cotton.After absorbed by crops,the accumulation and digestion of azadirachtin in different parts of crops were very different.Different carriers have a significant effect on the distribution and digestion of azadirachtin.