| Tenvermectins A and B are a kind of new avermectins,isolated from the fermentation broth of genetically engineered strain Streptomyces avermitilis MHJ1011.Compared with avermectins,ivermectins and milbemycins,tenvermectins were proved to possess better insecticidal property in the control of aphid,mite and other insect pests in agriculture and livestock parasite in animal husbandry.Due to the characteristics of broad spectrum,high efficiency and low toxicity,tenvermectins were considered to be a promising new generation of pesticides and veterinary drugs.The research contents of this thesis include three aspects:?a?Bioactivity of tenvermectin to Chilo suppressalis;?b?Research of tenvermectin photogradation andinfluencing factors in water environment;?c?the acute toxicity of tenvermectins on aquatic organism.1.Bioactivitiy of tenvermectin to Chilo suppressalis.The toxicities LC500 of tenvermectin A,tenvermectin B and avermectin B1a were 1.099?0.749?0.605mg/L.The three drugs has high bioactivity and avermectin B1a and tenvermectin B was higher than that of tenvermectin A.The results of field efficacy test that 2%of tenvermectin EC was 1.0,1.5 and 2.0 g/667 m2 treatment were 54.37%,61.60%and 68.11%and the three drugs had good control effect on Chilo suppressalis,2%tenvermectin EC and 2%avermectin EC were better than 2%milbemycins EC.2.Effect of light intensity,initial conventration,pH and temperature on the photodegradation of tenvermectin were studied.indoor simulated sunlight conditions,when the light intensity,initial concentration,p H,temperature changes,the half-life of the agent changes.With the light intensity of 6 500lx,11 500lx and 15 500 lx,the half-lives of tenvermectin A and B were 13.2,7.47,4.09h and 14.4,5.41,3.14h,the half-lives of avermectin B1a was 12.2,5.64 and 2.17h;While the initial concentration was 100,200 and 400mg/L,the half-lives of tenvermectin A and B were 5.17,7.49,9.05h and 3.48,5.41,7.85h,the half-lives of avermectin B1a was 2.59,5.64 and 9.23h;While the p H was 5,7 and 9,the half-lives of tenvermectin A and B were 6.54,7.63,6.78h and 4.92,5.41,4.88h,the half-lives of avermectin B1a was 4.58,5.64 and 5.09h;With the temperature of15?,25?and 35?,he half-lives of tenvermectin A and B were 8.93,7.62,4.13h and 10.5,5.47,3.88h,the half-lives of avermectin B1a was 9.78,5.64 and 4.11h.3.The standard experiment animals Brachydanio rerio,Scenzdesmus obliquus and Daphnia mgana stuas were used to study the acute toxicity of tenvermectins on aquatic organism.The96h-LC50oftenvermectinA,tenvermectinB,avermectinB1a,avermectin B1b,milbemycins,doramectin and slamection for Brachydanio rerio were 1.11,0.135,0.033 6,0.098 7,0.026 4,0.039 6 and 0.102 mg/L;The 72h-EC500 of tenvermectin A,tenvermectin B,avermectin B1a,avermectin B1b,milbemycins,doramectin and slamection for Scenzdesmus obliquus were 51.6,10.9,11.3,15.5,11.9,67.2 and 89.4 mg/L;The 48h-LC500 of tenvermectin A,tenvermectin B,avermectin B1a,avermectin B1b,milbemycins,doramectin and slamection for Daphnia mgana stuas were 1.17×10-3,0.363×10-3,0.219×10-3,0.344×10-3,22.1×10-3,0.237×10-33 and 0.0342×10-33 mg/L.Tenvermectins reduces the toxicity to aquatic organisms without reducing the bioactivity,therefore,it is better to use tenvermectin instead of avermectin,and tenvermectins have better development potential and value of promotion in the actual production. |
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