Study The Control Of Bamboo Insect Pests For Tenvermectin And Its Derivatives Insecticidal Structure-activity Relationship

There is now a greater variety of diseases and insect pests in the bamboos,which caused the increasingly serious harm,big economic loss and high ecological risk to bamboos.But there is no registered pesticide available for controlling diseases and insect pests in the bamboos.Tenvermectin,which have many advantages like characteristics of broad spectrum,high efficiency and low toxicity,is a kind of new 16-membered macrocyclic lactone antibiotics isolated from the fermentation broth of genetically engineered strain Streptomyces avermitilis MHJ1011.In the paper,tenvermectin was evaluated for its biological activities against four species of insect pests in the bamboos,namely,atrachea vulgaris,coclebotys coclesalis,adult mite of bamboo,bamboo wireworms.And field trials were carried out to study the efficacy,the distribution in bamboo trees and the degradation in soil with pesticide agent producing,which prepared in laboratory.In an effort to discover new molecules with good insecticidal activities,more than 72 new tenvermectin derivatives were synthesized,isolation from strain Streptomyces avermitilis MHJ1011 and evaluated for their biological activities against four species of arachnids and insects by structure-activity relationship between the derivatives and insecticidal activities.The dates of the paper can be useful registration the pesticide varieties for insect pests in the bamboos.（1）The biological activities of tenvermectin was evaluated against four species of insect pests in the bamboos,namely,atrachea vulgaris,coclebotys coclesalis,adult mite of bamboo,bamboo wireworms.The tested compound showed potent inhibitory activities against three insect species with the value of LC₅₀ 2.99、0.07、276.52、20.32 mg/L,which is priority selection for developing bamboo special pesticide.The 2%green EC formulations and their stability were developed and analyzed by high performance liquid chromatography（HPLC）.The solvents of turpentine oil and ethyl acetate can slow decomposition of tenvermectin efficiently.The 2%ME formulations was developed and Quality indicators was tested.The field trials were carried out to study the efficacy of coclebotys coclesalis,bamboo wireworms and adult mite of bamboo.The field efficacy were 85.79%,87.97%,91.78%after injection 2%green ME formulations 3 months against coclebotys coclesalis.The residue of 2%ME formulations can be transpiration entered into the stem translation tissue from 5 days after injection,and reached the maximum（0.45±0.03mg/kg）in the bamboo.The field efficacy was93.12%after spray 15 days by 20 mg/kg of 2%EC formulations.Field experiment were tested with 4%tenvermectin WG formulations against bamboo wireworm.The field efficacy was68.29%treated with the concentration of 40 kg/hm² 1 year later.So we can choice of control time according to the occurrence period of insect pests,because the degradation speed of tenvermectin was 10 days in the soil and there is no residue in the bamboo shoots.（2）In an effort to discover new molecules with good insecticidal activities,more than 96 new tenvermectin derivatives were synthesized and isolation from strain Streptomyces avermitilis MHJ1011 by similar synthesis,sub-structure connection principle and acid-catalyzed hydrolysis methods at C-4’’、C-4’、C-13、C-5 sites of compounds.The synthetic method of methylamino tenvermectin benzoate（salt）,acetylamino tenvermectin and lepimectin were studied.All compounds were identificated by LC-MS and HMR（H、C）.Their biological activities were evaluated against four species of arachnids and insects in the bamboos,namely,atrachea vulgaris,coclebotys coclesalis,adult mite of bamboo and bamboo wireworms.All the tested compounds showed potent inhibitory activities against four insect species.Notably,the majority of compounds exhibited high selectivity against coclebotys coclesalis and bamboo wireworms,some of which were much better in comparison with tenvermectin.Especially compound methylamino tenvermectin benzoate（salt）(LC₅₀:19.52mg/L and 265.47mg/L)were better more active than tenvermectin(LC₅₀:20.11 and 273.49 mM),respectively.And tenvermectin B(LC₅₀:2.99 mg/L and 0.07 mg/L)was better more active than other compounds against atrachea vulgaris and adult mite of bamboo,respectively.（3）The compounds relationship between structure and insecticidal activity was elucidated.It was realized that the hydroxy at the 5-position and both oleandrose at the13-position were essential for high potency and broad-spectrum.Tenvermectin was 2-3.5-and 3.5-8-fold more active than 4’-epi-Amonosaccharide and 13-aglycon substituents compounds.Subsequently,a number of lipophilic 13-substituents which mimicked the bisoleandrosyloxy of the compounds were also found to restore activity.But Polar substituents at the 13-position such as the hydroxy and amino groups showed diminished activity.The 4"-position has been the most frequently studied because of its easy access.Acyl,amino,or thio substitutions at this site have changed solubility,distribution,stability,and diversity of spectrum,while maintaining the overall potency of the parent molecule.It was realized that the hydroxy at the 5-position was essential for high potency and broad-spectrum.Tenvermectin was same active as 5-Oxo-substituents,and both more active than5-carboxide-substituents compounds.The alkyl chain and heterocycle-substituent group at the25-position is superior to other compounds.Polar substituents is showed diminished activity.The ideal molecular structure of tenvermectins maintained the hydroxy at the 5-position and both oleandrose at the13-position,and meanwhile alkyl chain and heterocycle-substituent group at the25-position,Acyl,amino,or thio substitutions at 4"-position have changed solubility,distribution,stability,and diversity of spectrum,while maintaining the overall potency of the parent molecule.In the paper,the 2%green EC used for foliar spray application and 2%ME of tenvermectin used for bamboo cavity injection were developed,and the prevention and control of underground pests was carried out with 4%tenvermectin WG.New molecules compounds with good insecticidal of methylamino tenvermectin benzoate（salt）,acetylamino tenvermectin and lepimectin were discovered by relationship between structure and insecticidal activity.These preliminary results provided useful insight in guiding further modifications of tenvermectin in the development of potential new insecticides for insect pests in the bamboos.