Research Of Milbemycins Acaricidal Activity And Stability

Milbemycins which is regarded as a new biological pesticide,with the features ofbroad-spectrum,high efficience,low toxicity,together with abamectin are praised as theinsecticides with the highest effects now.This paper studies active characteristics of milbemycinon the various development stages of carmine spider mite population, also studies the stability ofthe preparation,and develops milbemycin to be green biological pesticide.The contents andresults were summarized as follows:1. The active effect of milbemycin on the various development stages of carmine spider mitepopulation was systematically tested by leaf disc spray. The toxicities of milbemycin in LC50values for larva mites, female adult and eggs were0.0376、0.1860、0.8393mg/L，when it was0.8mg/L, the inhibitive effect on oviposition of female adult mites of milbemycin were82.56%.Itis tested by seeding outdoor spot activity, when the concentration of milbemycin was2mg/L, theacaricidal activity reached96.89%24h later..2. Using the alcohol and turpentine as solvents,2%milbemycin Turpentine and2%milbemycin Turpentine EC were arranged,and the decomposition rates of the two solventsunder strong sunlight and ultraviolet light were tested.Under the condition of1200-1500Lxlight,the degradation rate of2%milbemycin ethanol EC was apparently higher than that of2%milbemycin Turpentine EC.And with the increase of illumination time,the degradation rateaccelerated obviously.After12h, the degradation rate of2%milbemycin ethanol EC reached98.37%,but2%milbemycin Turpentine EC just28.72%,after72h, the degradation rate of2%milbemycin Turpentine EC reached48.61%,2%milbemycin ethanol EC reached99.17%. Underthe condition of254nm、420LX UV light irradiation, after72h, the UV degradation rate of2%milbemycin ethanol EC closed to100%,but that of the2%milbemycin Turpentine EC reachedonly17.76%.3. The stability of the cold and thermal storage of the preparation shows: the degradation rate ofeffective components was less than5%after cold and thermal storage,both with transparence,uniform appearance, and no precipitation,HPLC analysis shows the degradation rate of effectivecomponents after cold and thermal storage,2%milbemycin ethanol EC were2.72%、1.22%,2%milbemycin Turpentine EC were3.05%、4.67%,both accorded with the requirements of the cold and thermal storage of the preparation4. Lethal effect and synergism of milbemycin with using Turpentine oil as solvent on carminespider mite were tested by leaf disc spray,and GC-MS was used to analyse its composition. Thetoxicities of milbemycin EC arranged for the solvent by the Turpentine oil in LC50values forfemale adult was0.0314mg/L, the co-toxicity coefficient to the milbemycin EC was442.68.GC-MS Analysis showed its main ingredients were alpha pinene,(R)-ouni ene, camphene and3-carene terpene compounds. Terpene compounds had good fat soluble and strong osmosis to theinsect cuticle which was the main reason of abamectin’s having synergistic effect onmilbemycin.Turpentine oil enthanced the stability of milbemycin to sunlight、UV light irradiation、cold and thermal storage,which has significant synergistic effect on acaricidal activity.