Abstract: By the method of high performance liquid chromatography,the decomposition of avermectin after adding ultraviolet absorbents was studied under the ultraviolet intensity of 420 lx.The results showed that under the ultraviolet,the decomposition rate of avermectin after adding UV-73 and UV-75 decreased 76.74% and 77.46% after 4 hours,37.92% and 47.09% after 8 hours,33.55% and 48.55% after 16 hours,and 23.57% and 42.09% after 24 hours,respectively.The synergism ratios of avermectin with UV-73 and UV-75 on diamondback moths in laboratory were 1.59 and 1.74,respectively,and the enhanced control effects of UV-73 and UV-75 were also higher than that of single avermectin application in the field.

Key words: Avermectin B_1a, Soil microorganism, Earthworm, Acute toxicity