| In recent years,the use of neonicotinoid insecticides to control pest damage has increased crop yield,improved product quality,and promoted global agricultural productivity in global.In this paper,the residual degradation behavior of thiamethoxam,furamethoxam and flupirofuranone on cucumber flowers,leaves and their acute oral and acute contact toxicity to honeybees were studied to comprehensively analyze and evaluate the risk of these three kinds of insecticides to bees.The results of this study are as follows:(1)Three new methods for the determination of neonicotinoid insecticides were established.The methods of detection by ultrahigh performance liquid chromatography-tandem mass spectrometry(UPLC-MS/MS)and analysis of thiamethoxam,dinotefuran and flurafrufurone in cucumber flowers,leaves were established.(2)The residu behaviors of three pesticides on cucumber flowers and leaves were determined.Under the three dosages,the residues on flowers and leaves showed a downward trend with the increasing of time,and the residual amount was proportional to the dose of prinming application.The degradation half-life of thiamethoxam,dinotefuran and flurafrufurone on flowers and leaves was 1.56～2.35 days,1.48～3.77 days and 1.21～2.42 days,respectively.When the dose of priming application of pesticide was the same,the residue on cucumber leaves was higher than that on the flowers.The longest digestion half-life of the three pesticides on flowers was 1.86 days,3.77 days and 2.06 days,respectively,and the residual period were not long.The maximum residues of the three pesticides on flowers were 1.15mg/kg,8.97mg/kg and 8.84mg/kg respectively,which were relatively high.(3)Acute toxicity of thiamethoxam,dinotefuran and flurafrufurone to Apis mellifera L.was determined.The results showed that the acute oral toxicity and acute contact toxicity of three pesticides were thiamethoxam>dinotefuran>flurafrufurone.The acute oral toxicity and the acute contact toxicity of flupirofuranone(active and preparations)to honeybees were "moderate toxicity" and "low toxicity",respectively.The other two pesticides were "high toxicity" to honeybees at both levels of acute oral and acute contact toxicity.(4)The risks of thiamethoxam,furamethoxam and flupirofuranone on honeybees were evaluated.When the end point selected the most sensitive value of EFSA report,the RQ of thiamethoxam dinotefuran and flurafrufurone for bees were 162.1～318.2,173.2～663.5 and 2.0～4.6,respectively.The risks of the three pesticides were not acceptable.When the end point selected the most sensitive value of toxicity data in this study,the RQ of thiamethoxam dinotefuran and flurafrufurone for bees were 202.6～397.7,82.3～315.2 and 0.4～0.9,respectively.The risks of flurafrufurone to bees were acceptable,while the risk of thiamethoxam and dinotefuran to honeybees were unacceptable.(5)The results showed that the safety intervals of three pesticides on cucumbers to honeybees was determined.The risk of low-dose thiamethoxam to honeybees was acceptable 10 days after application.The risks of middle dose and high dose 14 days after application were also acceptable.However,the risk to honeybee was unacceptable when low dose of dinotefuran was applied for more than 10 days.The risks of middle dose and high dose after application for more than 21 days were also unacceptable.The risk of low dose of flurafrufurone to honeybees was acceptable after application for two hours.The middle dose and high dose were applied for 1 day,and the risk to bees was acceptable.To sum up,when three kinds of neonicotinoids were sprayed on cucumbers,flurafrufurone had lower risk to be used with low risk to bees,compared with thiamethoxam and dinotefuran.Therefore,in the use of pesticides with high risk to bees,especially in honey crops,especially to nectar and pollen crops,users should try to avoid bee colonies,or take risk reduction measures,such as setting up signs,informing the farmers surrounding bee farmers in advance. |
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