Residual Behavior Of Thiamethoxam And Carbendazim During The Formation Of Bee Bread And Honey And Exposure Assessment For Apis Mellifera Ligustica Spin Larvae

Bees are the most important pollinators.The phenomenon of colony collapse disorder(CCD)has caused people to attach great importance to the health and safety of bees.The irrational use of long-term chemical pesticides is considered to be the most important factor causing this phenomenon.Based on the monitoring data of pesticide residues in bee products nationwide for 4 years,thiamethoxam and carbendazim,which have high detection rates,were selected as representative pesticides in this paper to study their residual behaviors during the formation of pollen(nectar)-bee bread(honey),evaluate the effects of pesticide treatment on foraging behavior(orientation behavior,sugar perception behavior)and the growth and development of larvae of Apis mellifera ligustica,and quantitatively analyze the intake and exposure risks of larvae of Apis mellifera ligustica.The research results have important theoretical guiding significance and practical application value for strengthening the risk management of pesticide residue pollution in honey plants,protecting bee colony health and enriching the theories and methods of pesticide environmental risk assessment.The main research results are as follows:1.The multi-residue analysi methods validation for thiamethoxam,carbendazim and their metabolites in five substratesThe results showed that thiamethoxam,carbendazim and their metabolites clothianidin,benzimidazole and 2-aminobenzimidazole had a good linear relationship in the concentration range of 2.5-200 ?g/kg,and the correlation coefficient(r)was 0.9984-0.9994.Limits of detection(LODs)and Limits of quantitation(LOQs)of the method were 0.22-0.57 ?g/kg and 0.72-1.91 ?g/kg,respectively.The average recovery rate of thiamethoxam and its metabolite clothianidin in rape pollen,bee bread,nectar,honey sac and honey was 73.4-112.3%,and the relative standard deviations(RSDs)was 1.2-13.3%.The average recovery rate of carbendazim and its metabolites benzimidazole and 2-aminobenzimidazole was 75.1-1 18.3%,and RSDs was 1.4-17.6%.The accuracy,precision and sensitivity of the method can meet the requirements of pesticide residue analysis.2.Residual behavior of thiamethoxam and carbendazim during the formation of pollen-bee breadThe residual behavior of tested pesticides during the formation of pollen-bee bread was studied by detecting the residues of thiamethoxam and carbendazim in the pollen collected at the entrance of the hive and the fermented bee bread which brought the pollen back to the empty spleen of the hive on the same day.The results showed that the residues of thiamethoxam and carbendazim in pollen were higher than those in bee bread at the same sampling time,and the residue levels of thiamethoxam on the two substrates were significantly different(1.35-2.60 times);The residues of thiamethoxam metabolite(clothianidin)and carbendazim metabolite(benzimidazole,2-aminobenzimidazole)in bee bread showed a trend of increasing first and then decreasing with time.The residual level of clothianidin was relatively high(32.05±1.55?g/kg)on the 8th day after application.The residual amounts of benzimidazole and 2-aminobenzimidazole on the 14th day after application were relatively high,which were 94.08±1.1 ?g/kg and 16.23±1.04 ?g/kg,respectively.3.Residual behavior of thiamethoxam and carbendazim during the formation of nectar-honey sac-honeyThe residues of thiamethoxam and carbendazim in nectar of rape flower,honey sac collected from bees and fermented honey collected on the same day to bring nectar back to the empty spleen of honeycomb were detected,and the residual behavior of tested pesticides during nectar-honey sac-honey formation was studied.The results showed that the residue level of thiamethoxam in nectar was 1.90-4.19 times of that in honey sac at the same time,with significant difference(p<0.05),while the residue level in honey sac and honey was not significant difference.The residual level of carbendazim in nectar was 1.23-4.49 times higher than that in honey sac and 1.48-2.40 times higher than that in honey.The residues of thiamethoxam metabolite clothianidin and carbendazim metabolite benzimidazole in honey showed a trend of increasing at first and then decreasing with the collection time.The residual level of clothianidin was relatively high(2,63±0.09 ?g/kg)on the 8th day after application,while the residual level of benzimidazole was relatively high on the 14th day after application,which was 4.48±0.17 ?g/kg,and 2-aminobenzimidazole was not detected.4.The effects of thiamethoxam and carbendazim on the growth and development of the Apis mellifera ligustica larvaeThe effects of thiamethoxam and carbendazim on the growth and development of Apis mellifera ligustica larvae were evaluated.The results showed that the pupation rate and eclosion rate of Apis mellifera ligustica larvae could be reduced by 30%and 40%,respectively,after 44 ng/g thiamethoxam treatment.However,the pupation rate and eclosion rate of Apis mellifera ligustica larvae treated with 15 ?g/g carbendazim were not significantly different from those of the control.5.Risk assessment of thiamethoxam exposure to Apis mellifera ligustica larvaeAs the toxicity of carbendazim to Apis mellifera ligustica larvae is low,this paper only evaluates the exposure risk of thiamethoxam to Apis mellifera ligustica larvae(1-3 day-old).Risk assessment of bee larvae was carried out by using NOEC(No observed effect concentration)and residual ratio method recommended by EFSA(European food safety authority).The results showed that the risk quotients were 2.10,1.68 and 1.25 at 4 d,6 d and 8 d after application,respectively,indicated that bees should not be put into the environment within one week after thiamethoxam application.The risk quotient is less than 1 after 11 d of application,and the risk is within the acceptable range.