乙基多杀菌素和联苯肼酯对地熊蜂的毒性及风险评估

Toxicity and risk of spinetoram and bifenazate to bumblebee Bombus terrestris(Hymenoptera: Apidae)

【目的】明确乙基多杀菌素和联苯肼酯对地熊蜂Bombus terrestris的毒性,探讨这两种农药亚致死浓度对地熊蜂体内乙酰胆碱酯酶(AchE)、谷胱甘肽-S-转移酶(GST)和羧酸酯酶(CarE) 3种解毒酶活性的影响。【方法】采用饲喂法测定60 g a.i./L乙基多杀菌素和43%联苯肼酯对地熊蜂采集蜂的急性经口毒性,依据农药对蜜蜂生态风险的危害熵(hazard quotient, HQ)值评估这两种农药对地熊蜂的风险。同时测定了这两种农药亚致死剂量(LD_(50)和LD_(80))处理后地熊蜂AchE, GST和CarE的活性变化。【结果】60 g a.i./L乙基多杀菌素和43%联苯肼酯对地熊蜂采集蜂的急性经口毒性测定48 h时LD_(50)值分别为3.590和1 447μg a.i./蜂,其中60 g a.i./L乙基多杀菌素表现为中毒,43%联苯肼酯表现为低毒。两种农药对地熊蜂采集蜂的HQ值均低于50,表现为低风险。LD_(50)和LD_(80)剂量的乙基多杀菌素处理组与对照组相比,3 h时地熊蜂AchE活性被激活,显著高于对照组(P<0.05),分别为对照组的1.45和1.23倍,24 h后活性受到抑制,两个剂量处理组AchE活性均显著低于对照组(P<0.05);CarE活性3 h时同样被激活,显著高于对照组(P<0.05),LD_(50)和LD_(80)剂量处理组CarE活性分别为对照组的1.24和1.53倍, 24 h后活性受到抑制,其中LD_(50)剂量处理组CarE活性显著低于对照组(P<0.05),LD_(80)剂量处理组CarE活性与对照组差异不显著(P>0.05);LD_(50)和LD_(80)剂量处理组GST活性3 h被激活,显著高于对照组(P<0.05),分别为对照组的2.24和2.58倍,24 h后活性降低,但两个剂量处理组GST活性仍显著高于对照组(P<0.05)。43%联苯肼酯处理后,与对照组相比3 h时LD_(50)和LD_(80)剂量处理组AchE活性与对照组差异不显著(P>0.05),24 h后AchE活性降低,显著低于对照组(P<0.05),分别是对照组的75%和80%;CarE活性3 h时被抑制,LD_(50)剂量处理组CarE活性显著低于对照组(P<0.05),LD_(80)剂量处理组CarE活性低于对照组,但差异不显著(P>0.05),24 h后CarE活性被激活,其中LD_(50)剂量处理组CarE活性高于对照组,但差异不显著(P>0.05),LD_(80)剂量处理组CarE活性显著高于对照组(P<0.05);LD_(50)剂量处理组GST活性3 h时被激活,显著高于对照组(P<0.05),24 h后活性降低,但仍显著高于对照组(P<0.05),3 h和24 h的活性分别为对照组的2.04和1.72倍,LD_(80)剂量处理组3 h的GST活性与对照组无显著差异(P>0.05),24 h后活性降低,显著低于对照组(P<0.05)。【结论】乙基多杀菌素和联苯肼酯对地熊蜂的HQ评估均表现为低风险,其中联苯肼酯对地熊蜂的安全性较高,在熊蜂授粉过程中可以按照推荐剂量应用,但过量施用或者长期施用可能会造成熊蜂体内药剂积累引起生理或者行为的变化,乙基多杀菌素在温室及大田授粉期的使用剂量和方法有待进一步研究。

【Aim】 This study aims to clarify the toxicities of spinetoram and bifenazate to bumblebee Bombus terrestris, and to explore the effect of sublethal doses of these two pesticides on the activities of three detoxifying enzymes including acetylcholinesterase(AchE), glutathione-S-transferase(GST), and carboxylesterase(CarE). 【Methods】 The acute oral toxicities of 60 g a.i./L spinetoram and 43% bifenazate to the foragers of B. terrestris were measured by feeding method. The risk of the two insecticides to B. terrestris was assessed based on the hazard quotient(HQ) values for the ecological risk of insecticides to bees. The changes in the activities of AchE, GST and CarE in foragers of B. terrestris treated with the two pesticides at sublethal doses(LD50and LD80) were assayed. 【Results】 The LD50values of 60 g a.i./L spinetoram and 43% bifenazate against foragers of B. terrestris at 48 h after oral exposure were 3.590 and 1 447 μg a.i. per bee, respectively. Spinetoram at the dose of 60 g a.i./L showed moderate toxicity to foragers of B. terrestris, while 43% bifenazate showed low toxicity. The HQ values of the two insecticides to foragers of B. terrestris were both below 50, suggesting that the two insecticides present low risk to this bumblebee species. The AchE activities in bees treated with LD50 and LD80 of spinetoram were significantly enhanced at 3 h(P<0.05), with a 1.45-and 1.23-fold increase as compared to the control group, respectively. Subsequently, the AchE activities in both the dose groups were inhibited after 24 h, and were significantly lower than that in the control group(P<0.05). The CarE activities in bees treated with LD50 and LD80 of spinetoram were also significantly higher in the first 3 h after treatment, being 1.24-and 1.53-fold higher than that in the control group, respectively, and then inhibited after 24 h. At 24 h after treatment, the CarE activity in the LD50 dose group was significantly lower than that in the control group(P<0.05), but that in the LD80 dose group showed no significant difference from that in the control group(P>0.05). The GST activities in bees treated with LD50 and LD80 of spinetoram were also activated at 3 h after treatment(P<0.05), with a 2.24-and 2.58-fold increase as compared to the control group, respectively. At 24 h after treatment, the GST activities in both dose groups decreased, but were still significantly higher than that in the control groups(P<0.05). The AchE activities in bees were treated with LD50and LD80 of 43% bifenazate within 3 h showed no significant differences from that in the control group(P>0.05), but reduced to 75% and 80% of that in the control group after 24 h, respectively(P<0.05). The CarE activities in the both dose groups were inhibited after 3 h. The CarE activity in bees treated with LD50of bifenazate for 3 h was significantly lower than that in the control group(P<0.05), whereas that in bees treated with the LD80 dosage showed no significant difference from that in the control group(P>0.05). The CarE activities in bees treated with LD50and LD80 of bifenazate for 24 h were activated, and the LD80 dose group had a significantly higher level of CarE activity than that in the control group(P<0.05), but the CarE activity in the LD50 dose group showed no significant difference from that in the control group(P>0.05). The GST activities in bees treated with LD50 of bifenazate increased at first(P<0.05), and then decreased. The GST activities in bees treated with LD50 of bifenazate for 3 h and 24 h were 2.04-and 1.72-fold higher than that in the control group, respectively(P<0.05). The GST activity in the LD80 dose group was not significantly different from that in the control group in the first 3 h(P>0.05), but was inhibited after 24 h and significantly lower than that in the control group(P<0.05). 【Conclusion】 The results demonstrate that spinetoram and bifenazate have low risk to the foragers of B. terrestris as judged by the HQ value. The safety of bifenazate to B. terrestris is higher, so it can be used in pollination period according to the recommended dosage and method. However, the excessive and long-term application of bifenazate may affect the physiology and behavior of bumblebees. The dosage and method of application of spinetoram during the pollination period need to be further explored.