Acta Entomologica Sinica ›› 2019, Vol. 62 ›› Issue (3): 334-342.

• RESEARCH PAPERS •

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

WANG Huan, XU Xi-Lian*

1.  (Institute of Plant and Environment Protection, Beijing Academy of Agriculture and Forestry Sciences, Beijing 100097, China)
• Online:2019-03-20 Published:2019-03-14

Abstract: 【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 LD50 and 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 LD50 of 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 LD50 and 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.