Abstract 【Aim】 This study aims to clarify the toxicity of sulfoxaflor, spinetoram and their mixture to the buff-tailed bumblebee, Bombus terrestris. 【Methods】 The acute oral and contact toxicities of sulfoxaflor, spinetoram and their mixture (1∶1) to the 1 day-old adult workers of B. terrestris were measured by feeding application and topical application methods, respectively, and meanwhile the acetylcholinesterase (AChE) activity was measured. The risk of insecticides to B. terrestris was assessed based on the hazard quotient (HQ) values of the ecological risk of insecticides to bees. 【Results】 The LD50 values of sulfoxaflor, spinetoram and their mixture (1∶1) against adult workers of B. terrestris at 48 h after oral exposure were 2.50, 4.97 and 4.07 μg a.i. per bee, respectively. Sulfoxaflor showed moderate toxicity to adult B. terrestris with the LD50 value of 8.72 μg a.i. per bee at 48 h by contact, and no bumblebees died after acute contact with spinetoram and its mixture with sulfoxaflor (1∶1) at 120 μg a.i. per bee. The HQ values of the three insecticides to adult workers of B. terrestris were all below 50, suggesting that these three insecticides present low risk to this bumblebee. Sulfoxaflor inhibited AChE activity in adult workers of B. terrestris, and its action strengthened with the increase of treatment dosage. After the adult workers of B. terrestris were treated with spinetoram and the mixture (1∶1) at LD60, the AChE activities were enhanced first and then inhibited. 【Conclusion】 Sulfoxaflor, spinetoram and their mixture (1∶1) show low risk to adult workers of B. terrestris as judged by the HQ value. The poisoning effects of spinetoram and its mixture with sulfoxaflor (1∶1) are slower than sulfoxaflor, and their safety is higher than that of sulfoxaflor in laboratory safety evaluation.
ZHOU Hao,SHAO Ju-南,DI Yi-Fan et al. Toxicity and risk assessment of sulfoxaflor, spinetoram and their mixture to Bombus terrestris (Hymenoptera: Apidae)[J]. ACTA ENTOMOLOGICA SINICA, 2017, 60(7): 809-816.