Abstract: 【Aim】 This study aims to assess the toxicity and hazard of six neonicotinoid insecticides to Osmia excavata. 【Methods】 The acute oral and contact toxicities of six neonicotinoid insecticides, i.e., acetamiprid, thiamethoxam, sulfoxaflor, imidacloprid, clothianidin and dinotefuran, to the female adults of O. excavata at 24 h and 48 h after treatment were measured by feeding application and topical application methods, respectively. The risk of insecticides to O. excavata was assessed based on the hazard quotient (HQ) values of the ecological risk of insecticides to bees. 【Results】 In oral toxicity assay, sulfoxaflor showed the highest toxicity to the female adults of O. excavata while thiamethoxam showed the lowest toxicity. In contact toxicity assay, clothianidin showed the highest toxicity to the female adults of O. excavata, while sulfoxaflor showed the lowest toxicity. Acetamiprid, thiamethoxam and imidacloprid presented medium risk to O. excavata, while clothianidin presented high risk. And sulfoxaflor and dinotefuran presented medium risk to O. excavata by contact but high risk by oral exposure. 【Conclusion】 The six neonicotinoid insecticides assessed in this study present high risk to the female adults of O. excavata. It should be cautious to use acetamiprid, thiamethoxam and imidacloprid during florescence, and the use of clothianidin, sulfoxaflor and dinotefuran should be avoided in the orchard.

Key words: Osmia excavata, neonicotinoid insecticide, toxicity, feeding application, topical application, hazard assessment