Abstract: In order to evaluate the safety of imidacloprid against Orius sauteri in tobacco fields, the acute exposure toxicity of imidacloprid against Orius sauteri adults and nymphs was determined by the drug film method, and the safety of spraying imidacloprid against Orius sauteri in tobacco fields was evaluated by calculating the hazard quotient（HQ） in farmland. The results showed that the lethal concentration 50 of imidacloprid to the first to fifth instars of nymph and male and female adults of Orius sauteri were 0.587 7, 1.742 1, 2.433 5, 4.401 1, 4.527 8, 6.087 2, 2.942 4 mg（a.i.）/L, respectively. When the maximum recommended dose [45 g（a.i.）/hm²] of imidacloprid was applied once in the tobacco field, the HQ of the adult and the third to fifth instar nymphs of Orius sauteri was lower than 5, and the risk was acceptable; the HQ of imidacloprid on the first to second instar nymphs of Orius sauteri were more than 5, and the risk was not acceptable. When imidacloprid was sprayed twice at the maximum recommended dose [45 g（a.i.）/hm²], the HQ was less than the adult and 5 for the fourth and fifth instar nymphs of Orius sauteri, and the risk was acceptable; for the first to third instar nymphs of Orius sauteri, HQ > 5, the risk was not acceptable. When imidacloptid at the maximum recommended dose range, the inhibition rate of the Orius sauteri hatching was 36.42%, and the risk was acceptable. Therefore, when the combined application of imidacloprid and Orius sauteri were used to control pests, spraying imidacloptid should avoid the peak period of young nymphs （before the third instar） of Orius sauteri.

Key words: imidacloprid, Orius sauteri, toxicity, safety assessment