Abstract: 【Aim】 This study aims to clarify the survival rate and response to rapid cold acclimation in the grain aphid, Sitobion avenae, under extremely low temperature so as to provide a basis for the study of cold tolerance and accurate prediction of this insect. 【Methods】 The supercooling point and freezing point of the laboratory population of S. avenae at various developmental stages were determined, the survival rates of the 1st instar nymphs and the apterous adults exposed to extremely low temperature from -7℃ to -11℃ for 3 h and those exposed to lethal temperature for 3 h after cold acclimation at 0℃ for 1-5 h, respectively, and then transferred to 15℃ for 72 h, were assessed, and the population dynamics of S. avenae was investigated during the whole wheat growth period in Yangling, Shaanxi, northwestern China. 【Results】 The supercooling points of the 1st and 2nd instar nymphs of S. avenae showed a small fluctuation from -27.4℃ to -19.2℃ and from -27.3℃ to -18.3℃, respectively, while those of the 3rd and 4th instar nymphs and adults showed a large fluctuation from -27.4℃ to -10.7℃, from -26.7℃ to -12.5℃, and from -26.7℃ to -11.2℃, respectively. The supercooling point and freezing point of S. avenae increased significantly with the increasing instars. The supercooling point of adults was significantly higher than those of the 1st and 2nd instar nymphs. There were no significant differences in the supercooling points of the 3rd and 4th instar nymphs and adults between the alate and apterous morphs at the same developmental stage. The analysis of survival rate at low temperature showed that the lethal temperatures (80% mortality) for the 1st instar nymphs and apterous adults remained around -10.5℃ and -8.1℃, respectively. The rapid cold acclimation at 0℃ improved significantly the survival rate of the 1st instar nymphs and apterous adults at extremely low temperature, with the highest survival rate after cold acclimation for 2 h. The results of field investigation from 2018 to 2019 revealed that S. avenae could overwinter as parthenogenetic nymphs and adults in Yangling, Shaanxi. 【Conclusion】 S. avenae shows strong low temperature adaptability. Its parthenogenetic aphids can overwinter successfully in Yangling, Shaanxi. These results suggest that aphids in the wheat field in early spring may source partly from the survived locally overwintering individuals of this aphid.

Key words: Sitobion avenae; cold tolerance, cold acclimation, supercooling point, survival rate, parthenogenetic aphid, population dynamics