品北农林升枚大学 NORTHW国图T A&F UNIV到RsIT型 English grain aphid is a migratory pest.Northern limit is located at 26- 27 N.There are no overwintering aphids in northern China in winter. 888880English grain aphid is a migratory pest. Northern limit is located at 26- 27 °N. There are no overwintering aphids in northern China in winter