The species Aphis nasturtii is commonly known as the buckthorn aphid and is common to regions of potato growing from Manitoba eastward. The buckthorn aphid infests the lower leaves of the potato plant. The aphid rarely increases in numbers sufficiently to weaken a crop or reduce potato yields; however, the species is known to harbour viruses, in particular, the Potato Virus S (PVS) and Potato Virus Y (PVY). The aphic overwinters as an egg on buckthorn.
Adults range from 1.2 mm to 2 mm in length, the body is flattened, egg-shaped, lemon-yellow or green, the tip of the abdomen (cauda) has fewer than 10 hairs (setae), and the antennae do not have prominent tubercles at the base. Winged adults have a conspicuous dark brown to black head and thorax.
When scouting for the buckthorn aphid, the use of at least a 10X hand-held magnify glass is required in order to distinguish it from other species of Aphis. Key distinguishing features of this species are a fairly flattened body, antennae shorter than the overall length of the body and their black colour in the autumn time towards the end of their life cycle in the crops.