Many studies have evaluated transmission abilities of laboratory-reared aphids for potato virus Y (PVY), but few have focused on PVY-harboring species of field-collected aphids and the strains of PVY harbored by aphids. In the present study, we collected alate aphids in yellow pan traps in potato fields with Japanese commercial cultivars in Hokkaido, northern Japan in single 24-h periods during the tuber bulking stage and examined whether individual whole aphids harbored PVY by nested RT-PCR. PVY-positive individuals were identified to species using the gene sequence for cytochrome c oxidase subunit I and, when needed, morphological data and distribution records. In addition, individual strains of PVY harbored were determined using partial sequences of coat protein. Among 1,857 aphids trapped, 195 aphids had PVY and comprised 19 species; 17 species were identified to species-group taxa. Most of the aphid species detected as PVY positive colonize weeds that are common around potato fields in Hokkaido. Five species-group taxa had not been reported previously as a vector aphid of PVY and might be new PVY-vector species. PVY^NTN was most frequently detected from PVY-positive aphids as found recently in PVY-infected potatoes in commercial fields in Hokkaido. Two or three PVY strains were rarely detected from a single aphid, and no obvious difference was found in the proportion of the harbored PVY strains among positive aphid species. The first documentation of the species composition of PVY-harboring aphids and the strains of PVY harbored in East Asia should aid understanding of the epidemiology of PVY in Japan.