Potato virus Y (Potyvirus: Potyviridae) (PVY), the most economically important virus affecting the seed-potato production in the United States, is vectored by several potato colonizing and non colonizing aphid species in a non persistent manner. Transmission of PVY by Myzus persicae, Macrosiphum euphorbiae and Rhopalosiphum padi (Homoptera: Aphididae) from two sources of virus inoculum was monitored under field conditions during the summers of 2006 and 2007. The inoculum sources were potato, Solanum tuberosum (Linnaeus), and hairy nightshade, Solanum sarrachoides (Sendtner), an annual solanaceous weed occurring in potato fields in Idaho. Eight treatments consisting in the combination of vector species and inoculum sources were replicated three times and evaluated. Potato plots were caged to prevent the effect of external factors. Initial infection and spread of the disease was evaluated through weekly leaf samples processed with DAS-ELISA. In summer 2006 transmission of PVY by the three aphid vectors was higher in plots that had a PVY infected hairy nightshade plant as source of virus inoculum when compared to plots that had a PVY infected potato plant. Both M. persicae and M. euphorbiae transmitted PVY at higher rates than R. padi, regardless of the inoculum source. Results from summer 2007 will also be presented. This information could further expand our understanding of PVY epidemiology in the potato pathosystem