Hairy nightshade, Solanum sarrachoides (Sendtner), a solanaceous weed found in the Pacific Northwest hinders potato, Solanum tuberosum (Linnaeus) cultivation by acting as a reservoir of Potato leafroll virus (PLRV) and its vector the green peach aphid, Myzus persicae (Sulzer) (Aphididae: Homoptera). Preliminary sampling data on potato and hairy nightshade revealed greater populations of M. persicae on S. sarrachoides. The biology and behavior of M. persicae on S. sarrachoides and S. tuberosum with and without PLRV-infection were studied. Life history parameters including nymphal period, daily fecundity and adult longevity were monitored at 24- hour intervals. Experiments were also conducted to test aphid behavioral responses to S. sarrachoides and S. tuberosum with and without PLRV-infection. Emigration rates monitored from the vicinity of the treatment leaflets at 10-minute intervals revealed that PLRV-infection increased the attraction and arrestment of wingless M. persicae. Immigration by wingless M. persicae was also measured by a bioassay comparing S. sarrachoides and S. tuberosum with and without PLRV-infection.