Plum pox, an invasive disease of stone fruits recently discovered in Pennsylvania is caused by an aphid transmitted potyvirus, plum pox virus (PPV). Here we describe aphid species communities and the seasonal dynamics of the dominant aphid species within two central Pennsylvania peach orchards. To identify potential PPV vectors, we trapped aphids weekly in 2002 and 2003 from April to November. A total of 42 aphid species were identified within both orchards over two years. Species richness ranged from 24 to 30 species based on taxonomic determinations. Based on an abundance-based coverage estimator, species richness was predicted to range from 30-36 species. Three species Aphis spiraecola, Rhopalosiphum maidis, and Myzus persicae were consistently dominant across locations and years. Orchard trapped populations of these three species peaked in a chronological sequence, as listed above. Tests of four trap designs indicated that trap color influenced species distribution in traps and that yellow sticky traps were effective in monitoring aphid immigration into orchards. Based on previously published vector efficiency studies and on the aphid population seasonal dynamics reported here, A. spiraecola is probably the most important PPV vector in Pennsylvania orchards.