The potato psyllid, Bactericerca cockerelli (Sulc) is becoming increasingly important as Zebra Chip (ZC) continues to cause losses to potato growers. Although the exact cause of ZC is not yet known, it may be related to the toxicity of psyllid feeding, pathogens transmitted by insect vectors, or a combination of factors. Different combinations of these factors have been shown to produce ZC-like symptoms in preliminary laboratory settings. The species has been shown to contain at least two putative biotypes, which may have different toxicity profiles and different abilities to transmit possible pathogens. The identification of psyllids is further confused by migration of populations over long distances. In this study, we (1) characterize the different populations of psyllids, especially in the central United States, Mexico and Guatemala using ISSR fragment data (2) correlate the different populations with geographical locations at specific times to elucidate migration patterns and, (3) characterize the ability of each biotype to cause ZC symptoms. Each of these should help growers more effectively target treatments to the organisms that are doing the most damage.