Within the Pacific Northwest, the Columbia root-knot nematode, Meloidogyne chitwoodi, poses a greater threat to the potato industry than other Meloidogyne species currently present. Meloidogyne chitwoodi has a wider host range, is adapted to cooler temperatures, and produces more severe internal and external defects on potato tubers. Current management strategies to control M. chitwoodi include crop rotations and nematicide application. However, M. chitwoodi has a wide host range and nematicides are costly and environmentally toxic. Since its first identification in 1980, more M. chitwoodi populations with contrasting host ranges have emerged. The first identified population, Race 1, can infect carrot. Alfalfa is a poor host for Race 1 and was used as a rotation crop as a control method. A M. chitwoodi population that infects alfalfa was found five years later and designated as Race 2. Unlike Race 1, Race 2 cannot infect carrot. Resistance against Race 1 and Race 2 was identified and introgressed from the wild potato species, Solanum bulbocastanum, onto potato. The resistance offered by these lines was overcome by the M. chitwoodi pathotype, Roza. The host range of Roza resembles Race 1 in its ability to infect carrot and not alfalfa. A diagnostic tool to differentiate the M. chitwoodi populations is needed to develop effective management strategies to improve potato production. Comparative genome analyses between Race 1, Race 2, and Roza revealed genetically diverse regions. Among the PCR 220 primer sets tested, we have successfully identified race and pathotype specific markers. We have validated their specificity using purified genomic DNA as well as soil samples that possess diverse nematode and microbial DNA. We are currently using the race and pathotype specific markers to determine their prominence within Washington state.