In recent years, leafhopper-transmitted phytoplasma diseases of potato, Solanum tuberosum L., have become increasingly important in many production areas worldwide. Serious epidemics of purple top disease of potato, caused by phytoplasma infections, have occurred in North and Central America and Central and Eastern Europe. Countries severely affected by phytoplasma diseases of potato include the United States, Mexico, Guatemala, Russia, and Romania. These emerging potato diseases are causing significant yield losses and a reduction in tuber and seed quality. Accurate identification of phytoplasmas involved in the disease and their insect vectors, in addition to a better understanding of disease epidemiology and vector population dynamics, are essential to effective management of phytoplasma diseases in potatoes. A case study of identification, epidemiology, and management of leafhopper-transmitted phytoplasma disease of potatoes in the Pacific Northwest of the United States is presented herein.