Bulletin #2437, Potato Facts: Potato Mop-Top Virus (PDF) By Steven B. Johnson, Extension Crops Specialist, University of Maine Cooperative Extension For information about UMaine Extension programs and resources, visit extension.umaine.edu. Find more of our publications and books at extension.umaine.edu/publications/. History The disease, potato mop-top, is caused by the virus, potato mop-top virus (PMTV). PMTV is