Bulletin #2445, Potato Wart (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/. Potato wart or potato canker is a disease caused by the soil-borne chytrid fungus Synchytrium endobioticum. It is a serious