Bulletin #2436, Potato Facts: Powdery Scab of Potatoes (PDF) Steven B. Johnson, Extension Crops Specialist 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 Powdery scab was first found in Germany in 1841 and spread throughout Europe by 1855. It was found in South America