Scab

Scab may refer to:
 * Common scab (Streptomyces scabies) - A common disease of potatoes causing skin blemishes.
 * Powdery scab (Spongospora subterranea) - A less common disease of potatoes causing powdery raised patches.
 * Gummosis (Cladosporium cucumerinum) - A condition of cucurbits, especially cucumber, which causes oozing sunken spots on the fruit.