potato scab A term that may refer to either common scab or powdery scab. In common scab, caused by Streptomyces scabies, the scabs on the tubers are corky and superficial; the disease is commonest on light soils and in dry conditions. Powdery scab is caused by Spongospora subterranea, and is most common on heavy soils and in wet seasons; the scabs differ from those of common scab in that they are powdery.

potato scab A term that may refer to either common scab or powdery scab. In common scab, caused by Streptomyces scabies, the scabs on the tubers are corky and superficial; the disease is commonest on light soils and in dry conditions. Powdery scab is caused by Spongospora subterranea, and is most common on heavy soils and in wet seasons; the scabs differ from those of common scab in that they are powdery.