Avoid bruising sweet potatoes during digging and storage. Damage from this disease, caused by the fungus Monilochaetes infuscans , is primarily cosmetic. Dark brown to black spots develop on the roots. The spots enlarge and may coalesce. Scurf lesions continue to enlarge when sweet potatoes are placed in storage.
Most scurf infections result from the use of infected propagating material.
The pathogen also survives in soil for one to two years. Disease severity is greater in fine-textured soils and when the organic matter content of the soil is high. The use of animal manure may increase the incidence of scurf. Seed roots should be bedded only in soil free of the pathogen. Remove all plant debris after harvest.