Scurf-infected sweet potatoes are more susceptible to invasion by other fungi. Sweet potatoes with symptoms of scurf. Scurf lesions continue to enlarge when sweet potatoes are put into storage, and new lesions appear if high relative humidity is maintained. The optimum temperature for disease development is 75 degrees F, but scurf can develop to a lesser extent over a wide range of temperatures. Disease development is greatest when soil moisture is optimal for plant growth.
Most scurf infections result from the use of infected propagating material.
The fungus can also survive in crop debris in the soil for 1 to 2 years. Disease severity is greater and persistence of the pathogen longer in fine-textured, highly organic soils. The disease has a narrow host range that consists only of species in the genus Ipomoea . Bed these in soil free of the disease. Cut transplants at least 1 inch above the soil line, and dip them in a fungicide.