scurf of sweet potato

Scurf-Symptoms include a discoloration of the skin which is mostly superficial. However, this discoloration affects marketability and cannot be determined until harvest. 

Figure 1. Scurf of sweet potato. Note gray, brown stain on surface. Holes are not necessarily a symptom of scurf. Figure 1. Scurf of sweet potato. Note gray, brown stain on surface. Holes are not necessarily a symptom of scurf.
Figure 2. Scurf of sweet potato. Note gray, brown stain on surface. Figure 2. Scurf of sweet potato. Note gray, brown stain on surface.
Figure 3. Scurf of sweet potato. Figure 3. Scurf of sweet potato.
Figure 4. Scurf of sweet potato. Figure 4. Scurf of sweet potato.