Scurf on sweet potato. Photo by Charles Averre, NC State University through Bugwood.org.
If you plan to grow sweet potatoes this year know that it is easier to try to prevent scurf rather than trying to eradicate it when it infects your crop and fields.
The soil borne fungus Monilochaetes infuscans causes scurf of sweet potato. It only affects the below-ground portion of the sweet potato plant. This fungus has a very limited host range - sweet potato and morning glories. Because scurf will only survive in the soil for one or two years the main cause of the disease is use of infected planting material. The fungus will overwinter on infected roots and will spread to slips produced from these roots. It can also spread from infected to healthy roots during storage.
Scurf can be effectively managed with a few specific production practices. These include:
- Use scurf-free sweet potatoes for slip production
- Dip seed roots for 1-2 minutes in a fungicide solution (Mertect 340F @ 8.0 fl. oz. per 7.5 gal. water) and plant immediately
- Use disease-free beds for slip production and maintain soil temperatures at 80-85°F.
- Cut slips at least 1" above the soil line to avoid spreading any disease present to the field
- Allow 3 to 4 years between sweet potato production in a field whenever possible, especially in fields known to be infected
- Thoroughly clean and disinfect harvest bins and storage areas before harvest and storage of your new crop
- Avoid bruising roots during harvest and maintain a curing temperature of 80-85°F. Do not allow storage temperature to fall below 55°F and maintain the relative humidity at 85-90% during curing and storage