Choose light soils. Do not plant sweet potatoes more than once every 2 to 4 years on the same plot of land. If scurf is present in the soil and a long rotation cannot be practised, reduce the disease level by fumigating with metham sodium. Do not store in the ground. The fungus Fusarium causes the sweet potato roots to rot.
Roots develop soft spots, which gradually enlarge.
It affects some varieties more than others, and causes most damage in storage. In the field, the rot often starts when the roots have been damaged by cold or wet soils. It progresses rapidly within the root and, under favourable conditions the whole root may break down in a few days. Harvesting Roots are ready for harvesting 14 to 20 weeks after planting, but can also be ground-stored in the soil when mature. Periodically, dig a few roots to check their maturity.