Scurf

Scurf is a fungal disease caused by the pathogen Monilochaetes infuscans. This disease primarily affects sweet potatoes, causing cosmetic damage to the skin of the storage roots. While the internal flesh of the vegetable usually remains edible, the surface discolouration significantly reduces the marketability of the product.

The pathogen is soil-borne and can persist in fields for several years, especially if crop debris is not properly managed. It primarily infects the underground parts of the plant, including the roots and the base of the stems, leading to brown or black blotches on the skin of the tubers.

Visual symptoms appear as dark, circular or irregular spots on the tuber surface. These lesions can merge over time, eventually covering large portions of the root. In some cases, the skin may become roughened, and the lesions can provide entry points for other decay-causing fungi during the storage phase.

Development of the disease is favored by high soil moisture and moderate temperatures. The fungus thrives in heavy, poorly drained soils, and spread is often accelerated by excessive irrigation or rainfall during the tuber enlargement stage of the growing season.

Management of scurf requires an integrated approach focusing on prevention:

• Use certified, disease-free sweet potato slips for planting.
• Implement a strict crop rotation cycle of at least 3 to 4 years.
• Improve soil drainage to prevent conditions that favor fungal proliferation.
• Thoroughly sanitize cultivation equipment after working in infested areas.
• Select resistant or tolerant varieties if available in your region.