Scurf of sweet potato

Scurf is a fungal disease of sweet potato caused by the pathogen Monilochaetes infuscans. This soil-borne fungus primarily attacks the surface of the storage roots, making it a major concern for growers who prioritize the aesthetic and commercial quality of their harvest.

The disease exclusively affects sweet potatoes (Ipomoea batatas). It is most commonly introduced into clean fields through contaminated vegetative slips used for planting. Once established in the soil, the fungus can persist for several years, acting as a recurring source of infection.

The primary symptom is the appearance of brown or dark-grey, patchy discolouration on the skin of the sweet potato roots. These spots are strictly superficial, meaning they do not affect the internal quality or flavor of the root, yet they significantly lower the market value of the produce.

Environmental conditions play a crucial role in the development and spread of scurf. Moist, cool to moderately warm soil conditions favor the growth of the fungus. Poor drainage and high soil moisture levels during the growing season significantly increase the incidence and severity of the disease.

The damage caused by scurf is primarily cosmetic but economically significant. The compromised periderm of the root makes the potato more susceptible to moisture loss during storage, leading to shrinkage. Furthermore, affected potatoes are often rejected by consumers, resulting in reduced profitability.

• Planting certified disease-free sweet potato slips.
• Implementing a long-term crop rotation cycle to reduce soil pathogen load.
• Ensuring proper field drainage to prevent waterlogged soil conditions.
• Sanitizing all harvesting and storage equipment to prevent cross-contamination.
• Selecting tolerant varieties that show resistance to the pathogen.