Sweet potato foot rot

Taxonomic position and pathogen nature. Plenodomus destruens (formerly known as Phoma destruens) is a fungal pathogen classified within the Ascomycota division. It is a significant phytopathogen specifically known for causing foot rot disease in sweet potatoes, leading to severe decay of storage roots and stem tissues, often resulting in massive economic losses in agricultural production.

Diseases and host crops. The primary disease caused by this fungus is known as foot rot or dry rot. It affects the base of the stem and the tuberous roots of sweet potatoes. The pathogen infects the plant tissue, resulting in necrotic lesions that progress into a dry, corky rot. In advanced stages, the internal tissue of the root turns brown and becomes brittle, severely compromising the nutritional value and marketability of the crop.

Biology and life cycle. The pathogen produces pycnidia, which are structures containing conidia that facilitate the spread of the infection. The fungus is soil-borne and can survive in infected plant debris or in the soil for several growing seasons. Primary infection typically occurs through contaminated planting material (slips) or via spores transported by water, rain splashing, or contaminated farming tools.

Conditions for development and harmfulness. Disease development is favored by cool to moderate temperatures combined with high soil moisture. The fungus is most destructive during the storage phase, where a single infected tuber can serve as an inoculum source for an entire storage batch if humidity is not controlled.

• Severe reduction in crop quality and shelf life.
• Loss of seed material for the following season.
• Infection of previously healthy neighboring tubers in storage.

Management and control measures. Management strategies include the use of certified, disease-free propagation material and careful selection of land with no history of the pathogen. Crop rotation is essential to break the life cycle of the fungus in the soil. Post-harvest, it is critical to ensure proper curing of the tubers and storage in a cool, well-ventilated environment to suppress the progression of rot.