Skin spot

Skin spot is a common fungal disease of potatoes caused by the pathogen Polyscytalum pustulans. This soil-borne fungus primarily affects the tubers, causing surface lesions that negatively impact both the aesthetic quality of the potatoes and their potential for long-term storage.

The disease affects potatoes and is known to persist in the soil for several years. It is most commonly introduced into clean fields through contaminated seed potatoes. Once established, the fungus spreads through spores released from infected tubers or crop debris, especially in environments where soil moisture remains high.

The symptoms of skin spot appear as small, circular, raised spots or pimples on the tuber skin. These spots are often surrounded by a dark, sunken margin. In severe infections, these individual spots may coalesce into larger, roughened patches, which can sometimes look like lesions of other types of common scab, making visual diagnosis complex.

Development and spread of the disease are highly dependent on environmental conditions. Cool, damp weather during the growing season promotes the movement of spores in the soil, leading to the infection of developing tubers. High humidity during storage also accelerates the proliferation of the fungus, leading to significant losses in stored batches.

The economic impact of skin spot is significant for potato producers. While it usually does not destroy the internal flesh of the potato, the damage to the skin reduces the market value of the crop. Additionally, infected tubers are prone to dehydration and secondary bacterial infections, which can result in significant decay during storage or transport.

• Planting certified disease-free seed potatoes.
• Practicing long crop rotation cycles to reduce soil inoculum.
• Ensuring good drainage to avoid waterlogged soil conditions.
• Harvesting in dry conditions to minimize skin damage.
• Ensuring rapid cooling and proper ventilation in storage facilities.