Polyscytalum pustulans

Polyscytalum pustulans is a fungal plant pathogen belonging to the division Ascomycota. It is the causal agent of skin spot disease in potatoes. This pathogen specifically targets the tubers, stolons, and roots, impacting the aesthetic quality and physiological health of the crop, especially when intended for seed production.

The disease manifests as small, dark, raised lesions or pustules on the skin of the potato tuber. These spots can remain isolated or coalesce, covering larger areas of the tuber surface. While the infection typically remains superficial, it can suppress bud development (eyes) on seed tubers, leading to poor emergence and reduced stand density in the following season.

The life cycle of the pathogen involves survival in the soil as a mycelium or through sclerotia-like structures. It can persist in the soil for several years even in the absence of a host. Infection primarily occurs during the growing season when tubers come into contact with the fungus in the soil, often facilitated by cool and wet environmental conditions.

The spread and development of Polyscytalum pustulans are heavily influenced by environmental factors. High soil moisture combined with temperatures in the range of 15°C to 18°C provides an ideal environment for spore germination and infection. Poor soil drainage further exacerbates the issue, creating microclimates conducive to rapid fungal colonization.

To effectively manage and control skin spot, integrated crop management is essential. Key strategies include the exclusive use of pathogen-free seed tubers and strict adherence to crop rotation cycles to reduce soil-borne inoculum. Furthermore, ensuring good soil structure to improve drainage and maintaining a dry environment during tuber storage are critical steps in mitigating the impact of this disease.