POTATO DISEASES

(Spongospora subterranea)

Powdery Scab is  disease caused by Fungi meet while growing potatoes.
It is present in all potato-growing areas in temperate zones and in the tropical highlands of Central and South America.

Symptoms of Powdery Scab

There are usually no aboveground indications of disease. Initial symptoms are small, light-colour, blister-like swellings on the tuber surface. At an advanced stage, these become dark, open pustules 2 to 10 mm in diameter or larger, containing a brown, powdery spore mass.

Lesions are variable in shape, mostly roundish, and fringed by broken skin. Root galls of up to 15 mm across may form. In large numbers, they reduce plant vigour. When galls are newly formed, their colour is similar to that of normal roots.

Later, as galls disintegrate, the colour rapidly darkens.

Management

Soil fumigation with methane sodium is reported to control powdery scab. Planting in well-drained soils free of disease and a long crop rotation with grasses where disease occurs may reduce incidence.

Plant disease free potato tubers. Resistant potato cultivars exist and should be used.

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