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Powdery Scab

Powdery Scab - spongospora subterranea is caused by a fungus and generally affects potatoes and tomatoes, and is generally more prevalent when grown in cool moist/damp conditions, and or heavy soils.

This pathogen invades the tuber through wounds and sometimes the eyes, and appears as small raised pimples beneath the skin of the tuber /fruit.

These symptoms look similar to common scab, although they are usually smaller, more uniform in size, and surrounded by a fringe of potato skin.

The pimples grow and eventually burst open, and produce masses of dark brown powdery spore balls.

As the spores are dispersed they leave shallow depressed lesions (scabs)

Light attacks do not tend to damage the tubers /fruit too much, however, severe attacks can render them unfit to eat.

There are no other effective controls for powdery scab, the best control is to practise crop rotation, and only plant unblemished disease free seed potatoes.





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