Potato Scab Information

Potato Scab Information

By Josie Borlongan, Garden Guides Contributor
diseased potatoes

About Potato Scab

Potato scab is caused by a soil­borne organism that is worldwide in distribution. The fungus is called Streptomyces scabies and dwells on sandy, light soils with low organic matter content. The same organism also attacks many other root crops as well as the fleshy roots of weeds.

Prevention and Control

Improve soil texture by improving the organic matter and avoiding liming; water regularly since there is a link between scab and dry soil. Avoid planting potatoes on soil that has recently been used for Brassicas. Alkaline soils have more Streptomyces compared to acidic soils.

Grow resistant cultivars, such as Menominee, Ontario, Cayuga, and Seneca.

Affected Plants



Raised, scabby patches develop on the skin of the tubers that can cause the skin to rupture. Damage is superficial only but can cause cracks and can disfigure the tuber. The flesh is not damaged and can be consumed safely; however, the damage is to the agriculture business, since consumers would prefer to buy tubers that do not have scabs.

Other Methods of Control

* Rotate root crops to avoid the buildup of aggressive scab strains.
* Purchase certified potato seed pieces. Do not save tubers from the garden for use as seed.
* Keep soil wet.
* Use acidic fertilizers.
* Test the pH of the soil and apply elemental sulfur to lower the soil pH to 5.2.

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