Powdery Scab

Tuber symptoms can vary from shallow depressions to raised scab-like lesions. Lesions at a certain stage of development can be seen to be filled with powdery-looking structures called cystosori, hence the name of the disease, powdery scab.

Causal Agent:

The protozoan called Spongospora subterranea.


Spongospora is a soil-inhabiting organism with a complex life cycle. It can survive in soil without hosts for several years; hosts include many solanaceous relatives of potato including nightshades.

Powdery scab occurs in most potato producing regions in the world, and seems to be getting more prevalent in the Northwest.


Spongospora is easily moved to new locations on seed tubers or in soil.


  1. Avoid planting infected seed into uninfested soil.
  2. Follow good rotation practices of 3 or more years between potato crops.
  3. Grow varieties that show less severe damage and symptoms in infested soil.
  4. There are no effective foliar or soil-applied chemical control options.

Further Reading:

Pacific Northwest Pest Management Handbooks

Consortium Members and Partners


Insects, Diseases, Nematodes, & Beneficial Organisms

Find out more information about insects, diseases, nematodes, and beneficial organisms for Potatoes.

About The Northwest Potato Research Consortium

In February 2012 the state potato commissions in Washington, Idaho, and Oregon officially launched a new cooperative effort in research. The aim of this initiative is to increase cooperation and efficiency of the research programs funded by the three potato commissions that total about $1.5 million annually. It will also work toward comprehensive research results reporting process that aims to get useful information to the growers and industry members who need it. This website is a big part of that effort. Research results, integrated pest management guidance, and production information of many kinds will be presented here. For feedback or suggestions on this site, please contact Andy Jensen, Manager of the Consortium.

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