White Mold

Infected stems often have fluffy white mold, hence the name of the disease.

Causal Agent:

Sclerotinia sclerotiorum


Pathogen of many crops and other plants. Survives winter and other adverse conditions such as pesticides as sclerotia in the soil. Sclerotia germinate in spring and produce tiny mushroom-like structures called apothecia, which produce ascospores that infect senescing tissues such as flowers. Infections of healthy tissue start from mycelial growth from infected dying plant tissue or directly from sclerotia in the soil.


New fields can be infected by ascospores blown with the wind, but the pathogen is extremely wide spread due to its wide host range and persistence in the soil.


  1. White mold is most serious in fields with dense canopies, plenty of nitrogen fertilizer, and excess overhead irrigation; therefore —
    *manage crop growth to limit canopy density, and
    *avoid excess irrigation and long periods of leaf wetness.
  2. Fungicide applications should be timed to coincide with full bloom of the primary flower clusters.
  3. See the Online Guide to Plant Disease Control for specific fungicide products here.

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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 Raina Spence, Manager of the Consortium.

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