September 13, 2001

Sclerotinia A Problem For Some Canola Growers

Significant sclerotinia stem rot or white mold were found on canola plants especially in Wells and Sheridan counties says Greg Endres, North Dakota State University Extension Service area agronomist."The incidences are higher than we’ve seen in the past few years."

Wells county had an incident average of 40 percent and Sheridan county an average of 38 percent. "In the worst field, 83 percent of the canola stems had sclerotinia" says Endres. "Using Canadian data, the yield loss could reach close to 60 percent due to sclerotinia. That doesn’t account for other diseases."

Sclerotinia stem rot is a fungal disease that can be very destructive especially during periods of wet weather. It can survive up to five or six years in the soil in the form of hard black fungus bodies called sclerotia. The sclerotia germinate to produce tiny mushroom-like bodies which produce millions of airborne spores. Rotted canola stems usually have a bleached appearance.

Fields were also checked for alternaria black spot, aster yellows and blackleg according to Endres. However, sclerotinia was the only disease present at economically significant levels.

This is the 10^th year of canola field surveys according to Art Lamey, professor emeritus, NDSU Extension plant pathology. "We surveyed 24 counties in North Dakota and six in Northwestern Minnesota. There were some areas of concern such as Ramsey county which averaged about 29 percent. However it was less than some counties in central North Dakota."

Survey details will be published in an Extension Service report, available later this fall.

Growers should plan on a three or four year rotation for fields with a history of sclerotinia. Crops that are susceptible to sclerotinia such as crambe, sunflowers, mustard, dry beans, soybeans, garbanzo beans, safflower, field peas and lentils should not be planted in the rotation.

This was also the first year growers could access the sclerotinia risk map says Lamey. "It is meant as a management tool that canola growers can use in making a decision on whether or not to apply fungicide. The map shows regions of North Dakota and Minnesota where conditions are favorable for sclerotinia. Maps and other detailed information is available on the web at http://www.ag.ndsu.nodak.edu/aginfo/sclerotinia/sclerotinia.htm .

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Source: Greg Endres, (701) 652-2951, gendres@ndsuext.nodak.edu
Art Lamey, (701) 231-7056, alamey@ndsuext.nodak.edu
Editor: Rich Mattern (701) 231-6136, Richard_Mattern@ndsu.nodak.edu