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Title: Reducing crown and root diseases of alfalfa for improved yield and stand life

item Samac, Deborah - Debby

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 11/16/2010
Publication Date: 11/16/2010
Citation: Samac, D.A. 2010. Reducing crown and root diseases of alfalfa for improved yield and stand life [abstract]. In: 2010 Minnesota Forage Research Symposium, November 17-18, 2010, St. Cloud, Minnesota. p. 26.

Interpretive Summary:

Technical Abstract: In the Upper Midwestern U.S., winter injury can reduce the density of alfalfa plants and significantly reduce yields. Although cold temperatures cause injury, diseases that affect roots and crowns increase the damage from cold temperature stresses. Brown root rot (BRR) of alfalfa, a fungal disease that reduces winter survival of alfalfa, was found for the first time in Minnesota and Wisconsin in 2003. Surveys to determine the distribution of the fungus causing the disease found the pathogen to be widespread in Minnesota and Wisconsin as well as in northeast locations such as New York, Maine, Pennsylvania, Vermont, New Hampshire, and Ontario, Canada. Disease management strategies are inherently limited for soil-borne pathogens. Overall, strategies should be focused on maintaining good plant health as the growing season draws to a close. Tests on 15 commercial varieties grown in Minnesota production fields with damaging levels of BRR indicated that adequate levels of resistance to the disease already occur in some locally-adapted varieties. Rotating with spring-sown small grain crops such as oat, barley, and wheat reduces inoculum levels, as does fallowing the field. Mycoleptodiscus crown and root rot was identified causing severe disease in seven commercial production fields in southeastern Minnesota and southwestern Wisconsin during the summer of 2009 and spring of 2010. Although the disease has been known on red clover since the 1950s, it has not previously been reported to cause severe problems in alfalfa production fields. A test was established in 2010 at the University of Minnesota Rosemount Research and Outreach Center in a field with high incidence of the disease to evaluate disease resistance and fungicide efficacy.