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United States Department of Agriculture

Agricultural Research Service

Title: Brown Root Rot of Alfalfa: What's the Big Deal?

Authors
item Peterson, Paul - UNIVERSITY OF MINNESOTA
item Samac, Deborah
item Hollingsworth, Charla - UNIVERSITY OF MINNESOTA

Submitted to: Minnesota Forage and Grassland Council Forage Connection Newsletter
Publication Type: Abstract Only
Publication Acceptance Date: November 1, 2003
Publication Date: December 1, 2003
Citation: Peterson, P., Samac, D.A., Hollingsworth, C. 2003. Brown root rot of alfalfa: what's the big deal? Minnesota Forage and Grassland Council Forage Connection Newsletter. p. 7.

Technical Abstract: Brown root rot (BRR) is a fungal disease (caused by Phoma sclerotioides) associated with stand decline and reduced yield of forage legumes. The first report of BRR in North America was on sweet clover in Canada in the 1930s. The pathogen was found widespread in Alberta's Peace River Valley in the 1980s. The first BRR report in the continental U.S. was only recently, 1996, in Wyoming. It was reported in Montana the same year and confirmed in Idaho 5 years later. Since spring 2003, Wisconsin, New York, and Minnesota have confirmed the presence of the fungus from diseased alfalfa plants. It is possible that this cold-loving fungus has been present in the north central U.S. for many years. It may have contributed to alfalfa stand decline in the past but was not identified. Symptoms of BRR include dark lesions or rot on tap and lateral roots as well as nodules. Interference with carbohydrate storage and/or rotting of the storage area of the upper taproot and lower crown increase susceptibility of plants to winter kill. A recently developed molecular test allows researchers to determine in a few hours whether the fungus is present in plant tissues. Alfalfa plant samples from fields in seven MN counties (Marshall, Pennington, Red Lake, Washington, Dakota, Wabasha, and Steele) have been tested. So far, the pathogen has been found in all three northwestern MN counties tested.

Last Modified: 10/22/2014
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