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ARS Home » Midwest Area » St. Paul, Minnesota » Plant Science Research » Research » Publications at this Location » Publication #208947

Title: Alfalfa root health and disease management: a foundation for maximizing production potential and stand life

item Samac, Deborah - Debby

Submitted to: Forage Focus
Publication Type: Trade Journal
Publication Acceptance Date: 2/15/2007
Publication Date: 3/1/2007
Citation: Samac, D.A., Malvick, D., Hudelson, B., Gibbs, A., Hollingsworth, C. 2007. Alfalfa root health and disease management: a foundation for maximizing production potential and stand life. Forage Focus. p. 6-7.

Interpretive Summary:

Technical Abstract: Beneath the lush green leaves of an alfalfa plant is a surprisingly large root system. It is this large root system that is at the heart of the valuable traits of the crop. Many factors influence root growth and root health of alfalfa, but diseases can be especially important. Several different diseases infect the roots of alfalfa, but among those, two emerging diseases in the Upper Midwest are more damaging and widespread than was thought at one time. In the past few years, reports of problems caused by Aphanomyces root rot have become more common. At least two different races of the Aphanomyces pathogen are known that attack alfalfa; however, most alfalfa cultivars with Aphanomyces resistance only have resistance to race 1. A survey is being conducted to determine the frequency of race 2 isolates in Wisconsin and southeastern Minnesota. Preliminary results show a predominance of Aphanomyces race 2. In 2003, brown root rot of alfalfa was reported for the first time in Wisconsin and Minnesota. It is likely that the fungus causing this disease has been present for many years but was not recognized. A 3-year survey showed that the pathogen is present across Minnesota and Wisconsin and may be more common in the Red River Valley, St. Croix River Valley, and west of Green Bay. Our research shows that its inoculum increases using corn and soybean plant debris, but how this contributes to the disease is not yet known. Currently, no resistant varieties are available, although trials are in progress to determine if current cultivars have resistance to the disease.