|Hollingsworth, Charla -|
Submitted to: Extension Publications
Publication Type: Other
Publication Acceptance Date: May 25, 2009
Publication Date: May 30, 2009
Citation: Hollingsworth, C., Samac, D.A. 2009. Reducing Alfalfa Brown Root Rot with Crop Rotation. University of Minnesota Extension Forage Program. Forage Quarterly. 3(2):2. Technical Abstract: Stand injury resulting from brown root rot (BRR) of alfalfa, caused by Phoma sclerotioides, may be noted this spring as warmer temperatures promote stand emergence. BRR development occurs primarily over the winter and is favored when stands are covered with snow for an extended period of time. It is at this time of year when dark-colored root lesions on susceptible plants become established or increase in severity. In the spring, diseased plants are often slower to green up than their healthy counterparts and may be comparatively less thrifty throughout the summer. Severely diseased plants die during the winter. Options for disease management are limited because it cannot be controlled with seed treatments. There are no known BRR-resistant alfalfa varieties adapted to our production environment although field tests to identify resistant varieties are in progress. Crop rotation is our most effective management strategy at this time. This fungus is a well-adapted saprophyte that can survive on a large number of hosts. Previous disease management recommendations of planting spring-sown small grain crops in rotation with alfalfa are supported by recent research measuring colonization of the fungus on crop residue. For fields with high populations of P. sclerotioides, rotating into corn and soybean is not recommended, as it may not reduce inoculum levels between alfalfa crops.