Brown Root Rot & Alfalfa


Brown root rot of your home garden alfalfa plants has the power to destroy them, causing visual devastation to your gardening space as well as significant crop loss. To prevent infection and plant death, and to handle a problem when it arises, become familiar with symptoms to look for as well as effective management methods.


As a preventive measure to avoid and prepare your plant to handle the brown root rot fungal infection, maintain vigorous plants. Healthy alfalfa has a higher chance of recuperating compared to a stressed or injured plant. Grow alfalfa in well-drained soil with good fertility. Maintain a salt pH of 6.0 to 6.5, according to the University of Missouri Extension. To improve drainage if your site has problems, add a grass mulch for extra protection.


Brown root rot in alfalfa is caused by the fungus Phoma sclerotioides. This soil-borne fungal pathogen remains inactive during warmer temperatures during summer, but as the temperature drops into the fall, the pathogens begin to thrive, according to the University of Minnesota Extension. Pathogens are spread sporadically and fungi germinate once in proximity to the roots of a host plant, particularly during temperatures within the range of 35 to 40 degrees F.


Brown root rot in alfalfa leads to roots that become dark and possibly covered in lesions or areas of dead tissue. Above-ground symptoms include alfalfa that has a slowed or stunted development of its green hue during the spring season as well as plants that die in winter. Small black fruiting bodies, or fungal growths, often appear on roots, and the entire plant may suffer diminished health, severe decline, stunted growth or death, according to the University of Wyoming.


Contact your local county extension agent to determine whether a resistant variety of alfalfa exists in your region; the variety Peace has shown resistance in Canada to brown root rot, according to the University of Wyoming. Commercial varieties like Cal/West 'Velvet' are also available. Keep your plant well-nourished and rich in the nutrients it needs, like sulfur and phosphorus, with an appropriate fertilizer.


Though fungicides do not offer effective control for brown root rot on alfalfa plants, natural control measures are helpful. Maintain healthy roots and well-drained soil at all times as mildly affected roots do not mean certain death. Do not cut your alfalfa plants from August through autumn, to prevent invasion of pathogens. Rotate alfalfa out of the field every three years along with other legume crops and corn, according to the University of Minnesota.

Keywords: brown root rot, alfalfa root rot, alfalfa rot control

About this Author

Tarah Damask's writing career, beginning in 2003, includes experience as a fashion writer/editor for Neiman Marcus, short fiction publications in "North Texas Review," a self-published novel, band biographies, charter school curriculum, and articles for eHow. She has a love for words and is an avid observer. Damask holds a Master of Arts in English and creative writing from the University of North Texas.