Frost Injury in Alfalfa
Alfalfa is a perennial crop that produces forage for multiple seasons, regrowing each year from established crowns after winter. Alfalfa is naturally resistant to cold temperatures, with some varieties more resistant than others. Cold temperatures can be especially injurious to new spring growth.
Symptoms include discolored foliage and wilting, twisting, and death of tissue. Upper stems are more susceptible to frost injury than lower portions. Depending on the frost severity, injury can range from leaf damage at the stem tops to complete stem death resulting in lower yields or a delayed first cutting date. Plants are more resistant to cold temperatures as the season progresses. Frost injury during the fall can prevent adequate movement of carbohydrates to below ground plant tissue, and winter hardiness can be reduced. Systemic disease increases frost susceptibility in alfalfa plants, and frost injury increases plant susceptibility to alfalfa diseases. Bacterial stem blight is often associated with frost damage of alfalfa.
Dead alfalfa stems caused by frost.
Deborah Samac
Symptoms of frost injury on alfalfa.
Deborah Samac
Letting plants regrow after a mild to moderate frost is often the most reasonable action. Check with state extension agents or extension resources to determine proper recommendations for management of severely frost-injured alfalfa.
Prepared by the Alfalfa Pest Management Working Group.
Dead alfalfa stems caused by frost. Debora Samac.
Frost on alfalfa. Deborah Samac.
Frost injury on alfalfa. Deborah Samac.
Snow on alfalfa. Howard F. Schwartz, Colorado State University, Bugwood.org.
Snow on alfalfa. Howard F. Schwartz, Colorado State University, Bugwood.org.
Gallery images courtesy Deborah Samac and Howard F. Schwartz, Colorado State University, Bugwood.org.
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