Extension Ag Update
November/December 2003
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Winter Annual Control in Established Alfalfa

Ellen Phillips, Crop System Extension Educator, Countryside Extension Center, 708-352-0109, ephillps@uiuc.edu

Henbit, shepherd’s purse, mustard, chickweed and downy brome may be lurking in your alfalfa field as young seedlings. If allowed to over winter, they will grow quickly in the spring, thinning alfalfa stands and reducing the yield. Winter annuals in alfalfa stands more than a year old can be controlled once the alfalfa goes dormant.

Scout in the fall for winter annual seedlings such as mustard, annual bluegrass and downy brome.  To learn what these and other winter annuals look like in the seedling stage, check out the University of Illinois Weed Identification website at http://web.aces.uiuc.edu/weedid/

Once alfalfa is dormant following a freeze but where the soils have not frozen, there are several herbicides you can chose from to control these weeds.  Choosing the correct herbicide is important.  The Weed Control for Small Grains chapter in the Illinois Pest Management Handbook provides a guideline on which herbicides are most effective at controlling these winter annuals.  http://www.ipm.uiuc.edu/pubs/iapmh/03chapter.pdf   Double check the herbicide label for temperature ranges for their use.  Controlling winter annuals in the fall will give you a jump on the spring activities.