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Treat winter annuals in alfalfa

Bruce Anderson Published on 01 November 2010

With good fall conditions winter annual weeds like pennycress, mustards, henbit, and downy brome are getting a dense, robust start that could lead to heavy weed growth next spring.

Use this post-harvest period to check your fields for small henbit plants, mustard rosettes, or short grass seedlings of downy brome. If left uncontrolled, they can grow rapidly, reducing alfalfa yield, thinning stands, and lowering forage quality.

To avoid problems next spring, spray fields now before soils freeze. Herbicides that would do a good job include Sencor, Sinbar, and Velpar. All three do an excellent job of controlling pennycress, mustards, and downy brome. Raptor might be a better choice, though, if henbit is your biggest problem.

Spring treatment is also an option; however, you’ll need to spray before alfalfa greens up or you will injure your plants. Usually, there are only a few days in spring where alfalfa is dormant, weeds are actively growing, and it’s not too wet or windy. Often, fields don’t get sprayed at all or they get sprayed late and alfalfa suffers some setback.

Taking advantage of good conditions this fall to treat these winter annuals can help ensure fewer weeds and a better alfalfa stand next spring.

—Bruce Anderson, 
Extension Forage Specialist, University of Nebraska