March 1, 2012

In alfalfa early March is a good time to initiate spring weed control measures.

Weeds like pennycress, downy brome, mustards, cheatgrass, and shepherd's purse are common in first cut alfalfa. They lower yields, reduce quality, lessen palatability, and slow hay drydown. If you walk over your fields during the next few weeks, you’ll see their small, green, over-wintering growth.

Once alfalfa starts growing, you can't control these weeds well without hurting your alfalfa. However, if you treat your alfalfa as soon as the weather allows, you can have cleaner, healthier alfalfa at first cutting. Several herbicides can help control winter annual grasses and weeds in alfalfa, including Sencor, Velpar, Sinbar, Pursuit, Raptor, Karmex, Roundup, and Gramoxone. They all control mustards and pennycress, but Karmex and Pursuit do not control downy brome very well.

If you delay treatment until alfalfa shoots are green, your alfalfa growth might be set back a couple weeks. With a late treatment, use Pursuit or Raptor because they tend to cause less injury to your alfalfa.

Bruce Anderson
Extension Forage Specialist