Dormant Spray For Alfalfa Weeds

Dormant Spray For Alfalfa Weeds

March 4, 2016

 With warmer temperatures and alfalfa green-up approaching, this is a great time for weed control.

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. In the next few weeks when you can walk through your fields, you should be able to see their small, green, over-wintering growth.

If your alfalfa variety is Roundup Ready, you can spray almost anytime without hurting your alfalfa.  Once conventional alfalfa starts growing, it's difficult to control these weeds without hurting your alfalfa.  However, if you treat your alfalfa as soon as possible during this spring-like weather, you can have cleaner, healthier alfalfa at first cutting.

Before spraying, be sure the weeds are causing economic damage to your alfalfa.  Spraying will give you more pure alfalfa, but may cost some in total tonnage.

Several herbicides can help control winter annual grasses and weeds in conventional alfalfa.  They include metribuzin, Velpar, Sinbar, Pursuit, Raptor, and Karmex.  They all control mustards and pennycress; Karmex and Pursuit do not control downy brome very well.

To be most successful, apply most of these herbicides before alfalfa shoots green-up this spring to avoid alfalfa injury. If alfalfa shoots are green when you spray, growth may be set back a couple weeks.  If it does get late, consider using Raptor or Pursuit because they tend to cause less injury to your alfalfa.

Timing is crucial when controlling winter annual weeds in alfalfa.  Get ready now and in the next couple of weeks take advantage of the good weather.

Bruce Anderson
Extension Forage Specialist