April 17, 2013

Weeds can be a major problem in spring-seeded alfalfa. Roundup Ready® alfalfa varieties can help overcome these weeds, but Roundup® isn’t the only good herbicide option for alfalfa.

Alfalfa seedlings grow slowly, while many competing weeds grow faster. This can rob seedlings of moisture, nutrients, and light and, when weeds are left uncontrolled, cause thin stands, weak plants, and lower yields in alfalfa.

Cropping practices that reduce weed seed production in years prior to alfalfa help reduce weeds when you finally do plant alfalfa. Timely mowing reduces competition from many weeds, but often herbicides are the only method to fully control weeds.

If you expect grasses like foxtail or crabgrass to be a problem in your new alfalfa, before seeding use a pre-plant incorporated herbicide like trifluralin, Balan, or Eptam. These herbicides control grasses and many small-seeded broadleaf weeds like lambsquarter and kochia. Some larger-seeded broadleaves like velvetleaf and sunflower will not be controlled, but you can mow those weeds later for good control.

For weed escapes, consider a postemergence herbicide like Buctril and 2,4-DB to control broadleaves, Poast Plus and Select to control grasses, and Raptor or Pursuit to control a combination of weeds. They can rescue your alfalfa as long as weeds are sprayed before they get very tall.

As with all pesticide applications, read and follow label directions for rates and conditions.

Bruce Anderson
Extension Forage Specialist