Postemergence Weed Control In Alfalfa

Postemergence Weed Control In Alfalfa

June 19, 2009

When weeds threaten seedling alfalfa, control them with mowing or a herbicide application, basing your choice on weed type and size.

Mowing is a common control method, especially with broadleaf weeds. When mowing, be sure to leave several leaves on the plant so seedlings will regrow rapidly. Also, mow before plants are so large that their clippings could smother small seedlings.

Applying Herbicide. If you want to spray broadleaf weeds, use Buctril, Butyrac, Raptor, or Pursuit. Buctril controls most small broadleaf weeds, but can injure alfalfa when temperatures exceed 80°F. Since these temperatures are typical now, it might be better to use Raptor or Pursuit. These herbicides control most small broadleaf weeds; results will be inconsistent with weeds taller than 3 inches. Raptor and Pursuit also have soil activity that will continue to control weeds through the season. If weeds are much taller than 3 inches, mowing or haying may be as good or better over all.

With grass weeds, mowing is not very effective so use Poast or Select. Make sure you spray before grasses are 4 inches tall or control will be spotty.

Weeds slow the growth of new alfalfa by shading and competing for moisture. You can prevent these problems by scouting now and acting quickly to control problem weeds.

Bruce Anderson
Extension Forage Specialist