Postemergence Weed Control in Alfalfa

Postemergence Weed Control in Alfalfa May 4, 2016

With all the recent moisture, alfalfa is growing well — as are broadleaf and grassy weeds in the alfalfa.

Alfalfa seedlings compete poorly with weeds, especially given weeds may have gotten a vigorous start this spring.

When weeds, especially broadleaf weeds, threaten seedling alfalfa, mowing is often used to control them. Adjust mowing height so several leaves remain on the alfalfa seedlings after clipping so plants can regrow rapidly and mow before the weeds are so tall they produce a large quantity of clippings that might smother the young alfalfa seedlings.

If you would rather spray broadleaf weeds, Buctril, Butyrac, Pursuit, or Raptor should provide control.  Buctril controls most small broadleaf weeds, but alfalfa injury can occur when temperatures exceed 80°F.  If you expect such temperatures when you spray, it might be better to use Butyrac, Pursuit, or Raptor.  These herbicides also control most small broadleaf weeds less than three inches tall; results will be inconsistent with larger weeds.  Pursuit and Raptor are more expensive but their soil activity will continue to control weeds throughout much of the season.

With grassy weeds mowing is not very effective; Poast Plus or Select should provide the control needed. Be sure to spray before grasses are 4 inches tall or control will be spotty.

Weeds reduce growth of new alfalfa by shading and competing for moisture; however, if you act quickly, you can prevent these problems. Exam your fields soon and control weeds as needed.