May 7, 2010

Vigorous weed growth this spring may be making it extra tough for alfalfa seedlings to compete.

When weeds, especially broadleaf weeds, threaten seedling alfalfa, mowing is often used for control. Adjust mowing height so several leaves remain on alfalfa seedlings after clipping so your alfalfa seedlings regrow rapidly. Also, mow weeds before they get so tall that they produce a large quantity of clippings that might smother the alfalfa.

If you would rather spray broadleaf weeds than mow them, use Buctril, Butyrac, Pursuit, or Raptor. Buctril controls most small broadleaf weeds, but alfalfa injury can occur when temperatures exceed 80 F. If you expect those high temperatures when you spray, it might be better to use Butyrac, Pursuit, or Raptor. These herbicides 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.

Mowing is not very effective with grassy weeds, so use Poast Plus or Select to kill grassy weeds. Make sure you spray before grasses are 4 inches tall or control will be spotty.

Weeds reduce growth of new alfalfa by shading and competing for moisture so act quickly when weeds develop to prevent these problems.

Bruce Anderson
Extension Forage Specialist