Postemergence Weed Control in Alfalfa May 9, 2018
Scout and, if necessary, treat new alfalfa fields for weeds before they get a foothold.
Alfalfa seedlings compete poorly with weeds and vigorous weed growth this spring might be making it extra tough for your seedlings.
When weeds, especially broadleaf weeds, threaten seedling alfalfa, one common control method is mowing. If used, adjust mowing height so several leaves remain on alfalfa seedlings after clipping to aid regrowth. Also, mow weeds before they get so tall that they produce a large quantity of clippings that could smother small seedlings.
If you would rather spray broadleaf weeds than mow them, Buctril, Butyrac, Pursuit, or Raptor are labeled. Buctril controls most small broadleaf weeds fairly inexpensively, however alfalfa injury can result if temperatures exceed 80°. If you expect high temperatures at the time of spraying, Butyrac, Pursuit, or Raptor might be preferred. These herbicides control most small broadleaf weeds, but weeds must be less than three inches tall or results will be inconsistent. Pursuit and Raptor are more expensive but their residual soil activity will continue to control weeds throughout much of the season.
Mowing is not very effective with grassy weeds. To kill grassy weeds use Poast or Select. Use the appropriate adjuvant and make sure you spray before grasses get 4 inches tall or control will be spotty.
Weeds reduce growth of new alfalfa by shading and competing for moisture. You can prevent these problems by acting quickly to scout and treat where necessary.