Controlling Summer Grasses In Alfalfa

Controlling Summer Grasses In Alfalfa

June 26, 2009

Wet soils in alfalfa fields right after cutting will certainly do one thing: Help weedy grasses like foxtail grow. To manage these weeds in your hay:
  • Keep your alfalfa thick and thrifty so it will compete aggressively with invading foxtail. Thick initial stands and good soil fertility are needed.

     

  • Harvest alfalfa only after it begins to bloom or when new shoots appear at the base of the plants. Then alfalfa should regrow rapidly so foxtail doesn't get much time to become a problem. This method may be easier said than done and will sacrifice some forage quality since harvest occurs after bloom begins.

     

  • Apply herbicides. Roundup® works great for Roundup Ready® varieties. In regular alfalfa, Select Max® and Poast Plus® control annual grasses. These herbicides work well on seedling grasses that are less than 4 inches tall, and alfalfa tolerates both herbicides very well. Gramoxone Extra® is a more risky herbicide. Gramoxone burns back top growth of all green plant material. This will kill most annuals like foxtail, but it also can injure alfalfa regrowth that has already emerged. Only use Gramoxone immediately after harvest and before new regrowth shoots appear.

    None of these herbicides has any soil residual activity, so good plant coverage is necessary and you may need to repeat the spraying if new weeds emerge.

If weedy grasses are a problem in your hay, thick and vigorous alfalfa stands and some well-chosen herbicides can help you get it under control.

Bruce Anderson
Extension Forage Specialist