Keep stands thick and vigorous, harvest at the right time and utilize carefully selected herbicides. Those are your best bets for reducing foxtails and other weedy grasses in alfalfa, says Bruce Anderson, forage specialist with University of Nebraska Extension.
Thick and thrifty stands of alfalfa compete aggressively with invading foxtail, notes Anderson. “In addition, 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.”
Unfortunately, harvesting after bloom begins is easier said than done and sacrifices some forage quality.
Herbicides are another option. Roundup works great, but only for Roundup Ready varieties, Anderson says. In conventional alfalfa, Select Max and Poast Plus work well on seedling, annual grasses less than 4” inches tall. Alfalfa tolerates both herbicides very well.
Gramoxone Extra is a “more risky option,” says Anderson. “Gramoxone burns back top growth of all green plant material. This will kill most annuals like foxtail, but it also can injure alfalfa regrowth.” He advises only using it immediately after harvest and before any new regrowth appears.
None of these herbicides have soil residual activity, so good plant coverage is necessary. “You may need to repeat the spraying if new weeds emerge.”