Wisconsin

In establishing alfalfa, pigweed and lambsquarter can be significant problems, says Dan Undersander, University of Wisconsin extension forage specialist. Use Pursuit or Raptor after seeding. The weeds are problems only within 60 days of seeding, can reduce alfalfa stand and yield and increase fiber of harvested forage.

Southeast

Kentucky

For fall-seeded alfalfa, winter-annual weeds such as common chickweed and purple deadnettle are trouble, generally in late winter and early spring and only at first cutting. Common chickweed challenges first-crop cutting and curing, reducing quality. Winter-annual weeds are less of a problem in well-established, thick stands.

Summer-annual crabgrass and common ragweed can hurt spring-seeded alfalfa. Herbicide options are often limited; much of Kentucky's alfalfa is seeded with grasses such as orchardgrass. For new, pure alfalfa seedings, use Pursuit or Raptor, says J.D. Green, extension weed scientist, University of Kentucky. For weedy grasses, selective postemergent herbicides include Select, Poast or other products.

Curly dock is problematic in Kentucky; no herbicides can effectively control it, says Green. It persists throughout the growing season, but is more evident during first cutting, since it produces seed heads in spring. A perennial dicot, curly dock can reduce alfalfa hay quality and yield. Don't plant alfalfa in fields with curly dock present; control the weed in previous crops.

Tennessee

Crabgrass decreases yield and quality in spring seedings. Control with Select or Poast Plus in late April and into May, says Gary Bates, forage specialist, University of Tennessee.

In established alfalfa, Tennessee growers fight pigweed, johnsongrass and curly dock, which drop yield and quality in mid- to late season. Johnsongrass can be handled with Select; Pigweed with Pursuit or Butyrac. Make sure curly dock is out of fields before planting alfalfa.

Northeast

Connecticut

Most weed prevention is done before seeding, because growers here plant few pure alfalfa stands, says Richard Meinert, cooperative extension educator, University of Connecticut.

Several Roundup applications kill or reduce weed seeds; then alfalfa and grass are seeded. For pure stands, small grain cover crops are used the first year to substitute for grass and suppress weeds.

Delaware

Most alfalfa here is fall-established, so winter annuals such as henbit, chickweed, shepherdspurse, speedwell species, mustard species, etc., are problems, says Quintin Johnson, crop specialist with the University of Delaware. These weeds are most competitive in the fall and early spring and can affect first-cutting forage quality. Dependent upon species, dormant applications of Gramoxone, Pursuit or Raptor or postemergent sprays of 2,4-DB, Pursuit or Raptor are good control options.

In established conventional alfalfa, horsenettle is a big problem followed by biennial thistles and Canada thistle; all more so after first cutting. Horsenettle and Canada thistle can be controlled with good cultural practices and glyphosate spot-sprays. Biennial thistles are controlled with 2,4-DB or suppressed with dormant or post-cutting Raptor applications. Forage palatability and hay quality are reduced and severe infestations affect yields. Horsenettle berries can also be poisonous to livestock.

Maryland

With late-winter alfalfa seedings, problem weeds tend to be lambsquarter and pigweed early and crabgrass, foxtail and fall panicum in mid- and late summer. With late-summer seedings, winter annuals chickweed and henbit are problems, says Les Vough, University of Maryland extension forage specialist emeritus. Spray depending on the severity of the problem and amount of competition. The weeds generally reduce quality and can reduce alfalfa stands.