Growers should take a close look at alfalfa before winter to control weeds that can cause problems next spring, a University of Nebraska forage specialist said.

As long as the ground isn't froze solid, there's still time to survey fields for weeds, said Bruce Anderson, forage specialist in NU's Institute of Agriculture and Natural Resources. Growers can take action now to control mustard, pennycress, downy brome, cheatgrass or abundant yellow- or white-flowered weed problems, he said.

"These weeds are tiny right now, so you might need to look close to see them," Anderson said. "But they're in your alfalfa, and early next spring they could grow rapidly, reducing alfalfa yield, thinning stands and lowering forage quality."

Although most alfalfa stands have become dormant due to recent cold temperatures, soils haven't yet froze solid, making now the perfect time to apply herbicides, he said.

Recent rains may have made weeds more prevalent, but more susceptible to herbicides in the near future, Anderson said. Herbicides such as Karmex, Sinbar, Sencor and Velpar may be effective in controlling winter annual weeds in alfalfa stands more than a year old, he said.

"All these herbicides do a good job of controlling broadleaves like pennycress and mustard," he said. "They also do a pretty good job of controlling downy brome. Karmex is not good for downy brome, but may be the best choice for broadleaf control on low organic matter soils."

However, these herbicides should not be used on alfalfa fields seeded this year because they will injure young plants, Anderson said.

Pursuit and Raptor herbicides are best when both broadleaf and grassy weeds are a problem, he said. For grasses such as volunteer wheat, use Poast or Select. Buctril or Butyrac are good for controlling only broadleaf weeds as long as temperatures remain above freezing for a few days, he said.

"Take advantage of some opportunities in November to control weeds in your alfalfa. That way you won't be plagued by them next spring," he said.