Treating weeds as soon as the weather allows improves the odds of a cleaner, healthier alfalfa stand at first cutting, says Bruce Anderson, forage specialist with University of Nebraska Extension.
“Weeds like pennycress, downy brome, mustards, cheatgrass and shepherd's purse are common in first-cut alfalfa,” he says. “They lower yields, reduce quality, lessen palatability and slow hay drydown.”
The herbicides Sencor, Velpar, Sinbar, Pursuit, Raptor, Karmex, Roundup and Gramoxone all control mustards and pennycress, Anderson says. “But Karmex and Pursuit do not control downy brome very well. To be most successful, you must apply most of these herbicides before alfalfa shoots green up this spring to avoid much injury to your alfalfa. During mild winter weather would be a great time.
“If you wait and alfalfa shoots are green when you spray, your alfalfa growth might be set back a couple weeks. If it does get late, use either Pursuit or Raptor because they tend to cause less injury to your alfalfa.”