Dormant Alfalfa Weed Control

While the amount of snow we’ve had to push so far this winter has been minimal, an open winter does have some consequences for our perennial forage crops like alfalfa.  Without a protective blanket of snow, the risk of winterkill in a stand is increased. In some cases added on top of this was a late fall cutting that stressed the stand even further.   This leaves us with a stand that will be slower to green up and fill in with the possibility of larger open areas from winterkill.  This is the perfect opportunity for winter annual weeds to rear their ugly heads.

Plants like henbit, pennycress, shepherd’s purse, mustard, annual bluegrass, and cheatgrass seem to magically appear in our stands every spring.  These winter annuals germinate in the fall, lie dormant during winter, then pick up growth quickly in the spring as warm temperatures return.  Greening up before almost any other plants in our fields gives these species a competitive advantage, and they capitalize on it with fast growth and quick maturity, often setting seed before other summer annuals have done much more than starting to grow.

This speedy life cycle means our window for control is limited, especially in alfalfa.  Because we don’t want to damage our alfalfa plant during the fall as it prepares for winter, or later in the spring as it starts new growth, the best window of opportunity is in the short time during spring where winter annuals have started to grow again, but alfalfa is still dormant.

To take advantage we need to be ready to act.  Scout alfalfa fields and determine where weed issues may arise, then keep an eye on these spots as we get closer to spring.  Weeds can reduce overall yield, lower hay quality and palatability, and slow dry-down time for the first cutting. Producers whose goal is dairy quality hay will most likely find the benefit of control worth the expense.  If the hay is destined for dry cows in a beef herd, the difference between benefit and cost may need a closer examination.

It is also important to identify what species need to be addressed.  Herbicide efficacy varies by species, so picking the product that best controls your problem weed can prevent future applications and save money in the long run.  Need for broadleaf or grass weed control is especially important to identify as some broadleaf products have no action at all on grasses.

Producers with RoundUp-Ready alfalfa varieties can apply glyphosate at almost any time without the worry of damaging their crop.  However, best control will occur when weeds are small and by treating early, you can count on a cleaner harvest at first-cutting.

Stress from fall cuttings and a low snow winter have left many alfalfa fields susceptible to a winter annual invasion this spring.  To prevent this, we need to be ready to act when the short window of opportunity presents itself, when weeds have started growth but alfalfa plants have not.  Scout early and often to know exactly when to pull the trigger, as well as being able to select an herbicide that addresses the weeds you are facing.  If you need help selecting the right product for your situation, your local extension office will be happy to connect you with an educator that can provide guidance.

-Ben Beckman is a beef systems Extension Educator serving the counties of Antelope, Cedar, Knox, Madison and Pierce.  He is based out of the Cedar County Extension office in Hartington.  You can reach him by phone: (402) 254-6821 or email: .