Record winter high temperatures are causing earlier weed emergence, so now is the time to control winter annual weeds in alfalfa.
Thin field stands, combined with open soil surfaces and adequate moisture, can result in high weed pressure. Prior to alfalfa shoot green-up, or dormancy break, scout fields for early green winter annual weed patches of pennycress, downy brome, mustards, cheatgrass and shepherd’s purse. Left unchecked, these weeds can lower first-cutting hay yield, quality and palatability. Excessive weeds also can extend dry-down and lengthen harvest time.
Before applying any herbicide, scout current and potential weed pressure. Verify fields have enough weeds to justify herbicide applications, then determine the best management options.
Winter annual weeds can grow better during cooler spring temperatures than alfalfa, so dormant alfalfa herbicides such as MCPA Amine, metribuzin and Gramoxone can still be applied. Pre-emergent herbicides such as Warrant, Chateau and Prowl H2O can be applied soon after green-up, but these chemicals will not control weeds that have already germinated.
Aim herbicide will control early-growing broadleaf weeds but not grassy weeds. Poast herbicide will control most growing weedy grasses, but not downy brome. Pursuit and Raptor herbicides control growing henbit well during early alfalfa green-up, but control weeds best when air temperatures are warmer. Glyphosate products such as Roundup Weathermax and Powermax will control growing weeds with warmer temperatures; however, they must be used with Roundup-tolerant alfalfa varieties.
Other alfalfa field products include Balan, Trust, Moxy, Arrow, Select Max, Velpar, Karmex, Sinbar, Pursuit, Butyrac and Raptor. The University of Nebraska-Lincoln Extension publication EC 130, “Guide for Weed, Disease, and Insect Management in Nebraska,” provides additional information.
Winter annuals can quickly establish in hay fields, so early-season weed control is important for quality hay production. Timing is essential, so control winter annuals before alfalfa breaks dormancy and before weeds cause economic losses. For more alfalfa information, visit https://cropwatch.unl.edu.
Todd Whitney is a University of Nebraska-Lincoln irrigation and cropping systems Extension educator based in North Platte.
PHOTO: In the spring field young alfalfa grows. (Adobe Stock │ #261830518 – orestligetka)
