Fall Applications Benefit Spring Weed Control
Post-harvest is a prime time to begin building next year’s weed control program, especially if resistant weeds, including kochia and Palmer amaranth, are an issue.
Weed management becomes more complicated as weeds like kochia evolve resistance to herbicides. In fact, a Colorado State University study published in September 2025 documented glyphosate-resistant kochia in 10 states, noting that resistant weed seed may be spreading via farm equipment and birds, as well as natural selection for new resistant biotypes.
The study, published in Weed Science, notes management strategies that prevent seed production and minimize pollen escape from resistant weed populations.
Weeds that are controlled before they reach maturity or are not allowed to emerge are prevented from producing seed, helping minimize resistance development.
Other resistance management strategies recommended include using preemergence soil-residual herbicides, rotating modes of action, rotating crops, narrow-row planting systems, and cover crop adoption.
The study’s authors say, “Reliance on postemergence glyphosate alone is no longer viable. Therefore, integrating herbicides with different modes of action, especially preemergence herbicides with good residual activities, and crop rotation may prevent seed deposition and infestation of GR B. scoparia in soil.”
Getting a jump start on controlling resistant weeds, then, often requires a weed control plan that begins soon after harvest and continues for months before loading planters.
Fall-Applied Herbicides Benefits
Fall-applied herbicides offer several benefits, including long-lasting residual weed control and improved planting date flexibility next spring.
Will Griffin, row crop segment manager with Valent U.S.A., recommends growers begin 2026 weed control with a fall burndown herbicide tank mix that includes either Fierce® EZ Herbicide or Fierce® MTZ Herbicide.
“The intent is to control those weeds before they emerge, giving you the opportunity to plant into a clean seedbed. And then, depending on your cropping system, come back early in the season with overlapping preemergent and postemergent residual activity to control weeds through canopy closure,” says Griffin.
Realizing the Benefits
In addition to benefiting spring weed control, fall-applied herbicides can enable an earlier spring start, offer flexibility in planting timing, and enhance management of resistant weeds.
With weed resistance a growing problem across all U.S. corn and soybean-producing regions, growers are searching for herbicide options that provide longer control of resistant populations, especially in areas with a high rate of preventative planting.
“Our take-home message is to act now to control weeds while you can.“
Will Griffin, Row Crop Segment Manager, Valent U.S.A.
Identifying Ideal Conditions
Fall burndown treatments, using products such as Fierce EZ or Fierce MTZ herbicides, with residual activity, help minimize perennial weed pressure coming out of the winter months.
“Our take-home message is to act now to control weeds while you can,” Griffin says. “In the Midwest, the earlier you can get a post-harvest herbicide application out, the better. Then, as you get into the spring season, having that clean seedbed provides a larger window of opportunity for planting, and you’re not losing nutrients to weeds.”
In some southern growing regions, post-harvest herbicide timing is more flexible.
“A fall burndown will reduce the time it’s going to take to get back in and plant because you’re not waiting for your preplant burndown to work on those big weeds. Instead, you’re able to control weeds with a simple one-pass program, so you can jump in and start planting,” Griffin says.
Fall herbicide applications also ensure moisture is available for activation. “While we don’t always know when it’s going to rain, we always know we’re going to get rain when the snow melts,” Griffin says.
Why Fierce EZ or Fierce MTZ Herbicides?
Tank mixing Fierce EZ or MTZ herbicides with standard fall burndown applications ensures up to 8 weeks of residual control of resistant small-seeded broadleaves and grasses, including winter annual weeds and early emerging summer annuals such as kochia and common lambsquarters.
“Tank mixing Fierce EZ or MTZ herbicides with standard fall burndown applications ensures up to 8 weeks of residual control.”
Will Griffin, Row Crop Segment Manager, Valent U.S.A.
“If you’re going out with a fall burndown, putting out a residual makes sense because you’ve already spent the money to go across the field. You’re ensuring weeds stay controlled through the winter and into the early spring, controlling small, actively growing weeds before they can compete with your corn or soybean crop,” Griffin says.
Fierce MTZ contains three effective modes of action to deliver up to eight weeks of broad-spectrum control, outlasting the germination period of tough, resistant small-seeded broadleaves and grasses.
Fierce EZ contains two effective modes to deliver up to eight weeks of broad-spectrum control, outlasting the germination period of tough, resistant small-seeded broadleaves and grasses.
For more information about fall-applied burndown applications, visit Valent.com or contact your local Valent representative.