Herbicide Resistance Management: Proactive Approaches for Long-Term Effectiveness

Herbicide resistance in weeds seems to be exploding. For example, Waterhemp populations in the Midwest are now surviving three or more herbicide modes of action, and relying on chemical control that worked five years ago may now be fueling resistance.¹ And that’s just one weed species. There are 273 species of weeds that have developed resistance to 168 different herbicides, and more are showing new resistance each year.²
However, it’s not too late to halt the spread of herbicide-resistant weeds. By taking a proactive, diversified approach to weed management, you can slow the development of resistance, preserve your herbicide efficacy and regain control over your fields. The key is to stop relying solely on herbicides and instead implement a holistic strategy that incorporates cultural, mechanical and chemical tactics.

How weeds are increasingly evolving resistance to herbicides

It’s astounding how weeds are increasingly evolving resistance to herbicides. However, the cause is clear: Repeating the same herbicide mode of action season after season accelerates the selection pressure. Surviving weeds reproduce, resistance traits increase and suddenly you’re dealing with multiple modes of action failing at once.
Left unchecked, this resistance can spread fast, something we’re already seeing across the Corn Belt.³
To combat the spread of herbicide-resistant weeds, you have to mix up your tactics. Here are a few things you can do to minimize the presence of herbicide-resistant weeds in your fields:

• Scout fields 10-14 days post-application to identify and find weeds that may be developing resistance. Once identified, remove them before they go to seed.
• Rotate your chemistry and keep track of what is working and what isn’t.
• Use other forms of control, including tillage, crop rotation and cultivation.
• Implement non-chemical methods like targeted mechanical removal to control escapes and prevent weed seed production.
• Adopt a zero tolerance policy using hand removal when practical to clean up any last escapes and prevent seed production.

Optimizing herbicide-resistant management through tank mixing and rotation

The key to effective herbicide-resistant management is to keep weeds guessing. If you rely on just one herbicide mode of action, you’re giving herbicide-resistant weeds a chance to adapt and spread. Instead, rotate between herbicide groups from season to season, or better yet, tank mix multiple modes of action in a single pass.⁴
Tank mixing is essential, but it only works when every ingredient pulls its weight. If you’re combining two products and only one controls your problem weed, you’re not managing resistance, you’re training it.
To get it right:

• Include two or more effective modes of action for each target weed.
• Always use full labeled rates. Sub-lethal doses are a fast track to failure.
• Vary your program, not just your active ingredients. Pre, post and residuals should all play a role.⁵

Always read and follow label instructions when using herbicides.

Integrating cover crops to combat herbicide-resistant weeds

Cover crops can be an instrumental tool in your arsenal to combat herbicide-resistant weeds. By selecting vigorous cover crops, you can ultimately outcompete any weeds during the cover crops’ growing season and, after termination, create a mulch layer of crop residue that suppresses them.
To maximize suppression, plant a thick stand of cover crops and use aggressive species, such as cereal rye, in both soybeans and corn.
However, you need to be careful with the timing of planting and termination to optimize the use of your cover crops. Also, be on the lookout for inconsistent seedbed conditions, nitrogen tie-up or allelopathic effects of the cover crop if not managed properly.⁶

Adopting longer crop rotations

Short crop rotations, especially if it’s continuous corn or soybeans, can create the perfect conditions for herbicide-resistant weeds to develop. Two-year rotations are no longer cutting it for resistance management.
Longer rotations provide you with more tools to use, including various herbicides, different planting windows and new canopy structures. Adding a small grain, forage crop or cover crop provides more flexibility and opportunities to manage weeds before they spread.
Throwing a curveball at weeds will prevent them from establishing a seed bank full of herbicide-resistant traits in your fields.
If you’re still using the same program from five years ago, it’s time to rethink your strategy. An integrated weed management approach can help you layer multiple tools to outsmart weeds before they outsmart you.
Experts are available to help you make your weed management decisions. Reach out to your seed retailer, a nearby extension office agent or a seed company professional like your regional BASF representative.

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Endnotes

1. Anderson, Meaghan, and Micheal D. K. Owen. “Suspected 2,4‑D Resistant Waterhemp Population Discovered.” Crop News: Integrated Crop Management, Iowa State University Extension and Outreach, 13 Feb. 2024, crops.extension.iastate.edu/cropnews/2024/02/suspected-24‑d‑resistant‑waterhemp‑population‑discovered.
2. Ganie, Zahoor, and Amit Jhala. “Multiple Herbicide‑Resistant Weeds and Challenges Ahead.” CropWatch, Institute of Agriculture and Natural Resources, University of Nebraska–Lincoln, n.d., cropwatch.unl.edu/multiple‑herbicide‑resistant‑weeds‑and‑challenges‑ahead.
3. Ganie and Jhala. “Multiple Herbicide‑Resistant Weeds and Challenges Ahead.”
4. Unglesbee, Emily. “Tank Mixing or Herbicide Rotation: Which Strategy Is Best?” Grow IWM, Integrated Weed Management Innovations, 29 Oct. 2024, growiwm.org/tank-mixing-or-herbicide-rotation-which-strategy-is-best.
5. Unglesbee. “Tank Mixing or Herbicide Rotation: Which Strategy Is Best?”
6. Brhel, Jenny, Chris Proctor, Katja Koehler‑Cole, and Amit Jhala. “Cover Crop Termination Tradeoffs.” CropWatch, Institute of Agriculture and Natural Resources, University of Nebraska–Lincoln, 8 Apr. 2021 (updated 9 Apr. 2025), cropwatch.unl.edu/2021/cover‑crop‑termination‑tradeoffs.