Let’s face it, herbicide resistance sucks. It sucks nutrients, time and money from farmers. While there is no silver bullet to stopping resistance from spreading, we can take actions to slow the development of resistance and preserve the effective lifespan of herbicides.
Canada continues to rank third globally when it comes to cases of herbicide resistance (n=56), behind Australia (n=91) and the United States (n=132), according to weedscience.org.
Unfortunately, many producers across the prairies are familiar with the challenges that resistant weeds like kochia and wild oats bring to their farms.
Knowledge is power. Now that we better understand how resistance develops, it’s time to act. Resistance management starts with planning.
Planning Ahead for Effective Resistance Management
Planning crop rotations is nothing new, but how many people are planning their herbicide programs three, four or five years out? Using herbicides with multiple modes of action and rotating effective modes of action on target weeds is key to helping slow resistance development.
Weeds are smart, and they thrive on routine, so try to do something different every year to throw them off their game. Consider altering herbicide application timings like a pre-seed burndown, soil residual or post-harvest burndown or include an application timing you haven’t before. Fall and spring applied soil active herbicides are gaining in popularity in Canada, and they make an excellent addition to a resistance management strategy.
The Role of Soil-Active Residual Herbicides
Apply a soil active residual herbicide like Valtera® EZ (flumioxazin) or Astir® (sulfentrazone) to manage broadleaf weeds like kochia, chickweed, lamb’s-quarters, wild buckwheat, pigweed and many more. Fierce® EZ features flumioxazin (Group 14) and pyroxasulfone (Group 15) to manage both broadleaf and grass weeds like green foxtail and wild oats (suppression).
For those using wheat herbicides in Canada, soil residual products provide up to eight weeks of weed control after activation. They can help improve the performance of pre-seed burndown and in-crop herbicides by reducing early weed populations and flushes so weeds are smaller at pre-see burndown and/or in-crop herbicide timing. These products give crops a head start in spring and reduce the burden on post-emergent herbicides.
Nufarm’s Pre-Seed Burndown Portfolio
Nufarm offers a leading portfolio of pre-seed burndown products in Western Canada, tailored to the needs of all major crops:
- CONQUER® II – for canola
- GoldWing® – for pulses
- ThunderHawk® – for cereals
- BlackHawk® EVO – Nufarm’s latest innovation for cereals
BlackHawk EVO features Duplosan™ technology to tackle the most difficult broadleaf weeds, including Group 2- and 9-resistant cleavers and kochia. Nufarm’s pre-seed burndown products bring performance, convenience and resistance management together one robust pre-seed portfolio.
For many farms, pre-seed burndown is the first herbicide application of the season. Using multiple effective modes of action is essential, especially as resistance spreads. Understand what’s happening in your field and tailor your tank-mix accordingly.
Pairing a pre-seed burndown with a residual herbicide allows you to start clean and stay clean. This reduces weed competition, conserves soil moisture and enhances nutrient availability for your crop, critical during early growth stages. It also means weed flushes later in the season tend to be easier to manage in-crop.
In-Crop Herbicide Programs for Wheat and Pulses
When it’s time for in-crop spraying, choose herbicides for wheat that offer different active ingredients and modes of action from those used earlier in the season. In a Nufarm cereal program, that could mean:
- Oxbow® (Group 4, 6) or Enforcer® (Group 4, 6) herbicides for broadleaf control
- Epic® or Signal® (both Group 1) herbicides for grassy weed control
If you’ve used glyphosate (Group 9), Fierce EZ (Group 14, 15), and BlackHawk EVO (Group 4, 14) earlier, then adding Oxbow and Epic/Signal gives you six different modes of action over the season and eight unique actives—a solid strategy for managing resistance.
For pulse crops, Nufarm’s season-long program might include glyphosate, Fierce EZ, GoldWing (Group 4, 14), and Ransack® (Group 2, 6). This offers multiple modes of action for broadleaf and grass weeds, ensuring robust protection across weed species, making it a strong foundation when selecting herbicides for peas.
Scout and Adjust: A Long-Term Mindset
Regardless of the crop—cereals, pulses, or canola—scouting before and after herbicide application is essential. Watch for weed escapes, identify potential resistance issues, and adjust your plan accordingly.
Work with your agronomist or Nufarm representative to design a long-term herbicide rotation plan. Your strategy should:
- Use multiple, effective modes of action at all times
- Rotate herbicide groups from season to season
- Incorporate soil-active and pre-seed burndown applications
Weeds thrive on predictability. Mix up your approach to disrupt their lifecycle. Changing your application timing or introducing a product you haven’t used before can tip the balance in your favour.
Take Action Today
Herbicide resistance isn’t going away—but we can slow it down. Whether you’re choosing herbicides for wheat, herbicides for peas, or managing multiple crops across your rotation, taking a strategic, proactive approach will help protect your yields and your herbicide options.
