Manage weed resistance in Western Canada through good herbicide choices

Category: Grow Grain

Variety may be the spice of life, but it’s the enemy of weeds. Here’s how to prevent resistance, slow its spread and spot it in the field.

Wild oats growing in a field

Patches are weed’s biggest tell – they’re the first sign that resistance is developing in your field and can be spotted during a herbicide efficacy walk. If you see weed patches that survived your in-crop application, you may have resistance. But with careful management, you can stop it from spreading in the field. 

Rotating your herbicide groups is the most effective way to prevent herbicide resistance or slow it down. It’s important to note that weeds develop resistance to a herbicide group, and simply changing brands doesn’t always mean changing modes of action. Switching from Simplicity™ to Varro™ may sound like you’re rotating herbicides, but both of these products are group 2 herbicides. Changing groups as you rotate crops and try to stay one step ahead of the weather can be very challenging. I encourage you to take a long-term view of weed management and think of it as a strategy for your farm.

Here’s an example: Let’s say you have group 1 wild oat resistance. You could switch from group 1 to group 2, but if you only spray group 2 year after year, you’ll likely develop group 2 wild oat resistance. You need a strategy that includes other modes of action (MOA), such as pre-plant incorporated herbicide or a product like Liberty® in the years you aren’t growing cereals. Both of these MOA will keep wild oats off balance, prevent resistance from developing and increase the length of time your Group 2 herbicide remains effective against them. 

For people who enjoy puzzles and have a lot of knowledge of herbicides, developing your weed management strategy can be a lot of fun. For everyone else, your agronomist can walk you through the process. They’ll take an overview of your whole farm as you answer the following questions:

  1. What weed resistance am I currently facing on each field?
  2. What is my next-choice product for controlling those weeds?
  3. What’s my backup plan if the weather doesn’t cooperate?

  4. What does my crop rotation look like?
  5. What does my herbicide rotation look like?
  6. What cultural options do I have?

I encourage you to talk to an agronomist about your weed management strategy. Yes, it can take a lot of work to plot all the variables. But like any good strategy, it will put you in the best position for long-term success. Contact your local Cargill retail location or call 1-888-855-8558 to connect with an agronomist in your region.


Always read and follow herbicide label directions.  Simplicity™ is a registered trademark of The Dow Chemical Company. Varro™ and Liberty® are registered trademarks of Bayer CropScience LP.

Tags: Crop Inputs, Herbicide, Weed Management

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