Herbicide resistance plan of action

A plan of action

It’s an old adage but it still holds true: if you fail to plan, you plan to fail. Mixing It Up is no different. The good news is that everyday farming practices – like rotation, selection and seeding – are effective ways you can take action against resistance.

Here are ways you can incorporate diversity into your plan moving forward.

Herbicide management


Rotate herbicides and Groups

Managing herbicide resistance depends on rotating modes of action. Weeds that possess the inherent ability to survive an application of certain herbicides eventually multiply and spread, and can create potential problems down the road.
Herbicide selection for difficult weeds

Herbicide selection

  • Match the herbicide(s) to your most difficult weeds
  • Apply multiple herbicide Groups that are effective on target weeds
  • Rotate herbicide Groups

Maximizing herbicide performance

  • Use full-labeled rates
  • Include the best tank mixes & adjuvants
  • Use correct nozzle spacing, droplet size and water volumes
  • Avoid spraying at excessive speeds
  • Apply during the best weather conditions
  • Observe rain-fastness intervals
  • Optimize application by spraying between 8 a.m. and 9 p.m.
  • Make sure your equipment is
    properly calibrated

Field management


The importance of field records

If you don’t have a record of what’s been sprayed on which field over the past 5 years, it’s time to start one. If you only have product names in your records, they need to be translated into herbicide Groups. For example, if you find that you have been spraying Group 1 herbicides for 4 out of the past 5 years on the same field, it may explain why your weed control program is losing
its punch.

Crop rotation

Rotating crops annually adds diversity to the field cropping system, and diversity increases the sustainability of the system. It provides the platform for long-term weed management. A well-planned crop rotation can:
  • Reduce the impact of weeds, insects and diseases, leading to higher yields
  • Lower input costs in some rotational crops
  • Use more competitive crops to control weeds in some years
  • Help manage crop residue
  • Provide diversified marketing options
  • Give you the option to choose different herbicide Groups


Seed competitive varieties and increase seeding rates to enhance a crop's ability to compete more effectively with weeds. Varying seeding dates and decreasing row spacings are other options. Even herbicide-resistant weeds are still susceptible to crop competition for space, moisture, sunlight and nutrients.

A very effective way to prevent herbicide resistance is to seed your problem field last*. Delaying seeding allows the weeds to grow so you can eliminate them.

*Source: 5 year UK study supports this seeding later


If tillage is an option, for minimum till or no-till operations the consideration of selective tillage adds a tool to your toolbox. Focus on problematic weed patches.



Crops that get a head start on weeds through proper fertility are going to be more competitive. Plan a fertility program for the crop; feed the crop, not weeds.


Sample collection for HR testing

If, after going through these warning signs, you suspect that you have a resistant weed population, collect a sample of the plants and/or seeds for testing. See Resources for contact information for herbicide resistance testing sites.

Proper sample collection that includes multiple plants and/or adequate seed volume is critical for accurate testing. Testing labs will provide specific guidance for sample submissions.


The worst thing you can do is nothing

Taking action now, before resistance becomes a bigger issue in Canada, is the best way that all of us together can manage the problem.

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