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Sunday, March 31, 2019

The True Cost of Herbicide-Resistant Weeds

The True Cost of Herbicide-Resistant Weeds

In Australia, herbicide-resistant weed populations are increasing costs by about 27 percent per acre1 because of increased herbicide resistance management costs and yield loss. In the US, growers are paying up to $150/acre for hand weeding where no control options exist. Canada may not be trapped in those types of management nightmares yet, however, we are number three on the list of countries with the most herbicide-resistant biotypes.

The True Cost of Herbicide-Resistant Weeds

While many farmers are now taking measures to help control the spread of herbicide resistance, many others are waiting for the problem to have a direct impact on their farm. But the costs of waiting it out are too high. Once a weed species becomes resistant, it is here to stay and there are currently very limited options to reverse the situation. It then becomes a matter of what you can grow rather than what you want to grow. In a country with limited crop options, this could be a big problem.

Herbicide-resistant weeds result from repeatedly overusing a single mode of action. According to, there are currently 380 herbicide-resistant biotypes around the world. In Canada 58 are present – with 20 in Alberta, 20 in Manitoba and 17 in Saskatchewan. We have resistant weeds in cereals, corn, soybeans and pulses.

At this point resistant plants are here to stay, but their progress can be slowed. Best management practices include:

  • Tank mix herbicide Groups: to do this you need to read the labels and know your Groups. Some products have different names, but can have the same chemical makeup.
  • Prepare careful management records to ensure you rotate your crops. This not only changes weed profiles, but allows for the use of herbicides from different Groups.
  • Start out the season with clean fields so that crops can compete against early season weeds. Selective tillage can be used, or a burndown to eliminate weeds already in the field.
  • Correct herbicide application is important – always following label rates and recommendations.
  • If necessary, get into the field and control weed escapes manually. The goal is to prevent those weeds from setting seeds in subsequent seasons.
  • Always carefully clean your equipment to avoid field-to-field contamination.
  • Seed at competitive rates. Vary seeding dates and decrease row spacing – all to create more crop competition against weeds.
  • Ensure you time your fertility to feed the crops – not the weeds.

Herbicide-resistant weeds rob your crops of their yield potential, provide a host for disease and make harvest more difficult. Ensure you protect your farm with diverse systems, tools, products and skillsets. You can play a big part in keeping herbicide resistance in Canada under control.

For more information on implementing an effective Resistance Management Program on your farm, visit


  1. Grains Development Research Corporation (2014 ‒ 2015).