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Fighting the toughest weeds in Western Canada
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Fighting the toughest weeds in Western Canada

Mar 01, 2019

With the increased opportunity of corn and soybeans in Western Canada, farmers will have the opportunity to increase the diversity in their rotation. Increased crop diversity in combination with sound agronomic practices such as rotating herbicides, tank mixing and periodic tillage, are key to having a strong integrated weed management plan.

Another important component of a strong plan is understanding the challenges presented by the spectrum of weeds in the field. To help you with that we’ve compiled a list of some of the most persistent weeds you’ll face on your farm this spring.




Foxtail Barley

Description: A shallow-rooted, annual, grassy weed that produces seeds which can remain viable in soil for approximately three years. Germination usually takes place late May or early June and can continue until September.


Possible Impact: Yields can be reduced up to 25% from weed populations of 400 to 500 plants per square metre. Losses could be even greater during hotter summers.

Control Tips

  • Scout fields frequently for this weed as it grows fast in the heat
  • At approximately 34,000 seeds per plant, it’s a heavy seed producer; however, it’s a poor competitor. Healthy crop stand establishment will help your crop outcompete this weed.


Wild Oats

Description: A competitive, annual, grassy weed with a fibrous and extensive root system which grows best in cool weather and moist soil. Wild oat mostly germinates and emerges in early to mid-spring. Although most seeds germinate within two years, they can remain dormant in soil for up to eight years.

Wild Oats

Possible Impact: Approximately 10 wild oat plants per square metre can reduce wheat, barley and canola yields by 10% and flax up to 20%.

Control Tips

  • Summer fallow increases the number of seeds that break dormancy, and weeds will emerge after each tillage operation. Fall tillage also helps reduce wild oat populations.
  • When scouting, check low spots in fields for wild oats, as well as keeping an eye out for herbicide-resistant patches.
  • There are populations of wild oats resistant to Group 1, 2 and 8 herbicide products in Western Canada. To combat that, use a diversity of methods, and where possible, consider including a residual herbicide product to add an additional mode of action.


Wild buckwheat

Description: A vine-like, annual, broadleaf weed, which reproduces by seed.

Wild Buckwheat

Possible Impact: Although this weed can cause yield reduction, the larger issue is its climbing nature, which causes crops to lodge and makes swathing and combining difficult.

Control Tips

  • When scouting, check moist, low-lying areas.
  • A pre-seed burndown is recommended with no-till systems.
  • Scout fields early because wild buckwheat is most sensitive to herbicides during the initial growth stages.
  • Roundup WeatherMAX® herbicide provides excellent control of Group 2 resistant wild buckwheat. Include an effective tank-mix partner with your glyphosate application to reduce selection pressure and help prevent the development of glyphosate-resistant weeds.



Description: A competitive annual or winter annual weed, which prefers damp, moist soil. Cleavers reproduce by seed and germinate mid-spring. The seed is dormant in dry soil and can remain viable up to three years. The size and shape of cleaver seed make it difficult to separate from canola and can drastically lower seed quality.


Possible Impact: In heavily infested fields, it can cause significant yield loss. For example, 100 plants per square metre can result in yield reductions up to 20% in canola.

Control Tips

  • Apply an effective herbicide tank mix at the one- to two-whorl stage. Past that point, cleavers will not be controlled consistently.
  • Seed early or delay seeding until weeds emerge in cleaver-infested fields.
  • Use herbicides and tillage after weed germination in the fall to control winter annual cleavers.
  • Include cereals and annual and perennial forages in your rotation to reduce weed populations.
  • In fields heavily infested with cleavers, consider growing a canola system that provides in-crop control of populations.


Canada thistle

Description: a perennial, broadleaf weed that spreads rapidly, is a strong competitor and its green matter slows harvesting. It reproduces by seed and from horizontal root stalks. Shoots from the horizontal roots appear on the soil surface around mid-April and continue to emerge throughout the summer. Seed germinates from late May through to the fall and can be dormant for up to 20 years.

Canada Thistle

Possible Impact: Responsible for more crop loss than any other broadleaf weed in Western Canada

Control Tips

  • Requires a multi-year combination of chemical and cultural control practices. Root starvation is important to weed control. In addition, prevention of plant establishment and spread is essential.
  • Use effective crop rotations with strong competitors to thistle.
  • Top growth can be suppressed in a number of crops by herbicides; however, roots and shoots can grow into new plants.
  • The best time to control Canada thistle with a glyphosate application is in the fall when the plant starts sending nutrient reserves down to its root system.

More help is here

The introduction of TruFlex™ canola with Roundup Ready® Technology, with its increased  flexibility when compared to Roundup Ready® canola to use targeted rates and timings, will also assist Western Canadian farmers in their battle against challenging weeds.

With the TruFlex™ canola system, you can control a broader spectrum of weeds than was possible with Roundup Ready® canola – further enhancing your operation’s weed management plan.


To learn more about canola’s next generation, visit





“Green Foxtail (Foxtail Barley).” Manitoba Agriculture, Food and Rural Development. Government of Manitoba, n.d. Web. 4 Apr. 2016.

“Wild Oats.” Manitoba Agriculture, Food and Rural Development. Government of Manitoba n.d. Web. 4 Apr. 2016.

“Cleavers.” Manitoba Agriculture, Food and Rural Development. Government of Manitoba, n.d. Web. 4 Apr. 2016.

Beckie, Hugh J. “State of weed resistance in Western Canada and future outlook.” Sask Wheat Development Commission. 2016. Online. Accessed Jan. 26, 2017.