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You Are Here Growers > Weeds > Canada Thistle

Canada Thistle (Cirsium arvense)

Canada thistle
This weed rated the worst weed in Manitoba and the second worst weed in North Dakota in 2008. Canada thistle is a perennial and can spread by seed or rhizome. The seed spreads easily and germinates quickly.

Control Strategies

Canada Thistle
1. Fall burn down is necessary prior to a hard frost, when regrowth is 8-12 inches tall and soil moisture is good. Glyphosate combined with other herbicides can provide good results

2. Express˛ is the only sunflower labeled herbicide that has good to excellent activity on Canada thistle

3. Between row cultivation or hooded sprayer herbicide application

4. Sunflower fields with Canada thistle should be burned down with Glyphosate when sunflower seeds are 35% moisture or below.

Additional Links

Colorado Weed Management Guide (link)

Glyphosate, Weeds, and Crops (link)

KSU Weed Publications (link)

NDSU Crop Production and Marketing (link)

SDSU Weed Control in Oilseed Crops (link)

Sunflower labeled Herbicides (link)

Contact the chemical companies to obtain a copy of the label.


Express herbicide is specific to ExpressSun® hybrids only. ExpressSun hybrids have been developed with a resistant gene to Express herbicide. Applying Express herbicide on non-ExpressSun hybrids will result in extensive damage.

Glyphosate and Aim are labeled for between row hooded sprayer applications.

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