From labels and weed guides
Best herbicides for canada thistle in flax
For canada thistle in flax, the weed guides list 2 active-ingredient groups rated good or excellent, after checking that the products are labeled for flax.
Canada Thistle control in flax
Every listed product is labeled for flax. Ratings are shown when each weed guide that rates this weed stays at good or excellent for the active-ingredient group. If a guide gives a range, the weaker end of the range has to be good or excellent.
Based on 1 weed guide, 2 active-ingredient groups are rated good or excellent for canada thistle in flax.
| Example product | Active ingredients | MOA group | Ratings checked |
|---|---|---|---|
| Curtail M EPA 62719-86 | clopyralid and mcpa | 4 | ND Weed Guide 2026: G-E (PDF) |
| Stinger HL EPA 62719-747 | clopyralid | 4 | ND Weed Guide 2026: E (PDF) |
Rating legend: E=excellent, G=good, F=fair, P=poor, N=no control. A range such as G-E means the guide gives a range; 'a' after a rating (e.g., Ga) means the guide assumes its recommended additive.
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Sources
Data from current labels and weed guides. Last source update: 2026-07-14.