Control of perennial and winter annual weeds
Perennial weeds are best controlled in early fall when they are still actively growing. They can be controlled with either a Pre-harvest or post-harvest herbicide application. Pre-harvest herbicide is an effective tool if the residue and the pre-harvest interval requirements are met. Post-harvest herbicide requires enough regrowth after harvest for the application to be effective.
Learn more at:
Winter annual and perennial weed control – Alberta Agriculture and Irrigation