The effectiveness depends on the size of the weeds at application. Products that can work very well on Canada thistle are Stinger, Curtail and Express. Any herbicide labeled for wheat can be safely applied before jointing. Don't stage wheat based on the plant height, Loux says. Top-dressing herbicides in a nitrogen fertilizer solution can be convenient, but also can increase injury, Loux says.
Some labels recommend adjusting surfactant rates to minimize injury.
Always follow product labels for application timing and other safety procedures, Loux says. A few can be applied as late as early boot, although injury risk increases after jointing. To minimize risk of injury after jointing, use water as the carrier and do not apply more than a half pint of ester or 1 pint of amine. 2-4,D will not control chickweed or henbit and can be weak on smartweed and deadnettle. It's not as effective as 2-4,D on mustard species but is more effective on smartweed and weak on chickweed, deadnettle, henbit and wild garlic.