Wheat competes well with weeds especially when good production techniques result in an initial uniform stand establishment and when loss of stand due to winter injury is minimal. Effective weed control and prevention of weed seed production in prior crops will reduce the risk of weed problems in wheat. Some wheat fields can benefit greatly from herbicide application, and failure to scout fields and take the appropriate measures can result in yield loss and harvesting problems in these fields. The weeds that appear above the wheat canopy late in the season, such as ragweed and Canada thistle, can often be easily controlled with a spring herbicide treatment.
The most common weed problems in wheat include:
- Winter annual weeds, such as common chickweed, purple deadnettle, shepherd’s purse, and field pennycress. These weeds become established in the fall along with the wheat and can interfere with early development of wheat in the spring. Dense populations of winter annual weeds should be controlled in late fall or early spring to minimize interference with wheat growth.
- Wild garlic, which contaminates harvested grain with its bulblets. Several herbicides are effective if applied in the spring after garlic has several inches of new growth.
- Canada thistle, which can greatly suppress wheat growth due to its tendency to occur in dense patches. Most wheat herbicides have some activity on thistle and can suppress it adequately, if not applied too early in spring.
- Summer annual broadleaf weeds, such as common and giant ragweed, which can begin to emerge in late March. A healthy wheat crop can adequately suppress these weeds, but herbicide application is occasionally warranted.
Specific chemical weed control recommendations can be found in the Weed Control Guide, Extension Bulletin 789, available at all County Extension offices and online at CFAES publications at: estore.osu-extension.org/.