Weed control in wheat

By Greg LaBarge, Ohio State University Extension

Scouting wheat for potential weed issues is important to avoid yield loss or harvesting problems. When identifying a weed issue that requires a herbicide treatment, it is essential to apply herbicides at the correct stage of small grain growth to avoid crop injury. Making weed control decisions before or during Feekes 5.0 provides the greatest range of herbicide options. As wheat advances past jointing (Feekes 6.0) and approaches the boot stage, herbicide choices become limited. Most herbicides can be applied in UAN when the small grains are topdressed. However, applying herbicide in UAN can increase crop injury somewhat, and some labels recommend adjusting surfactant rates to minimize damage.

A few species to look for include.

• Wild garlic can contaminate harvested grain if the grain table picks up the aerial bulblets. Several herbicides are effective if applied in the spring after the garlic has several inches of new growth.
• Canada thistle seems to be making a comeback and can greatly suppress small grains growth due to its tendency to occur in dense patches. Many small grains herbicides have some activity on thistle and can suppress it adequately through harvest if not applied too early in spring.
• A healthy small grains crop can adequately suppress summer annual broadleaf weeds, such as common and giant ragweed, which can begin to emerge in late March. But a herbicide application is occasionally warranted.

The 2023 Weed Control Guide for Ohio, Indiana, Illinois, and Missouri is available for purchase here: https://extensionpubs.osu.edu/search.php?search_query=789&section=product in print or PDF.