Beneficial rains have brought much-needed moisture to the Kansas wheat crop. However, the moisture can also trigger winter annual weeds, especially in fields with poor wheat stands or where continuous wheat or wheat-fallow rotations are used.
Like wheat, winter annual grasses typically emerge in the fall (although early spring emergence is possible). They go dormant during the coldest months, then resume growth and produce seeds in the spring. The weedy brome species cheatgrass (also known as downy brome), Japanese brome, and cheat are among the grass weeds most commonly found in Kansas wheat. Jointed goatgrass and feral rye are also prevalent and are especially challenging to control. Cheat and feral rye are typically found in the eastern parts of the state, whereas cheatgrass and jointed goatgrass are more often found in the west. For specific information about postemergence herbicides for controlling winter annual grasses, refer to the K-State Agronomy eUpdate electronic newsletter by typing that into your internet browser.
Considerations for Herbicide Applications - as a general rule, fall applications will provide better control of these weeds than spring applications. However, it is important to remember that weeds must be actively growing for herbicides to be effective. Be aware of the temperatures in your area to ensure weeds are not dormant. One temperature guideline to consider using is low temperatures above freezing and high temperatures above 50°F for three to five days before and after the application. Delaying applications until spring, when herbicide can be mixed with topdress fertilizer, is an option, although this can lead to greater yield loss due to competition and reduced herbicide efficacy. Furthermore, spring applications may not meet crop rotation intervals. Always read the herbicide label to determine recropping intervals and adjuvant requirements. The growth stage is also important when applying several of these herbicides.
Other Options: Crop Rotation and Seed Destruction - crop rotation is an effective method of preventing winter annual weeds in wheat. One or more summer annual crops between wheat crops disrupts the life cycle of winter annual weeds, allowing for the use of other cultural and chemical methods for their control. Narrower row spacings or increased wheat seeding rates can make wheat more competitive with weeds. In dry environments, seeding wheat deeper into moist soil may allow wheat to emerge before weedy brome seeds that must germinate from dry soil nearer the soil surface. Alternatively, delaying planting until after the first flush of weedy grasses has emerged may also be an effective cultural management practice when moisture is abundant.
Seed destruction of some winter annual grasses (cheatgrass, feral rye, and jointed goatgrass) at wheat harvest may be a viable option to reduce the amount of weed seed that returns to the soil seedbank, which may reduce the density of winter annual grasses in the following seasons. More information on harvest weed seed destruction can be found at: https://eupdate.agronomy.ksu.edu/article/harvest-weed-seed-destruction-a-tool-for-managing-herbicide-resistant-weeds-601-1
Summary: Several effective options exist to control weedy brome species. Jointed goatgrass and feral rye control options are more limited and will likely require planting either a Clearfield or CoAXium wheat variety. In fields where winter annual grasses are known to be a problem, cultural practices can be implemented to reduce their impact, such as using an herbicide-resistant wheat variety or rotating to a summer crop.
For additional information about these herbicides, see 2025 Chemical Weed Control for Field Crops, Pastures, Rangeland, and Noncropland, K-State publication SRP-1190.
Stacy Campbell is an Agriculture and Natural Resources agent for Cottonwood Extension District. Email him at scampbel@ksu.edu or call the Hays office, 785-628-9430.
