Recent rains have brought much needed moisture to the Kansas wheat crop. However, the moisture can also bring on winter annual weeds, especially in fields where poor wheat stands exist, or where continuous wheat or wheat-fallow rotations are used. This article will focus on the grass weeds common in wheat.
Like wheat, winter annual grasses typically emerge in the fall (although early spring emergence is possible), go dormant during the coldest months, and resume growth and produce seeds in the spring. The most common winter annual grasses infesting Kansas wheat are weedy bromes (downy brome, Japanese brome and cheat), jointed goatgrass, and feral rye. Generally, cheat and feral rye are typically found in the eastern parts of the state, whereas downy brome and jointed goatgrass are more often found in the west. Table 1 provides a list of postemergence herbicides labelled for these species and their efficacy on each species.
Table 1. Postemergence herbicides for winter annual grass control in Kansas1.
|
Herbicide |
Cheat |
Downy brome |
Japanese brome |
Jointed goatgrass |
|
|
Aggressor (CoAXium wheat only)2 |
G-E |
G-E |
G-E |
G-E |
G-E |
|
Batalium Amped |
F-G |
F-G |
F-G |
P-F |
- |
|
Beyond Xtra (Clearfield wheat only)2 |
E |
G-E |
E |
E |
G |
|
Everest 3.0 |
G-E |
P-F |
G-E |
- |
- |
|
Metribuzin |
F-G |
F |
G |
- |
- |
|
Olympus |
E |
F-G |
E |
P |
- |
|
Osprey |
F |
F |
F |
- |
- |
|
Outrider |
G-E |
F-G |
G-E |
- |
- |
|
Powerflex HL, GR1 |
E |
F-G |
E |
- |
- |
|
1 Ratings: E = excellent, G = Good, F = fair, P = poor, - = weed not listed on herbicide label. Products with residual activity are in bold. 2 Application of Aggressor to non-CoAXium wheat or Beyond Xtra to non-Clearfield wheat will result in severe crop injury. |
|||||
As a general rule, fall applications will provide better control of these weeds than spring applications. But, it is important to remember that weeds must be actively growing for herbicides to be effective. Be aware of temperatures in your area to make sure weeds are not dormant. Delaying applications until spring when the herbicide can be mixed with top-dress 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.
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 and allows for 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 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 (downy brome, feral rye, and jointed goatgrass) at wheat harvest can be a viable option for reducing the number of weed seeds that return to the soil seedbank, therefore reducing the pressure of winter annual grasses in the following seasons. More information on seed harvest 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 the weedy bromes. Jointed goatgrass and feral rye options are more limited, and will likely require that either a Clearfield or CoAXium wheat variety was seeded. In fields where winter annual grasses are known to be a problem, cultural practices can be implemented to reduce their impact, such as considering using a preemergence herbicide prior to wheat emergence or planning to use an herbicide-resistant wheat variety.
For additional information about these herbicides, see 2024 Chemical Weed Control for Field Crops, Pastures, Rangeland, and Noncropland, K-State publication SRP-1183.
The use of trade names is for clarity to readers and does not imply endorsement of a particular product, nor does exclusion imply non-approval. Always consult the herbicide label for the most current use requirements.
Patrick Geier, Weed Scientist, Garden City
pgeier@ksu.edu
Logan Simon, Southwest Area Agronomist, Garden City
lsimon@ksu.edu
Sarah Lancaster, Extension Weed Management Specialist
slancaster@ksu.edu
Jeremie Kouame, Weed Scientist, Agricultural Research Center – Hays
jkouame@ksu.edu
Tags: wheat weed control