With current commodity prices, there is much more interest in growing wheat for grain. This means that the cool-season annual grasses that were used as forage when fields were grazed and/or hayed are now weeds that need to be controlled. This article is meant to offer herbicide suggestions and is not meant to provide specific recommendations for all producers and all fields.
There are several problem grasses that we commonly see in southern Oklahoma wheat grain production. They are rye (Secale cereale), ryegrass (Lolium multiflorum), cheat, downy brome, Japanese brome, rescuegrass (Bromus sp.) and wild oat (Avena fatua). Unfortunately, there is no single herbicide that does a good job on all of these. In fact, no single herbicide is equally effective on all of the brome species. However, the included tables display the different grasses and the herbicides labeled to control them and the different herbicides and the grasses they are good at controlling.
There are some specific notes I would like to share about some of these grasses. As already mentioned, not all bromes are equally controlled by the same herbicides. Olympus® 70% may be a good choice for bromes when applied as a fall postemerge herbicide. Another good option may be planting a "Clearfield®" wheat variety and using Beyond® herbicide. Beyond® herbicide will control a broad spectrum of grasses, but can only be used on wheat with tolerance to this herbicide. Beyond® herbicide with a "Clearfield®" wheat variety is also the only practical option for control of volunteer cereal rye. Glean® can provide significant suppression and/or control of ryegrass and many other weeds when applied as a pre-emergent herbicide. Ryegrass can be controlled postemergent with Axial® or Osprey®. Osprey® also works well on wild oat.
With these and all herbicides, there are some important things to remember.
- Weed size - Treat the target weeds when they are within the size range listed on the label.
- Weather - Be careful of high temperatures, freezing temperatures, rainfall or lack of rainfall, and other stresses on the weeds and the crop.
- Grazing restrictions - Some herbicides do not allow grazing of the forage for a period of time after application.
- Carryover - This is a big one. Some herbicides restrict planting of various crops for up to 18 months after application. If you have any intentions of rotation or double-cropping, be sure to check the herbicide label for safe plant-back dates.
- Herbicide resistance by weeds - As always, don't rely on herbicides with the same mode of action year after year.
- Finally and most importantly, always read and follow label directions.