When it comes to the High Plains and Intermountain West collectively, there's likely no grass species more synonymous with the word "invasive" than cheatgrass. It's been said that cheatgrass infests more than 100 million acres in the High Plains and Intermountain West. And once it matures and dries out in the summer, it's like gasoline for wildfires.
Native to parts of Europe, Africa and Asia, the annual grass typically matures about early June, and once it does, it becomes much less palatable, and cattle tend to avoid it. It matures and dries out much earlier than perennial grasses, making it great fuel for wildfires.
Cheatgrass is spread throughout most of the U.S., although it's most prominent in the Great Plains and Great Basin, where it has spread in part because of overgrazing more desirable perennial grasses, giving it an opportunity to take over native ranges. And if untreated after a wildfire, it doesn't take long for cheatgrass to create a monoculture.
According to the Sage Grouse Initiative's website, cheatgrass has a shallow root system, with most of its roots in the top 12 inches of soil, allowing it to absorb much of the water and nutrients early in the growing season and outcompete native plants for those limited resources.
The question is, with such pervasive expansion of cheatgrass, what strategies can be used to control or even reduce its spread?
When it comes to grazing, the best strategy to control cheatgrass is to limit the number of seeds produced each year by grazing it earlier. As an invasive annual grass, it's actually palatable early in the growing season.
Research conducted by Mitch Stephenson, Nebraska Extension range and forage management specialist, at the University of Nebraska's Panhandle Research and Extension Center and USDA's Agricultural Research Service High Plains Grassland research station near Cheyenne, Wyo., found that cattle tended to select cheatgrass heavily in April and May, but stopped in early June.
However, about the same time cheatgrass is most palatable, more desirable native cool-season grasses such as needle-and-thread grass and western wheatgrass are coming out of dormancy. The challenge is avoiding overgrazing the perennials when they're vulnerable, while also knocking cheatgrass back at the right time.
In 2016 and 2017, Nebraska Extension educators and specialists competed with University of Wyoming Extension, the Wyoming Reclamation and Restoration Center, Wyoming Weed and Pest Control, and Wyoming Society for Range Management as part of the University of Wyoming Cheatgrass Challenge.
The competition involved managing a quarter-acre of land near Lingle, Wyo., that, after years of continuous set-stocked grazing, became dominated by cheatgrass and other weeds. Over those two years, teams were allowed to use any legal means necessary to control cheatgrass and kochia before the contest ended in the summer of 2017.
The practices used included attempting to smoke everything with glyphosate, using tillage to control weeds and replant native perennials in their place, and seeding cover crops and grazing to put additional pressure on weeds.
The Nebraska team mowed its plot several times to give native perennials and other desirable species a better chance to thrive and put continued pressure on weeds, and sprayed dicamba and 2,4-D to get a handle on broadleaves and kochia.
They also seeded native grasses to crowd out the weed population and experimented with a biological soil amendment product developed by USDA's Agricultural Research Service that uses naturally occurring bacteria that colonizes on roots of certain grass species, such as goatgrass, cheatgrass and medusa head, and suppresses root growth.
The winner of the challenge, a team made up of Wyoming ranchers and the USDA Natural Resources Conservation Service, focused on using intensive grazing practices to control cheatgrass.
However, Gary Stone, Nebraska Extension educator and member of the Nebraska Panhandle team, pointed out that mowing offered an alternative to grazing, which may be more efficient and timelier for those without adequate time, commitment or livestock to graze intensively.
Of course, for crop producers dealing with cheatgrass, there are a different set of challenges. For winter wheat growers in western Nebraska, one possibility is breaking up the fallow rotation and planting a crop such as yellow field peas.
A 2016 Nebraska Farmer article featuring Panhandle grower Mark Watson illustrates the benefits of introducing another crop to the rotation — in this case, using a three-year crop rotation with a pulse crop: field pea-corn-winter wheat.
Field peas are planted and harvested earlier, suppressing growth of plants such as cheatgrass, and breaking up weed and disease problems associated with summer fallow. That can be especially beneficial in years when rains prevent timely herbicide applications.
Herbicides also are effective, but are most effective when applied in late September through December. Although they can be applied in spring, efficacy dramatically decreases .
Other steps noted by Nebraska Extension include identifying how cheatgrass seed may be entering the land. Rangeland often is infested through contaminated hay, especially hay from early cuttings. And, after a year like 2019, with extreme weather and loads of donated hay rolling into the state, there's plenty of potential for cheatgrass seed to spread.
The bottom line is, there are several ways to control cheatgrass — including grazing, mowing, establishing competitive forages and herbicides — but they all depend on timing.