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Smith: Cheatgrass armies can be defeated across Wyoming with management

by Wyoming Livestock Roundup

Worland – Cheatgrass is an ongoing invasive concern across Wyoming, and University of Wyoming Extension Northwest Area Rangeland Resources Educator Mae Smith noted that great work is going on around the state, but rangeland managers must be proactive in winning the war against cheatgrass. 

“Individually, cheatgrass is kind of weak, but in millions, it is able to gain on natives,” Smith said at WESTI Ag Days on Feb. 3. “They overwhelm the native population.”

Using the analogy of an army of cheatgrass attacking our native grass, Smith described the challenges of dealing with cheatgrass and looked at the tactics we can use to win the war against the invasive plant.

Preventing invasion

Despite the number of factors acting against native rangelands, Smith said, “If we don’t pick a fight with cheatgrass, we won’t have to win the war.”

She clarified her point, noting that anything that can be done to prevent cheatgrass from entering and invading rangeland systems is important. 

“I’ve heard it said many times before that we should manage for what we want, not what we don’t want,” Smith said. “Proper grazing management, rotational grazing and reduction of disturbance can prevent cheatgrass infiltration.”

Maintaining strong, healthy rangelands is the most important factor in resisting cheatgrass invasions. 

Environmental factors

However, if cheatgrass does enter an area, there are some actions that can be taken. 

Particularly when reclaiming lands, Smith said that decreasing the available nitrogen in the soil can reduce invasions. 

“Cheatgrass really likes nitrogen,” she explained. “It will come into places with high nitrogen, such as areas that have just experienced fire or reclaimed areas that have been fertilized. By adding carbon to the system, soil microbes convert and use the nitrogen so it isn’t available for cheatgrass.”

One potential strategy is to spread sugar in small areas where cheatgrass is invading. While it isn’t cost effective to spread sugar across large areas, by spreading it across small areas, cheatgrass invasion can be minimized. 

“We should make the environment as inhospitable as we can,” Smith said. 

Targeted response

Targeting the areas where cheatgrass is most likely to occur and invade can also be beneficial. Cara Noseworthy, a University of Wyoming master’s degree student, has developed a map to represent the probability of cheatgrass becoming established and the relative abundance the plant would have in Wyoming. 

“There are a couple of areas across the state where there is a higher probability of cheatgrass dominance,” Smith mentioned. “Hopefully that will be useful in driving some management objectives that we have.”

The model will serve to determine where intensive management and control efforts will be most effective.


Chemical warfare, or use of herbicides, Smith said, is widely used in addressing cheatgrass.

“There are several herbicides that are labeled for cheatgrass management,” Smith said. “Many of these herbicides are sprayed pre-emergent – or before the cheatgrass even comes up.”

Because of the rapid life cycle of cheatgrass, she mentioned that it is often more effective to apply herbicide before the plant emerges.

Biological control

Several biological control methods are also available for cheatgrass, Smith mentioned. 

“The first is a rhizobacteria called Pseudomonas fluorescens,” she said. “The bacterium produces a toxin that attacks the roots of cheatgrass and reduces the ability of the plant to grow.”

Secondly, a fungus called Black Fingers of Death can be utilized to control cheatgrass. The fungus attacks seeds and reduces their viability. 

“Black Fingers of Death reduces the viability of seeds. It does not eliminate all of the seeds,” Smith clarified. “Therefore, we aren’t eliminating the problem.”

Utilizing livestock

Finally, grazing can be used as an effective control method for cheatgrass. 

“Another study by Cara Noseworthy is hot off the press and looks at sheep and cattle grazing trials for cheatgrass,” Smith said. “Cara still has another season to analyze, but she is hoping to determine the effectiveness of targeted grazing as a method of controlling cheatgrass.”

The study compared spring grazing, fall grazing and both spring and fall grazing of both cattle and sheep to herbicide application. It employed a high utilization rate to most effectively combat the cheatgrass. 

“They did find that livestock grazing was effective at decreasing the biomass, seed production and cover of cheatgrass,” Smith noted.

However, as cheatgrass is removed, it is necessary to have a strong native population to avoid invasion of other weeds. In the study, kochia returned where cheatgrass was removed. 

“Targeted grazing is effective on cheatgrass,” she said.

“We have quite a few tactics to address cheatgrass,” Smith commented, “but cheatgrass has quite a few invasion tactics. Hopefully we can bolster our offense and use all of the tools in our toolbox to overcome the invader.”

Cheatgrass biology

“Cheatgrass germinates in the fall,” Mae Smith, University of Wyoming Extension Northwest Area rangeland resources educator, said. “He is recruited into the cheatgrass army in the fall and trains all winter long. In the spring, he is ready to attack.”

Smith continued that cheatgrass dies early in the summer, spreading its seeds to prepare for the next year. 

At the same time, dead cheatgrass provides cover for the new seeds, as well as fuel for fire. 

“Cheatgrass has some innovative tactics for surviving,” Smith said. 

“First, cheatgrass is an early riser,” she explained. “In the spring, cheatgrass emerges before our native plants. It has the jump on us and steal all of the resources of our natives. That is tough to overcome.”

In addition to its ability to out-compete native grasses, cheatgrass thrives in fire aftermath and also stimulates fire occurrence by providing abundant fuel. 

“As cheatgrass dies, the litter that builds up burns easily,” Smith said. “Any lightning strike can burn a whole area up.”

“As a strong sagebrush community, most of our rangeland only burns every 30 to 200 years,” she continued, “but cheatgrass likes to burn. It is a really good tactic to keep natives from thriving.”

Finally, cheatgrass has phenotypic plasticity, meaning that it is very adaptable. 

“If cheatgrass is in a mountain environment, it may be smaller,” she explained. “In a newly burned environment, it produces big, strong plants because it really likes the nitrogen from freshly-burned areas.”

“Cheatgrass is able to adapt and change according to what the environment looks like,” Smith said. 

On the other side, native species tend to be less capable of adapting to rapid changes in the environment. 

“Native grasses are pretty set in their ways and like to have the same environment consistently,” she says. “Cheatgrass can change very quickly. Cheatgrass can infiltrate and destroy our native rangelands.”

Saige Albert is managing editor of the Wyoming Livestock Roundup and can be reached at

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