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Cheatgrass continues as discussion topic in Wyo

by Wyoming Livestock Roundup

Cody – Landowners from around the Cody area gathered on April 4 for a workshop by University of Wyoming Sheridan Research and Extension Center Director Brian Mealor on cheatgrass management, funding and local prevalence.

“For a long time, we thought there was an upper elevation limit, but within the last 10 years, we’ve seen upward expansions and movement into areas cheatgrass hadn’t previously occurred,” said Mealor.


Cheatgrass is primarily a winter annual plant, meaning that its top priority is seed production, said Mealor.

“It doesn’t invest a lot of resources into structure development, but it can get a lot of fibrous roots. It’s really good at taking up moisture from snowmelt,” he explained.

Mealor noted that moisture has a large impact on when cheatgrass will germinate.

“If we get fall moisture, most of the cheatgrass in this area will germinate in the fall,” said Mealor.

According to Mealor, if cheatgrass overwinters, or vernalizes as a seedling, the plant will produce more seeds than if it vernalizes as a seed.

The cold period is critical to cheatgrass reproduction, he commented, explaining, “If it doesn’t vernalize, it doesn’t go through to seed.”

Cheatgrass density also influences seed production of individual plants.

“When it’s really thick, each plant produces fewer seeds per plant, but if we thin it out, they produce more seed per plant, so we end up with pretty consistent seed production,” he continued.


While many landowners think that native perennial biomass declines because of an increase in cheatgrass, Mealor explained that the increase in cheatgrass can be because of increased bare ground, as well.

“It’s a chicken and egg thing. We do know that cheatgrass is highly competitive for moisture in the early spring, which is part of why it becomes such a problem,” he said.

Cheatgrass presence is also able to change landscapes, particularly when looking at the example of changing fire intervals.

“Fire doesn’t always equal cheatgrass, but a high amount of cheatgrass does increase the risk of a fire,” commented Mealor.

He continued, “If we look at traditional historical fire intervals, it is safe to assume we see fires every 40 to 50 years. There are places along the Snake River that burn every three to five years.”

The prolific seed production of cheatgrass is another factor that makes it highly competitive with native species, producing 400 pounds of seed per acre.

“It stays viable in the ground from five to seven years,” commented Mealor. “If we’ve only got 10 percent carry over, that’s still a lot of seed.”


While many treatments exist and the plant itself is not difficult to kill, Mealor stressed, “One treatment is not enough because of seed viability. Biology informs management. There is no silver bullet. It’s a long-term sort of commitment.”

Chemical control is one of the most common and effective methods for both short-term and long-term control.

The most common chemical used is Imazapic, also know as Plateau, which does not having any grazing limitations after application.

Imazapic may also be mixed with glyphosphate, but landowners should be aware that the chemicals will not be selective.

Other chemicals including Matrix, which is available as the off-brand. Laramie, Canter R+P, Landmark EP and Outrider are also available but have differing requirements than Plateau for application rate and grazing.

“It’s open to interpretation, but the way I read the Matrix label, there can be no grazing for one year after application,” he continued.

Mealor noted that a new herbicide called Esplinon that is currently in trials.

“It’s a root growth inhibitor. It doesn’t affect established grasses at all,” he said.

Grazing is another common method that landowners use when managing cheatgrass.

“In some cases it works, but ‘work’ is relative. The results are a little more subtle,” continued Mealor.

However, grazing can be particularly effective when used in combination with other control methods.

“When we don’t graze, we get a buildup of litter. Cheatgrass emergence and establishment is facilitated by a litter layer,” he said.

A large amount of research is currently being done on utilizing various bacterial and fungal strains as biological control methods, but many concerns about practicality must be addressed.

“At this point, I don’t think we have an adequate biological control method,” noted Mealor.


Several factors should be considered when deciding whether to treat a particular site.

“Timing is important. If the plants gets too big, our treatment is just not going to be effective in killing the cheatgrass,” said Mealor.

Landowners should also consider how much natural recovery potential there is at a site.

“Is there some natural recovery potential on the site? We can get the herbicide to do exactly what we want it to, but there’s just bare ground,” he commented. “Then we’re talking about a restoration project and not a weed control project.”

Mealor continued, “I firmly believe that the best long-term suppression comes from a healthy perennial plant community. If it comes to the point that we need to reseed, we’re not going to have long-term suppression.”

Mealor outlined three key considerations when making decisions at landscape level.

“One, leverage is important. Next, every tool has its limitations and finally, there are some unintended consequences of doing a good thing that we should be prepared for,” said Mealor.

Emilee Gibb is editor of Wyoming Livestock Roundup and can be reached at

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