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Ventenata, medusahead headlight invasive weed tour

by Wyoming Livestock Roundup

Sheridan – For the first time, ventenata grass and medusahead were discovered outside the Great Basin last year in Sheridan County. Both grasses are invasive and present problems that outweigh the impacts seen from cheatgrass in the state.

“When I speak to weed scientists in Idaho, Oregon and part of California, they say they would trade every acre of ventenata and medusahead to get cheatgrass back,” said Brian Mealor, director of University of Wyoming’s (UW) Sheridan Research and Extension Center.

On June 14, the Northeast Wyoming Invasive Grass Working Group hosted a tour where over 80 weed specialists, landowners and others from five states gathered to learn more about the two unique and concerning invasive species.

“There is a lot of interest in these species, particularly since this is the first occurrence of both of these species outside the Great Basin,” Mealor said. “This was really a good opportunity for people to know what to look for and learn more about these species.”


Both ventenata grass and medusahead dramatically reduce forage quality of rangelands.

“In heavily infested areas, ventenata and medusahead can reduce forage quality by 70 percent,” Mealor said. “If we get livestock on it early enough – when there isn’t much else to choose from – they’ll use it. But, these grasses sequester silica out of the soil, which is basically sand. It’s no wonder why cows don’t want to eat it.”

“The forage value of medusahead is really limited, too. It has a stem and pointed seed head. There are almost no leaves on it at all,” Mealor said.


When looking at ventenata grass, Mealor explained that it is dispersed across 750,000 acres in northeast Wyoming.

“Last May, we didn’t think ventenata existed in Wyoming,” he said. “By the end of October, when we connected the dots, we have about a 750,000-acre distribution of it.”

The quick recognition of the species was due to the vigilance of landowners, who were willing to look for the plant and contact weed specialists when they found it.

“Ventenata is much more widespread than we originally thought,” Mealor added.


While ventenata grass is concerning, Mealor noted that medusahead causes him considerably more concern.

“Medusahead is, by all accounts, more difficult to control than the other grasses,” he said. “This has been on our radar over the last 10 to 12 years.”

Over the last decade, Mealor said he has deployed survey crews, primarily in Uinta and Lincoln counties, to see if medusahead breached Wyoming’s borders.

“The nearest documented location of medusahead to Wyoming was on Utah State University’s Hardware Ranch, 28 linear miles from the Lincoln County line,” Mealor explained. “When it cropped up in Sheridan County last year, we were all scratching our heads on how it got there.”


Medusahead has long awns that get longer as the plant starts to mature.

“As the inflorescence starts to mature, the awns on the bottom portion get noticeably shorter than the ones on the top,” Mealor explained. “It looks like it had a haircut.”

At the same time, the awns are long, barbed and rough. They are also sharp and twisted, making it even less palatable for livestock.

“Medusahead is bright green in color, and it’s just now starting to turn neon green,” he said. “We’re trying to capitalize on that to get out and identify where it’s at.”

Addressing the species

“We were hoping to never deal with ventenata or medusahead. Now, we have to decide what our strategy and course of action should be,” Mealor said.

As of June 7, three locations northwest of Sheridan and near the Montana border have documented medusahead populations.

“At this point, the three known populations are relatively small, but we don’t know if they reflect the full species distribution,” he continued. “If they do reflect full distribution, we hope to do aggressive treatments to eradicate the species.”

To aggressively target both medusahead and ventenata, the Northeast Wyoming Invasive Grass Working Group has banded together, bringing together a number of land management agencies, local governments, landowners, university researchers and Extension professionals.

“Imagine if we had found the first two or three occurrences of leafy spurge in the state and were able to get rid of it. Think of how much effort, money, headaches and time we could have saved,” Mealor commented. “Look at Canada thistle, Russian knapweed, salt cedar and the whole list of invasive species. What if we would have found those early? Finding these species early gives us a great opportunity.”

He continued, “I think we need to employ every tool we have to try to get a handle on these species.”

End game

Most importantly, with new invasive species creeping into the state, Mealor said, “We can’t be out all the time everywhere. Ranchers are our biggest asset in combatting these invasive species.”

With discussion on a management plan moving forward, he also notes that the working group is currently working on a survey to determine just how widespread ventenata grass and medusahead are in the state.

“Anyone who thinks they have medusahead or ventenata needs to call someone – weed and pest, conservation districts, me or Extension,” Mealor emphasized. “The opportunity we have to address this problem early before it gets too big is huge.”

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

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