Range officials fight two new invasive species

Range officials fight two new invasive species


At first glance, to the untrained eye, ventenata looks like just another invasive annual grass. It’s about a foot tall and cures to a golden brown color.

That’s why Doug Masters didn’t initially worry when he saw some on his ranch in Sheridan County.

Then in 2016, a researcher with the Natural Resources Conservation Service told him the bad news: The new grass on his land bordering Montana was one of the worst invasive annual grasses to reach the Great Plains.

Not long after, experts found another invasive grass – medusahead – on another piece of land he grazed. Left unchecked, the two grasses could spread to make at least two-thirds if not more of his range unusable to animals from cattle and mule deer to sage grouse and songbirds.

“Worst-case scenario is they become extensively established in the Great Plains,” said Andrew Cassiday, a district conservationist with the NRCS in Sheridan. “We stand to lose a great deal in terms of wildfire potential, in terms of wildlife habitat, in terms of rangeland and pastureland grazing resources. All of those are in great peril.”

In a West that has dealt with cheatgrass for more than a century, the advent of these two new grasses is instilling fear in everyone from ranchers to wildlife biologists. Battling them should be like fighting a wildfire, Cassiday argues. Experts need to make a plan and execute before it’s too late.


Range ecologists don’t know exactly how or when ventenata and medusahead arrived on U.S. soil. They’re from eastern Europe and southwestern Asia, and have been a problem in Oregon, Idaho and Washington for years.

A University of Wyoming graduate student first identified ventenata in 2016 on a ranch in Sheridan County. From there, experts discovered it throughout the western portion of the county and, three years later, have found it in even more locations from the foothills of the Bighorns into Campbell County and throughout Montana down to Interstate 90.

“The few years we did watch it, the population grew and took over more and more acres every year,” Masters said.

Experts found medusahead later that same summer.

For Luke Sander, supervisor of Sheridan County Weed and Pest, it was a worst-case scenario. Cheatgrass has been bad enough – it grows in disturbed areas like pasture overgrazed by cattle or blackened by fire – but at least it offers some bit of nutrition to wildlife and livestock in the early spring.

Medusahead and ventenata have no nutritional value. They also take over every bit of landscape.

“If you take any good you can get from cheatgrass away, you get ventenata,” said Brian Mealor, an UW associate professor and director of the Sheridan research and extension center.

Their seeds are so high in silica – a mineral compound used to make glass – that animals refuse to eat it.

Like cheatgrass, they are an annual grass that reproduces by seed in the fall. They grow in thick bunches and their seeds burrow down to the ground before snow, planting roots, sprouting and even growing at times under snow throughout the winter. When snow melts and the sun appears, they use any moisture and nutrients in the ground, effectively choking out native grasses.

And then each plant produces hundreds of seeds that can live for years.

The grass dries quickly in the middle of summer, creating a thick fire-prone mat, allowing blazes to rip across the prairie, killing sagebrush and other native plants, leaving behind soil ripe for more medusahead and ventenata.

“They dramatically deteriorate critical wildlife habitat across the board, whether you’re talking about mule deer and elk to anything that benefits from sagebrush communities. It’s, I think, an even further degradation than cheatgrass,” Mealor said. “The weed scientists I’ve talked to said they would trade every acre of medusahead and ventenata to have cheatgrass back. It’s hyperbole, but illustrates the level of forage quality.”


Shortly after both species were discovered, anyone with any involvement in weeds including the NRCS, Weed and Pest, the University of Wyoming, U.S. Fish and Wildlife Service and individual landowners formed a working group to create a plan.

Ventenata, the plant most similar to cheatgrass, has spread so quickly through northeast Wyoming that experts are focused mostly on containing it within the area and not allowing it to spread further. Medusahead, the worse of the two invasive species, has only been found in select areas of Sheridan County. With targeted efforts, Cassiday and Sander believe they could keep medusahead largely at bay.

The best way to fight the two species is with herbicides sprayed from the air. They’ve had some success with a relatively new chemical called Esplanade. It kills all annual grasses and their seeds. With luck, two consecutive treatments could result in a diminished presence of the weed and even localized eradication, Cassiday said.

But spraying is expensive. Some money is available from state and federal agencies, but landowners still must decide if they can afford to spray on top of their other expenses, said Masters.

“If we can have the rest of the neighbors signed onto the program we can do large blocks of it,” Masters said. “It will be a battle we live with for the rest of our lives, or at least the rest of my life.”

The results from early spraying are striking, Sander said. In areas that were sprayed the native grasses come back thick because of the nutrients and water suddenly available in the absence of the invasives.

Medusahead and ventenata will continue to be part of a regional and state dialogue. Gov. Mark Gordon recently formed an invasive species working group with a policy-focused task force and a science-based one.

“We’re implementing every best-known management practice that exists,” Mealor said. “And we’re inventing some of our own as we go.”


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