Imagining A Future Without Invasive Annual Grasses

A helicopter whizzed over a group of 60 people standing in a sagebrush meadow outside of Sheridan, Wyoming, in July. Just a few meters from the ground, the helicopter’s hatch opened and a line of liquid rained down on the target: invasive annual grasses.

Although this particular helicopter was spraying water rather than herbicide as a workshop demonstration, it still wowed the people watching. Even more impressive? The nearby plot where invasive ventenata had been sprayed a couple years prior. Participants were amazed at the stark line between the treated and untreated pastures: on one side, healthy perennials provided forage for livestock and wildlife. On the other side, a monoculture of yellow invasive grasses was still degrading soil and habitat. 

This hands-on field workshop was part of a series of educational training events that empower people to combat invasive annual grasses in the western U.S. It was organized by a new Tech Transfer Partnership, led by the University of Wyoming’s Institute for Managing Annual Grasses Invading Natural Ecosystems (IMAGINE). Launched in 2022 by a team of interagency partners, IMAGINE’s Tech Transfer Partnership develops resources that transfer the latest technology and science on invasive grasses into action that conserves sagebrush rangelands. Working Lands For Wildlife is a founding member of the Tech Transfer Partnership and helped design content for this workshop series. 

“Invasive annual grasses are by far the leading cause of degradation in the sagebrush biome,” said Jeremy Maestas, ecologist and national sagebrush ecosystem specialist with the USDA Natural Resources Conservation Service. “Before now, we haven’t had a concerted proactive effort to tackle this problem at scale.”

Defending your community’s sagebrush core 

Invasive annual grasses, such as cheatgrass or ventenata, outcompete native plants and disrupt many parts of the ecosystem. They germinate earlier than native perennials, which allows them to siphon precious resources like water from native plants. They grow very quickly and die off earlier than native perennials, which means they are poor food sources for wildlife or livestock. Unfortunately, this also makes them flammable fuel sources that cause more frequent and more catastrophic wildfires.

The best way to address this biome-wide problem is to first protect intact core areas from being invaded. Next, grow these core areas by treating any emerging invasive annual grasses on the perimeter. 

The Tech Transfer’s Partnership’s three-part training workshops on invasive annual grasses are designed to take people from awareness to action. They provide support and hands-on resources for communities to create and launch an invasive annual grass management plan and start treatments on the ground.

“We learn best by doing. These workshops empower people to start thinking about how to strategically plan and manage the invasive grasses in their own communities,” said Claire Visconti, outreach coordinator and assistant research scientist for IMAGINE. 

In April, an introductory, or “Level One” workshop, was attended by more than 500 people nationwide. The Level Two field workshop in Sheridan built on these lessons by delving into the nitty-gritty “how to” of when, where and how to control the invasive annual grasses invading sagebrush country and getting to see examples in the field. Level Three workshops—which were held this last fall in Dillon, Montana, Cody, Wyoming and Gunnison, Colorado—are to provide specific resources for local working groups that are already managing invasive annual grasses.

“We take people from ‘defending the core’ to ‘defending your core’,” said Maestas. “We show participants how to bring in their own data and values to make a stand and protect their best sagebrush rangelands.”

New tools to tackle an old problem

In July, the 60 participants in Sheridan’s Level Two workshop talked through how to first determine the scale of the area: are you managing invasives in a pasture or an entire watershed? Next, they discussed how to inventory and monitor the field site. How much and where are the invasives? Are there any native plants left that can bounce back post-treatment? If not, how will you deal with restoring and replanting the bare ground once invasives are gone? All of these answers determine the types of strategies and tools each practitioner might use to control invasive annual grasses.

Out in the field, workshop participants were able to see what happens when you put the right tools in the right places. They saw the results of herbicide treatments, and were able to ask specific questions about how to practically apply treatments themselves.

“No one wants to spray herbicides more than they have to,” Maestas noted. “But in reality, it’s one of the only tools that works to break the cycle of annual grasses.” Luckily, new spatial technology that uses satellite imagery shows people exactly where herbicides can be surgically applied to most effectively defend and grow sagebrush core areas.

In the past, available herbicides only provide one or two years of control. Now, we have tools that provide longer lasting control by depleting the annual grass seedbank. For instance, spraying pre-emergent herbicides like Rejuvra have been shown to stop annuals from germinating in the soil for five years or more.

Native perennials like sagebrush, wildflowers, and bunchgrasses come back every year because their deep root systems survive in the soil over the winter. But invasive annual grasses die each year and must grow anew from seed in the spring. Using a pre-emergent herbicide allows native perennials to come back—but the annuals do not. 

“It comes down to: what do you want to save? Perennial grasses provide way better forage quality for livestock and wildlife, and they help keep the ecosystem intact,” Visconti said.

Seeing is believing

In Sheridan, workshop participants also heard from landowners about how treatment affected their cattle operation. “One rancher told us that aerial treatment vastly improved his forage production post-treatment,” Visconti reported. Another rancher told the group that he thought he could “graze his way out of the problem,” said Visconti, but it didn’t work. After aerial herbicide application, the rancher now has more native forage and doesn’t have to buy as much hay.

Plus, participants learned important lessons from an experienced aerial applicator, including the rate and timing of spraying. He recommended using a helicopter since they’re more maneuverable than a fixed-wing aircraft. 

The goal of IMAGINE’s Tech Transfer Partnership and its educational resources is to “build a cadre of people around the biome doing this kind of work so we have core areas that stand a chance of avoiding invasion in the future,” Maestas said. 

Workshops like the one in Sheridan build people’s confidence in how to use management tools to restore their own rangelands. This in turn builds a cadre of people around the West who are dedicated to halting the invasion of annual grasses and conserving the sagebrush biome. 

IMAGINE is hosting another virtual Level One workshop in the spring of 2025 and organizing two more field workshops next summer in Idaho and Nevada. 

“What’s really exciting is that this stuff works when it’s done right. We’re seeing amazing results with a healthy understory coming back,” Maestas said. “Seeing is believing. And believing inspires more people to do it themselves.”