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IMAGINE controlling invasive annual grasses

Attendees learn about aerial herbicide application for annual grass control at a field tour in 2019. | Photo courtesy Uninversity of Wyoming, IMAGINE.
IMAGINE UW

Ventenata will make you wish for cheatgrass. That’s the sentiment of landowners and managers who are dealing with the invasive, introduced grass. Ventenata was first identified in Wyoming–anywhere east of the Rockies, actually–less than 10 years ago, but researchers and land managers recognize the importance of control and are creating partnerships to reduce the impact of yet another invasive annual grass on the ecosystem. 

A number of introduced annual grasses, like ventenata, cheatgrass and Medusahead, are the target of a new coalition of researchers, public land managers and private landowners.  

The Institute for Managing Annual Grasses Invading Natural Ecosystems (IMAGINE), centered at the University of Wyoming, is taking a backward approach to research. They’re gathering data from the management techniques on the ground, and correlating that, developing hypothesis and then studying further.  



Brian Mealor, director of University of Wyoming’s Sheridan Research and Extension Center, and the IMAGINE program, said the goal is to provide practical, effective solutions to land managers. “It helps give them some data and information on how well their management objectives are working, and moves them toward their goals for vegetation,” Mealor said. “On the flip side, we have those data across a larger expanse of rangelands.” 

From there, they can look more closely at how the grasses may respond to herbicides, given different soil types or starting conditions, for instance.  



“From the research standpoint that really sort of flips the lens,” he says. “It also gives us more power to be predictive and understand patterns across the landscape, and to help landowners make decisions across the landscape.”  

David and Terri Kane ranch near Sheridan. David is the fourth generation of his family on the ranch. One of their ranches was among the first in Wyoming to identify ventenata, in 2017, and is part of the group involved with IMAGINE.  

They were also one of the first to use an aerial-applied herbicide, Rejuvra, which was originally developed for cheatgrass. The herbicide is a pre-emergent, so it acts on the seeds, killing the annual grasses as they germinate.  

Ventenata germinates in the fall, so that’s when they spray, ahead of the estimated germination date. The goal is to eliminate the seedbank, which early research suggested would take about four years.  

Based on what Kanes have seen on their ranch, the Rejuvra worked for about three years on the ventenata.  

“They were thinking they could spray in year one, and go back in year four, and maybe year 10, they’d be done. We had to go back in year three,” Kane said.  

That information is a huge help to managing invasive species on a larger scale, Mealor said.  

“This research is co-produced or co-created. It just means we’re working in partnership to answer questions together. That’s how our program has worked for years, but the scale and magnitude of what we’re doing with those partners has dramatically changed.”  

The introduction of venetenata and Medusahead made researchers and land managers realize how important it is to be proactive in addressing these invasive species.  

Kane said they identified ventenata one year, and the next year, nearly their whole ranch was covered with the grass. The grass seeds similar to cheatgrass, but has a high silica content, making it nearly impossible for any animal–wildlife or domestic–to use for forage. “There’s never a time that it’s palatable for grazing,” Kane said. That makes it a concern for both ranchers and public land managers for whom wildlife is the highest priority.   

The information like they gathered on the Kane ranch is added to what they know about annual grasses and herbicides in general.  

Kane said the first year after applying the herbicide, which targets seeds only, not affecting perennial grasses and forbs, it was almost like the range had been fertilized. “It was hardy and healthy and very vigorous,” he said. 

Mealor said the more desirable perennials, that hold their nutrient value longer, stay green longer and are generally higher quality forage, take advantage of the extra moisture freed up by killing off the early-growing annual grasses. It not only improves the range immediately, it sets it up to be more stable and resilient during a drought.  

Ventenata affects rangeland to such an extent that ranchers would have to choose between controlling it with herbicides–an expensive proposition–and buying supplemental feed, Mealor said.  

As Kane points out, “The cheapest land you can buy is your own. With noxious weeds, you can only bury your head in the sand for so long. Something’s gotta give. They’re going to dominate. Even though it’s so expensive to spray, it’s more cost-effective than not spraying. If you can’t afford to manage the land, you probably can’t afford to own it–public or private.”  

Those who neighbor with public lands, or who are responsible for managing public lands, are familiar with another major challenge, public perception.  

“IMAGINE has had a huge hand in improving the relationships between landowners and public agencies, ” Kane said. “It’s helping the federal agencies realize and understand it is a problem, and being responsible for taking care of it. It gives them the tools to help them figure out how best to manage it, and to use to educate the public about what they’re doing, and why.”  

That education and awareness is vital for slowing the spread of invasive species that don’t respect property boundaries.  

Mealor hopes this program becomes a prototype for implementing partnerships across other natural resource management segments. “The principles and framework we’re setting up, this cooperative research could be used for any natural resource issue that crosses boundaries.” And not just property boundaries. “We pretty regularly communicate with folks in Montana, South Dakota, Nebraska, just trying to get people sort of rowing the boat in the same direction,” he said.  

Mealor is also facilitating relationships with people who are not typically part of land management discussions, like soil microbiologists and economists, trying to put together a picture of the broader-reaching impacts of management decisions.  

An example he uses is of an area where they’ve done a lot of aerial treatments for annual grasses, where a different organization is studying mule deer, with GPS collars. “We’re using their location information to see if they respond to where these annual grass treatments occurred, to see if they treat it differently,” Mealor said. “That’s the kind of stuff we don’t know. We can go clip grass and measure protein all day, but now we can figure out how wildlife or livestock respond to the management techniques.”