MSU Graduate Student Works to Understand, Control Invasive Grass on Crow Reservation

by Brett McRae

BOZEMAN — For the past decade, Ventenata dubia, an invasive grass, has popped up across 24 counties in Montana, where it has decreased plant diversity and lowered forage availability for livestock and wildlife.

With the grass beginning to invade land in his home on the Crow Reservation, Zach Fighter, a graduate student in Montana State University’s Department of Land Resources and Environmental Sciences in the College of Agriculture, saw a subject for his master’s research project.

“It’s starting to become serious, and I don’t think a lot of people knew it was there because they didn’t even know what the grass was,” said Fighter, who is from Pryor and an enrolled tribal member. “It could potentially take over and invade your pasture and take away your desirable species, what your livestock wants to eat, and by displacing that, you’re not going to get good forage value and lose money.”

Fighter works alongside co-advisers Jane Mangold and Scott Powell on the Crow Reservation exploring ways to remediate ventenata through chemical control and remote sensing.

Fighter’s research is funded through a grant from the Montana Noxious Weed Trust Fund. The research team is collaborating with others from the Bureau of Indian Affairs, Big Horn County and the University of Montana. Fighter is also a part of the Sloan Indigenous Graduate Partnership, a scholarship program that supports Indigenous graduate students pursuing degrees in science, technology, engineering or mathematics with the intent of increasing the number of Indigenous Americans earning master’s and doctoral degrees in STEM disciplines.

In researching chemical controls for ventenata, the team is using two different herbicides, indaziflam and imazapic. The former is applied before ventenata germinates, while the latter is applied after germination. Fighter applied indaziflam in August 2021 and imazapic in November 2021 and will assess the results this summer to see how well those treatments controlled the grass. Along with the herbicides, Fighter is looking into a soil amendment that could control the grass by adding micro-nutrients that encourage desirable species to grow.

Fighter has four research sites, two near Pryor, one near Lodge Grass and another east of Crow Agency. Each 10-by-60-foot plot of land is split so that each treatment has its own area, giving Fighter a better understanding of which controls are working at which rates.

Just as important as understanding which herbicide is more successful is the application method. Fighter is using high and low water carrier rates. High rates mimic ground application and low rates mimic aerial application. Ground applications involve the use of ATVs or walking the property and use 15 gallons of water per acre. Aerial applications, however, only use 5 gallons per acre and can be administered by helicopter or plane, making it easier to cover larger swaths of land like those found on the Crow Reservation.

“The Crow Reservation is one of the hot spots of ventenata in the state,” said Mangold, invasive plant specialist for MSU Extension and a professor in LRES. She has been researching the grass since 2015, but this is her first time researching its presence on the reservation. “Other places I’ve seen ventenata growing in smaller, isolated patches. But the ventenata I’ve seen on the reservation and down into Wyoming is more ubiquitous across the landscape.”

Ventenata is a winter annual grass with an open and airy inflorescence. Stems have a stiff, wiry texture. Its leaves are rolled lengthwise or folded, and its roots are shallow, about 1 to 2 inches deep.

To measure the effectiveness of the chemical controls, Fighter will use various remote sensing tools to collect data on the health and vigor of plants. Powell, a professor in LRES, specializes in remote sensing and spatial analysis to measure vegetation. He said the data they will collect is based on how much light the plants reflect, including visible and non-visible light, such as near-infrared.

“The difference between a healthy plant and a nonhealthy plant in the near-infrared spectrum is really pronounced,” Powell said. “You can develop indices like a remote sensing vegetative index, that allows you to track the health of the plant after it’s been sprayed with herbicides.”

Both Mangold and Powell said Fighter soaks up as much information as he can and is effective at discussing difficult topics with constituents.

“We met with the Big Horn County Weed District, and Zach led the whole conversation. Scott and I were there, but it was more about Zach and you see him interact with people and he’s really good at it,” Mangold said. “He is taking in information and has a way of processing it and putting it into practice. You can especially see that when he interacts with the local community members on the reservation.”

Fighter received his bachelor’s degree in rangeland ecology and management from MSU in 2017. He said he was always interested in invasive species, and when he decided to continue his education, it made sense for him to specialize and enter the LRES program to build off his rangeland knowledge.

Fighter expects to graduate in December 2022 and hopes to continue his career in invasive species ideally with the Bureau of Indian Affairs office in Billings.

“It’s been good to know that I can potentially help land managers and landowners and provide new information on this species,” Fighter said. “I am interested to see how my controls work and if they work great this summer, I can provide land managers and owners with vital information to start using on their land right away.” 


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