Soil bacteria, fungi studied for potential cheatgrass control in WyomingWritten by Natasha Wheeler
Riverton – “Cheatgrass is an annual grass that is wreaking havoc over the entire western United States, causing millions of acres to become degraded,” noted Fremont County Weed and Pest Supervisor Aaron Foster at the Wyoming Association of Conservation Districts (WACD) Area IV Meeting in Riverton on Sept. 3.
Cheatgrass is an invasive weed that alters the successional changes of sage steppe communities, decreases biodiversity and changes the structure and function of rangelands.
“In Wyoming, we are lucky. We are not nearly as impacted as the Great Basin and the sagebrush steppe regions further west of us. We have a potential opportunity to get cheatgrass in check,” Foster commented.
Currently, there are limited options for eliminating the weed, and land managers are searching for new solutions.
“We could really use some other tools in the toolbox for managing cheatgrass,” he stated.
One potential tool may be the use of biocontrol – the use of organisms, such as bacteria, insects or other species, that will drive out the undesirable grasses.
“One biocontrol option that is probably closest to becoming something we can use is a naturally occurring soil bacteria. A strain has been isolated to specifically target cheatgrass,” Foster explained.
The bacterium reduces cheatgrass root elongation, which reduces the vigor and growth of the plant, causing it to be less competitive with other species.
“It also reduces the amount of seed load that comes from cheatgrass in the area. With enough reduction over time, it might allow desirables to come back,” he continued.
Foster believes that the bacteria will be available as a product this fall, marketed as a biological soil amendment.
“The Environmental Protection Agency (EPA) hasn’t gotten through the approval process yet to market it as a bio-pesticide,” he noted.
EPA approval for pesticide status will affect product labeling and how it can be used to manage cheatgrass.
“Hopefully, with pesticide labeling, we can use the product on a large scale,” he commented.
Biowest Ag Solutions, a company in Idaho, is producing the product to be sold in one gallon per acre application rates at an estimated eight dollars per gallon.
“The drawback right now is that they are only going to make it available in a minimum of 250 gallon totes,” Foster mentioned. “We also want to use it quickly. We can’t put it in storage like some other products because the bacteria will die.”
Application of the product also introduces some challenges. The manufacturer recommends application when the air temperature is less than 50 degrees.
“Aerial applicators don’t want to fly when it’s less that 40 degrees because they have freeze issues. We have a narrow window between 40 and 50 degrees on a day with no wind,” Foster explained.
It is also important to incorporate the bacteria into the soil as quickly as possible since UV light destroys them in a short period of time.
“We really want it to rain or snow as soon as possible after we apply the product to get it into the soil,” he said.
Once the product is applied, it takes a number of years for results to appear.
“It takes two or three years to see progress or impact on cheatgrass. The first year, the area will look pretty much the same, so we have to give it some time,” Foster commented.
Also, other herbicides can be used in combination with the bacteria application to manage cheatgrass areas.
“Another one of the biocontrol options that may also come about for cheatgrass management is a combination of four fungi,” Foster added.
Each of the four types of fungi attacks a different component of the cheatgrass, from dormant seeds to germinating seeds and young plants.
“The hypothesis is that there is a complex interaction between microorganisms in the soil and the fungi, related to a carbon influx in the soil,” he explained.
Although a predictable pattern has not yet been seen, areas of the Great Basin and Utah are experiencing mass cheatgrass die-offs in areas where the specific fungi are found.
“If we can learn to predict the die-offs, maybe we can be there in those areas to reseed with native grasses,” Foster noted.
He explained that cheatgrass control will likely require incorporating biocontrol, herbicides and land management practices to eliminate the weed.
“With these bicontrol options, we have more tools in the toolbox, which means we have more integrated programs which will hopefully increase our likelihood of success,” he said.