Weed & Pest
Cheatgrass transforms ecosystems in Wyo
Torrington – “There’s a lot of demand to figuring out how to best and most effectively manage cheatgrass in Wyoming,” states University of Wyoming’s (UW) Extension Weed Specialist Brian Mealor.
“Last fall, we had good moisture levels. That’s one of the reasons why cheatgrass is so abundant and doing so well this year,” explains Mealor.
He adds, “Cheatgrass is really easy to kill. It’s an annual. Pull it up and it’s dead, but it’s really hard to get rid of.”
Cheatgrass is a winter annual grass but has the flexibility to have multiple germinations in the fall, spring and summer. Typically cheatgrass germinates in the fall and overwinters as a seedling, where it is able to kick-start its growth and mature before any other perennial grasses.
The hearty plant is able to withstand cold temperatures and will turn purple when it is about to dry up and go dormant.
“Almost all of our native plants are completely shutdown at freezing, but cheatgrass is able to elongate its roots and germinate a little above 32 degrees Fahrenheit,” notes Mealor. “That’s one of the reasons it’s problematic.”
“Cheatgrass at a high density is highly competitive. Seed production is the only way cheatgrass grows from year to year,” states Mealor. “It has been documented cheatgrass can produce up to 500 pounds of seed per acre.”
Cheatgrass is considered an ecosystem transformer because it changes the way ecosystems work. The invasive grass suppresses the growth of native species and perennial grasses when it grows at high densities, leading to a loss of biological differences of plants.
Cheatgrass can also become an extreme fire hazard when it dries out.
“A high production of cheatgrass can burn very hot, and this is one of the reasons we’re seeing increased fire frequency and increased fire intensity across the western U.S.,” comments Mealor.
He continues, “This gives us another level of challenge dealing with cheatgrass, especially when we are trying to maintain sagebrush ecosystems for wildlife habitat.”
Fire can be used as a method to control cheatgrass, but it is most effective when the seeds are in the air instead of on or in the ground.
“Fire typically doesn’t reach a high enough temperature to kill seeds when they are already in the ground,” comments Mealor. “Most reports indicate around 90 percent of cheatgrass seeds germinate within one year and viability of those seeds can be up to eight to 11 years.”
By preventing seed production of cheatgrass for three years, the soil seed bank might be depleted and keep cheatgrass from becoming established, notes Mealor.
However, cheatgrass thrives when there is free nitrogen in the soil and is often times made worse after a field has been burned.
“Prevention is really our highest leverage strategy against cheatgrass because if there is no cheatgrass onsite, we don’t have to worry about control,” states Mealor. “For very small populations of cheatgrass, producers might want to think about eradicating the population.”
Mealor notes unsuccessful long-term management of cheatgrass could unfortunately lead producers to considering abandoning their property.
“Herbicide has been the most consistent positive result we’ve seen for cheatgrass control,” he says. “However, we recommend to start an assessment of the cheatgrass invasion to know what the recovery potential is for the ground, then go from there.”
“When doing any type of reseeding, don’t pull the plug until after three years because sometimes it takes that long, especially for native species, to come up and be established,” claims Mealor.
Crested wheat grass, western wild rye and pubescent wheatgrasses compete very well with cheatgrass, but the societal push is away from introduced species towards native species, mentions Mealor.
Mealor spoke at the cheatgrass workshop held in Torrington on June 11. The workshop included discussions of cheatgrass management practices and a tour of the UW Sustainable Agriculture Research and Extension Center (SAREC) to look at the test plots of cheatgrass.
While the herbicide Plateau has been noted as the most effective way to kill cheatgrass, promising new bio-control research of using a Pseudomonas bacterium to target cheatgrass roots is being conducted in Converse and Goshen counties.
Converse County Weed and Pest District Supervisor Cheryl Schwartzkopf conducted tests using the cheatgrass bacteria in October 2013.
“We apply the cheatgrass bacteria during October to November,” says Schwartzkopf. “For this bacteria to work, there needs to be some moisture to help incorporate it into the ground and for it to take effect against the roots of cheatgrass.”
Sunlight kills the bacteria, and it must remain frozen until it is mixed with water or a mixture of water and herbicide when it is applied to infested cheatgrass fields. Ten grams of the concentrated bacteria is needed for every five acres.
“Bio-control is a very slow process. It takes about three years to completely take affect against the cheatgrass,” she says.
She adds there has been a decrease in the amount of cheatgrass on her test fields, but more time is needed to see the full effect the bacteria can have on cheatgrass.
The cheatgrass bacteria are already present in Wyoming’s soils but are not concentrated enough to have an effect on and kill cheatgrass.
Schwartzkopf notes the bacteria remains in the location where it is applied and will not migrate. The bacteria will not suppress any crops or native plants and can only take effect on cheatgrass after it has germinated. It also can have an effect on jointed goat grass and medusahead.
“The lifespan of the bacteria is dependent on the amount of cheatgrass. If there aren’t any cheatgrass roots for it to feed on, it will reduce back to the natural carrying capacity for that site,” comments Schwartzkopf.