Considerations for cheatgrass management
January 21, 2013
Cheatgrass is a highly downy broam, cool season annual grass with relatively short seed longevity that has been poking itself into western landscapes for decades. Management of the highly invasive and generally unwelcome grass continues to challenge producers, who flocked to University of Wyoming College of Agriculture Professor and Extension Weed Specialist Brian Mealor's cheatgrass control presentation at the Wyoming Natural Resource Rendezvous in Casper, WY, on Dec. 10.
"If there is one message to take home from this presentation, it's that cheatgrass is more than just a standard weed problem – we're thinking about managing a system, not just killing a weed," explained Mealor of the big picture.
He continued, saying the good news is that cheatgrass is relatively easy to kill, and the bad news is it will not be possible to completely remove it from western landscapes.
"I realize that sounds a little counter intuitive. As an individual plant, and group of small plans, it is relatively easy to kill. But, it's difficult to remove from the ecosystem, and to remove its impact from the ecosystem,"Mealor further explained of his opening statement.
Furthermore, Mealor pointed out that cheatgrass seed has a relatively short viability time-frame of between three and 11 years. Depletion of seeds in the soil is a key target in managing the grass long-term. However, seeds given the opportunity to grow during their viable years can do so in a variety of soils and environmental conditions, adding to the challenge of managing the species.
Fire also gives cheatgrass an advantage, and Mealor encouraged attendees to document where the grass is present on their operations today to aid in post-fire management that could occur starting tomorrow.
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"If you don't know where it was prior to fire, it will be difficult to know where to treat in the lag phase before cheatgrass comes back," he explained of his reasoning.
Where cheatgrass is present but not dominant, the key is preventing it from moving that landscape over an ecological threshold, where it becomes the new dominant within the system. Once that occurs, it becomes much more difficult to return to a more desirable and varied plant system.
"From an ecological standpoint, when that threshold is near, we need to ask if it makes more sense to implement aggressive management at that point to keep the system from changing, and identify things we want to keep on site as we implement management. If you want to keep Sagebrush as a functioning part of the system, for example, fire is probably not the best option. We can alter our management in a way that keeps what you want as a functioning part of the system," explained Mealor.
In areas that appear to be 100 percent cheatgrass, he suggested taking time to look around to see if there is something else present.
"Sometimes when digging through cheatgrass patches, you'll see under the canopy and around the ground that there is other stuff growing, and it's just being suppressed by the cheatgrass. It's good to see if there is something in there to recover, and that may allow you to prevent things from looking like a parking lot if you do get good control of the cheatgrass," stated Mealor.
After determining the severity of the problem, looking at treatment options is the next step.
"Grazing cheatgrass is one relatively complex option. Yes, the plant does provide some kind of forage. Yes, it is relatively nutritious, and has a high palatability early in the year. But, once it starts to go to seed and change color, for the most part livestock leave it alone. Timing is a big issue – being there at the right time to do maximum damage to the cheatgrass while also getting use out of it, then getting out of there early enough that you're not damaging the other cool season grasses is critical," explained Mealor of effective grazing management to control cheatgrass.
An intensive stocking rate for the short window of ideal cheatgrass grazing is also ideal, and can be difficult to implement in the big pastures seen in many parts of the west. However, when grazing is utilized correctly, it can have a significant, positive impact on the landscape. Plus, it is often the most affordable and practical management choice.
Going forward, Mealor explained that one project in the works will look at ground litter, which facilitates cheatgrass emergence and establishment, and grazing. The idea is to utilize grazing to manage litter, and potentially reduce total cheatgrass emergence and establishment over time.
"Chemical control is another option. Right now there are about six or seven rangeland and pasture land labeled herbicides with cheatgrass specifically mentioned on the label. Roundup, Plateau, Journey and Matrix are a few examples. I've used them all and I've seen them all work really well sometimes, and not work well at all sometimes, and it's that variable that concerns people" explained Mealor.
Based on Mealor's multiple chemical control studies, he said the answer to the question of if you can remove a grass weed from a grass system without killing everything, is yes, for the short term.
"In one study, two years after treating with Plateau, Matrix and another herbicide, we saw different mixes of forage grasses, some decent forbs, and almost 95 percent cheatgrass control," stated Mealor.
He continued, stating that in almost all treatment experiments, completed pre-emergence in the fall, there was a 16-fold reduction in cheatgrass, and a seven-fold increase in perennial grass production. But, those results don't stick, and some degree of reinvasion is common within two-three years of a chemical treatment, with complete reinvasion generally occurring in four years.
"We can't treat once and walk away; we have to be committed to treating over the long-term. We also need to prioritize our efforts, and treat areas that are more important from a wildlife standpoint, and areas where we think we can get a bigger benefit from a forage production standpoint," he stated.
Going forward, Mealor said that a number of partners will be working on a prioritization strategy of how to most effectively deploy resources across the landscape to manage cheatgrass.
"Our cheatgrass management mind-set for the most part in the west, at this point in time, seems be that if we could control it long enough to allow desirable perennial growth, reestablishment, or recovery, then we might be able to reduce its impacts over the long-term," concluded Mealor.