The economic impacts of Medusahead rye can be extreme. Dense infestations can reduce rangeland livestock carrying capacity by 50-80%. The resulting impact on wildlife habitat, and the increase in wildfire frequency and severity causes additional losses to ranchers and rural communities. Meanwhile, it is so resilient, that controlling it with herbicides can cost as much as $2,000 per acre and reseeding can be cost prohibitive. So this discovery by a rancher impacted by this invasive grass is very important to any community or landscape it threatens.
A team of researchers from Utah State University and the Agricultural Research Service has been studying how to control medusahead rye with grazing. When they started, they knew that medusahead is mostly stem with a few small leaves, its seedheads have nasty awns, it is high in silica and low in nutrients and it produces a thatch that smothers other plants, doesn’t readily breakdown, and is highly flammable. They also had decades of research behind them on how animals choose what to eat based on what they learn from their mothers, and on the nutritional value of a plant. Their goal was to find a way, based on what they knew about medusahead and how animals choose forages, to increase the amount of medusahead cattle and sheep grazed in pasture.
They looked at timing of grazing to see if it was the awns that prevented animals from grazing the plant. It wasn’t. They tried providing high energy supplements so that animals would be better able to process the dry thatch, but most of the supplements didn’t help. Canola meal, the only supplement that showed promise was expensive and impractical to feed on rangelands. Early experience grazing the plant alongside mom made no difference, and it was impossible to force animals to eat the grass.
They learned that when medusahead was 10% of the plant community, the amount of medusahead in sheep diets was also about 10%, suggesting that proper grazing in areas with low levels of medusahead were not likely to increase its spread. They also learned that cows, who are better at digesting grasses that are high in fiber and silica, were better medusahead eaters than sheep. (You can read their short report here.)
They were at a loss until they heard from Luke Mcrae.
Mcrae is a Rtizville, Washington rancher who runs cattle on the Channeled Scablands, a region of coulees, flat plateaus and steep canyon sides. It’s a beautiful area with one big problem: Medusahead rye. It’s a near monoculture in some places and ranchers have had to reduce stocking rates by 50%.
In 2014, Mcrae sprayed his fencelines before turning his cows out and he noticed his cattle spent a lot of time grazing where he had sprayed medusahead. Apparently, spraying glyphosate (Roundup) on medusahead before boot stage dramatically increases its palatability. He shared his discovery with the researchers at Utah State University and the Agricultural Research Services Poisonous Plants lab. Based on his observations, they ran trials to see how glyphosate worked, what the impact on the larger plant community might be, and how they might use this information to begin managing medusahead with grazing.
One of the first trials on glyphosate was conducted by USU graduate student, Casey Spackman. In the study, he set up three plots:
1) glyphosate with potassium salt (Roundup RT3) at a rate of 154 g ae/acre or 0.35 lbs ae/acre
2) potassium chloride (KCl; salt in Roundup RT3) at a rate of 0.15 lbs/acre
3) Control (CTRL, no chemical application).
Average medusahead density in the plots was 34%. Spackman sprayed it in boot stage just before seedhead emergence.
From their 2016 Research Report, here’s what they learned:
“From June 14 to June 18, the percentage of bites taken from medusahead in five minutes increased from 7 to 31% of total bites, while the percentage of bites taken of other grasses declined from 77% to 56%. The percentage of bites of forbs remained fairly constant (16 to 13% of bites) throughout the trial. The abundant perennial bunchgrasses in the plots likely decreased consumption of herbicide-treated medusahead.”
The salt content of treatment 2, did not increase preference for medusahead. In fact, cattle tended to avoid that strip. Meanwhile, in the Roundup RT3 sprayed strips, medusahead biomass declined by 61%, and by 40.6% in the control strips.
What is the Impact on the Overall Plant Community?
Because of the timing of the application of Roundup RT3 and the dilute mixture used, other plants in the pastures do not seem to have been affected. In fact, the application of Roundup may increase tillering of bunch grasses. Check out these photos from the trials.
What Does This Mean for the Future of Medusahead?
Researchers found that Glyphosate (Roundup RT3) application increases cattle preference for medusahead, but they’re not yet sure why. When I spoke with Beth Burritt, she said that one theory is that glyphosate applied at this stage of the plant’s growth may prevent it from setting it’s silica armor that has done so well preventing animals from grazing it. With her colleagues, she says that because it increases grazing of medusahead while allowing other plants to thrive, this could be part of an integrated approach of herbicide and grazing is an efficient tool to control medusahead spread on rangelands.
The team has conducted other studies using herbicides to increase consumption of medusahead. We will update you as that information becomes available.
Big thanks to Beth Burritt for sharing her Powerpoint and the fact sheets associated with her work and for talking with me about it all. She asked that I remind On Pasture readers that if you see something, say something to researchers like her. Like Luke Mcrae’s observations, what you’re seeing could be an important part of advances for everyone.