Ventenata weed and wildfire

Cattleman Loren Stout examines ventenata, an invasive weed, growing in Oregon’s Blue Mountains near John Day. The species appears to benefit from wildfire, helping it spread.

JOHN DAY — Looking out at an expansive meadow in Oregon’s Blue Mountains, local cattleman Loren Stout sees not an idyllic landscape but an “environmental disaster.”

The problem is as subtle as it is pervasive: The wispy yellow grass drying in the sun isn’t forage that’s readily consumed by livestock and wildlife.

It’s ventenata, an invasive species that originated on the other side of the globe but now crowds out native plant life on large swaths of government-owned land in the Blue Mountains.

The weed contains enough silica — a compound traditionally used for glass production — that it’s largely considered inedible for herbivores.

“There is nothing utilizing this stuff,” said Stout. “It just looks lush in spring, but they won’t touch it.”

Aside from its lack of forage value, experts are finding that ventenata has another pernicious trait. Specifically, the invasive grass seems to benefit from the same wildfires that it helps fuel.

That dynamic has become especially apparent after fires ignited by lightning strikes in 2014 and 2015 that devastated tens of thousands of acres surrounding John Day.

“The invasion rate was reaching a level that it seemed to be affecting fire spread,” said Becky Kerns, a research ecologist with the U.S. Forest Service. “It doesn’t need fire to trigger an invasion, but fire may exacerbate and increase the population.”

Kerns is taking part in an interagency research project that’s studying ventenata’s influence on novel fire behavior, as well as mapping the extent of the weed’s spread and examining the role of climate change in that invasion.

The study began in 2016 in response to reports that ventenata was creating fuel connectivity across open scrubland, allowing flames to traverse sparsely vegetated areas that normally serve as fire breaks.

It’s expected that research papers from the study will first be published in 2020 though the overall project may last another year.

Ventenata appears to recolonize burned acres more quickly than native species, such as sagebrush, which provide important wildlife habitat, said Claire Tortorelli, an Oregon State University graduate student participating in the study.

“We’re not really seeing the recovery of those shrubs or woody perennials,” Tortorelli said.

Preliminary study results indicate perennial grasses are holding their own better than annual forage types, which haven’t been returning as readily after fires, she said.

Even though perennial grasses may have survived a fire, ventenata may impede their reseeding of the ground, she said.

“The concern is you’ll lose that perennial component in the long term,” said Kerns. “Invasive grasses tend to be pretty aggressive.”

An advantage the weed holds over many other plant species is its adaptability to land that normally has only scattered vegetation, said Tortorelli.

Ventenata is more abundant than these native plants and thus it contributes to the overall intensity of fires, she said.

“They’re not these super-productive ecosystems,” Tortorelli said. “When ventenata has invaded, there’s just so much more ventenata than anything else in that system.”

The invasive species is considered an “ecological driver” that’s capable of altering “ecosystems at landscape levels,” said Jessi Brunson, a botanist with the Malheur National Forest’s supervisor’s office.

“It can push the ecosystem over the edge, so to speak, into an environmental state from which it’s difficult to recover,” she said.

Because it’s now so widespread, however, ventenata falls into the “tolerate” category of weeds under the Forest Service’s classification system — the lowest priority for treatment, Brunson said. Other categories for weeds include “eradicate,” “control” and “contain.”

“The amount of herbicide and cost to control the species exceeds what we’re able to do,” both from the budget perspective and due to environmental study requirements, she said.

The interagency research currently being conducted is expected to help focus resources on areas where ventenata treatment will still be most effective, Brunson said.

Stout, the cattleman, blames the spread of ventenata on grazing restrictions that opened the region to medusa head rye — another invasive grass — and eventually led the way to ventenata.

“You have to take the competition away from these (desirable) annual grasses, and they do exactly the opposite,” Stout said, referring to federal and state land managers.

Kerns, the Forest Service research ecologist, said the interagency study has not established a link between grazing and ventenata prevalence.

It’s possible the weed’s behavior is varied across landscape types, such as prairies, forests and scablands, said Tortorelli, the OSU graduate student.

“In each of those community types, it’s going to have different impacts in relation to grazing,” she said.

New infestations of ventenata are best handled with the traditional “early detection, rapid response” approach to invasive weeds, Kerns said.

In the long term, a biocontrol agent — such as a predatory fungus, mite or other pathogen — may be discovered by USDA scientists studying the issue in Europe, ventenata’s homeland, she said.

Stout said he hopes land managers will react to the weed’s damaging influence before it grows irrevocably worse.

“It has to be done now,” he said. “This is do or die.”

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