Cheatgrass, the invasive weed that sticks in socks and shoelaces, finds its way into dog ears and has disrupted wildlife by taking over native grass and brush habitats across the arid West, might have a new foe.
A researcher at Washington State University has identified a native soil bacteria that inhibits the growth of the weed when nurtured to high levels. Its discovery is making land and wildlife managers hopeful they might soon have a new weapon to battle the Eurasian invader that is spreading at a rate of 1,000 acres per day.
“This is really promising. If this works, this potentially will give us a new tool to re-establish perennial vegetation,” said Alan Sands, of Boise and owner of Sage Wildlife Consultation Service.
Cheatgrass thrives by growing later in the fall and earlier in the spring than native grasses. But when it dries in the heat of summer, it fuels high-intensity and fast-moving wildfires that are blamed for wiping out sagebrush habitat, a leading cause of the demise of sage grouse. It also out-competes native bunch grasses that are important for several wildlife species, including elk and deer.
Ann C. Kennedy, a soil microbiologist with the U.S. Department of Agricultural Research Service at WSU, discovered the bacteria after working with a team that identified organisms that inhibit the growth of winter wheat. Kennedy wondered if she might be able to find something that did the same thing to weeds. She started examining the soil, where she found pockets of naturally stunted cheatgrass and was eventually able to isolate bacteria that was responsible for the depressed growth.
She and others then tested the organisms to make sure they were not harmful to crops or native plants.
“After a long series of tests, we found a group of these organisms that are inhibitors to cheatgrass, medusa head and jointed goat grass,” she said.
In further testing, Kennedy was able to depress cheatgrass growth by applying high levels of the bacteria to test plots infested with the weed. The bacteria, known as ACK55, inhibits the growth of roots and the production of seeds. Over time, the cheatgrass is knocked back.
“In the first year, we see maybe a 20 percent reduction. The next year in the spring we see 40 percent and then 50 percent and 60 percent,” she said. “In about five or six years there is hardly any cheatgrass left.
We are down to near-zero cheatgrass per square foot.”
That slow but progressive reduction is critical. Many land managers worry that the development of successful weed treatments will simply open up ground and pave the way for another invader. But the slow reduction gives native plants time to re-establish either through existing seeds in the soil, or by replanting by land managers.
“Over the course of three to five years, the bacteria finds almost all the seed, and they slowly, slowly leave the site, which is the perfect process for the natives to reclaim the site in a slow progression that is more natural,” said Fred Wetzel, the national wildland fire and emergency response adviser for the U.S. Fish and Wildlife Service.
Wetzel said it might be possible to coat the seeds of native plants with the bacteria so it can be spread at the same time as the seeds. The bacterial might also be applied simply by mixing it with water and spraying it from aircraft or making it into pellets that will melt into the ground following rain.
Wetzel said the bacteria can be cheaply grown and stored.
“I hesitate to say how cheap it is,” he said. “It’s is unimaginably cheap to grow the bacteria. You can put the bacteria in a mason jar and fill it half way up with water and that is the amount of bacteria you put on an acre.”
But before that happens, the bacteria will have to be approved for use as a weed treatment by the Environmental Protection Agency. Kennedy and her colleagues have permits to test it on 10-acre plots and are working to get permission to test it on a larger scale. Wetzel estimates it will likely be at least two years before it is ready to be used as a land management tool on a large scale.
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