A new weapon against an invader being tested near Lake Lowell

Naturally occurring bacteria are being used on cheatgrass.

cmsewell@idahostatesman.comJuly 30, 2013 


    Cheatgrass, officially named Bromus tectorum, is also called downy brome. It arrived in the United States in the late 1800s, likely from grain shipments from Europe and Asia.

    It's now found from Alaska to Mexico but thrives in the West's arid grasslands and sagebrush steppe.

    Because it is a winter annual able to germinate in fall or spring, it is one of the first plants up in the spring, giving it a competitive advantage over native plants. Cheatgrass also has a short growth period - by mid-July it has gone to seed and dried up. That makes it fuel for wildfire at a time when native plants still retain moisture. Cheatgrass-infested areas are prone to more frequent wildfires that end up killing the living native grasses.

    Many of the ecosystems that cheatgrass has invaded are seriously altered as native plants like perennial bunchgrass and sagebrush, which provide food and cover for wildlife, are pushed out.

    Source: U.S. Fish and Wildlife Service

The scourge of the West - cheatgrass - has become so ubiquitous that many have given up the fight to eradicate it. But not U.S. Department of Agriculture researcher Ann Kennedy.

The scientist went on a matchmaking mission in her laboratory to find the perfect mate for cheatgrass. Not an eHarmony-type mate, but more like a black widow-type mate. And Kennedy thinks she has found it in a naturally occurring soil bacteria that specifically targets cheatgrass, showing no interest in native grasses and plants.

The bacteria, called ACK55, is being tested on a 7-acre cheatgrass-infested plot at Deer Flat National Wildlife Refuge in Canyon County.

Cheatgrass is a problem for several reasons, said Deer Flat biologist Addison Mohler. In addition to being invasive and prolific - which forced out native grasses - it provides little food value to wildlife and cattle but high fuel value for wildfire.

Cheatgrass has a natural advantage over native grasses. It greens up early in the spring, while other grasses are dormant, giving it a head start at consuming precious moisture and nutrients. Then it dries out early, making it more susceptible to summer fires that also kill more beneficial plants. And even then it cheats - recovering quickly, thriving in areas disturbed by fires, roads or grazing.

It's even a visual blight, since it turns our Foothills browner earlier than the native grasses it displaces.

The bacteria attack it by colonizing emerging cheatgrass roots in the spring. Without healthy roots, it can't pull in water and nutrients.

Some herbicides are available that target cheatgrass. But the naturally occurring soil bacteria, called a biopesticide, could be a better solution.

"A biopesticide is much more cost-effective than an herbicide and less damaging to the environment and human health," said Hilda Diaz-Soltero, senior invasive species liaison for the U.S. Department of Agriculture.

A field trial at Hanford Reach National Monument/Saddle Mountain National Wildlife Refuge in south-central Washington dramatically reduced cheatgrass in three to five years, while not hurting other plants or animals, according to U.S. Fish and Wildlife Service officials.

Federal scientists selected Deer Flat for a larger-scale, multiyear field test because it has a large section of land with a "monoculture" of cheatgrass, Mohler said.

Scientists applied the cheatgrass-inhibiting bacteria in November and are monitoring it through soil tests, plant counts and photography.

"It will be a couple years before we can see the effect … and then the cheatgrass will really start to get hammered," Mohler said.

The USDA must approve ACK55 as a biopesticide, which could take several years before it can be licensed for commercial distribution.

"Everybody has just kind of given up on cheatgrass … it has won," Mohler said. "But this bacteria could be revolutionary."

Cynthia Sewell: 377-6428, Twitter: @CynthiaSewell

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