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Waging war on invasive weeds

Written by Teresa Milner

Lovell – Combine the efforts private landowners and government agencies like the Wyoming Game and Fish Department, add in funding from sources the Wyoming Wildlife and Natural Resource Trust Fund, then top it off with cattle, goats, beetles and some heavy-duty machinery and you’ve got a recipe for success for winning the war on invasive weeds in Big Horn County.

For more than eight years members of the Yellowtail Coordinated Resource Management (CRM) group have been working to eradicate thickets of Russian olive, salt cedar, whitetop, knapweed and other invasive weeds on the Yellowtail Wildlife Habitat Management Area (WHMA) and adjacent private lands east of Lovell.  

Though the Russian olive tree has been used in the past for shelterbelts and erosion control, its ability to survive even the harshest conditions eventually became a liability. The trees have spread across the state, forming monocultures that displace native trees, consume massive amounts of water and provide little habitat diversity for wildlife. Salt cedar poses similar problems.

“Russian olive does provide some wildlife habitat, as well as shade and cover for cows,” says Jerry Altermatt, habitat extension biologist for the Wyoming Game and Fish Department. “The problem is that it is always moving to dominate the site, outcompeting native woody plants like cottonwood, buffalo berry and willows.”

The Yellowtail CRM was formed out of concern over the ecological degradation caused by the invasive plants in the Big Horn and lower Shoshone River systems. Game and Fish, Bureau of Reclamation, BLM and the National Park Service, as well as neighboring private landowners, the Big Horn County Weed and Pest, Shoshone Conservation District and NRCS are all members of the group.

Altermatt says removing aggressive Russian olive and salt cedar helps restore native woody plants and releases understory plants like grasses and broadleaf plants that provide food for wildlife and domestic livestock. Wildlife like deer, waterfowl, turkey and pheasants will benefit as native vegetation begins to flourish.

Controlling these species requires a number of tools, personnel use a tracked excavator to grind larger Russian olive trees to mulch, crews return to the treatment site the next fall to spray an herbicide on the resprouting Russian olives and the bases of small Russian olive trees and salt cedar plants not cut by the mulching machine are also treated with herbicide.

The mechanical and chemical treatments are supplemented with biological efforts and managers have turned to the leaf beetle, native to Asia, to help control salt cedar. The beetle eats the leaves of salt cedar, defoliating the plant.

“The beetles were slow to get started, but after two years, it just exploded. You could look down in the river bottom and see what looked like hundreds of dead salt cedar,” says Altermatt.  

Despite those early signs of success, the beetle population crashed for unknown reasons and the salt cedar started coming back.

“It will take multiple defoliations to really kill salt cedar. But any time you can stress the plant, it’s helpful in the overall effort,” explains Altermatt. “There is no silver bullet in controlling these plants. Beetles are just another tool in the box we can use.”

Boer goats are grazed over the treatment area from April to September to target species with browsing. Early in the year cattle are grazed in small, quarter-mile-wide pastures strategically located throughout the Shoshone River bottom to reduce the risk of wildfire.

“Grazing removes the fine fuels prior to the threat of spring wild fire, and rejuvenates grass and forb communities. The idea is that if a fire would occur and spread to those areas, it would burn out because of the lack of fuel load,” says Altermatt.

While ground is being gained in the war on weeds, efforts must be ongoing to maintain success.

“Once we get all the big stands of trees removed, we’ll begin maintenance mode,” explains Altermatt. “Then we can use a backpack sprayer every other year to treat resprouts or seedlings and stay ahead of the plants. It’s cheaper and easier to treat early when the trees are still small.”

As part of the reclamation process, cottonwood and willow cuttings have been planted in areas previously treated to remove Russian olive and salt cedar. To date, more than 1,000 acres on the Yellowtail WHMA and adjoining private lands have been treated with some combination of mechanical, chemical and biological tool.  

Paying for this war on weeds has also taken cooperation. Funding has been provided through sources like the Wyoming Wildlife and Natural Resource Trust, the Wyoming Game and Fish Department Trust Fund, the National Wild Turkey Federation, the Governor’s Big Game License Coalition, National Fish and Wildlife Foundation and the Shoshone Conservation District. Private landowners and other government agencies like the BLM and Big Horn Weed and Pest provide in-kind support by purchasing herbicides and equipment and providing on-the-ground labor.

Other invasive weed control projects are being implemented in Big Horn County along Shell Creek, Sage Creek and the Greybull River.

Though Wyoming’s rivers and streams will probably never be completely free of Russian olive, salt cedar and other invasive weeds, members of the wildlife and agriculture community will continue to work together to return the diverse habitat that supports a healthy mix of wildlife, forage for grazing and accessible recreational opportunities along the river corridors.

Teresa Milner is a correspondent for the Wyoming Livestock Roundup. Send comments on this article to This email address is being protected from spambots. You need JavaScript enabled to view it..