Protecting Watershed Values in Southeast Wyoming

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Russian olive trees are cut at ground level and stumps are treated with Garlon 4 Ultra with bark oil immediately following cutting.

The North Platte River flows through Colorado and Wyoming before joining with the South Platte River in western Nebraska near the city of North Platte. The river drains a large portion of southeastern Wyoming, providing critical services to the region ranging from irrigation to recreation.

The impact of noxious weeds and invasive trees, particularly Russian olive (Elaegnus angustifolia) and saltcedar (Tamarix spp.), on the ecosystem of the North Platte watershed became evident to long-time weed superintendent Steve Brill with Goshen County Weed and Pest District. “The North Platte River is critical to the economy and natural resource base in Goshen County,” explains Brill. “We started a saltcedar control program along the river in fall of 2006 and included Russian olive in our efforts by 2007. It didn’t take us long to realize that this was a huge task and we needed to coordinate with upstream counties and landowners in order to make the control program successful.”

The five counties encompassing the North Platte River in Wyoming joined forces in 2007 and formed the Upper North Platte River Weed Management Area (WMA) to control Russian olive and saltcedar along the river and its tributaries. Starting at the Colorado state line, the counties within the project area include Carbon, Natrona, Converse, Platte and Goshen [BOX 1]. The goal of the project is to protect and improve water resources, wildlife habitat, and native plants and animals by controlling invasive trees. A side benefit of the control effort is maintaining a more open river channel to minimize potential flooding along the river and its tributaries.

BOX 1.

“Although the North Platte watershed includes a diverse mix of ownership, the majority of land along the river is privately owned,” explains Dana Erdman, coordinator for the project. “We need these landowners to support our control effort, so public education and outreach on the impact of invasive trees to watershed values is a critical component of our plan.” Russian olive has been planted in windbreaks in Wyoming for many years, so the education program focuses on impacts caused when these invasive trees establish in riparian areas. Counties also focus on removal efforts along waterways, allowing Russian olive to remain in upland windbreaks or ornamental plantings.


One of the public education hallmarks of the project is a video highlighting the value of the North Platte River and impact of invasive plants on watershed values, agriculture and recreation. “The North Platte river is famous for fly fishing,” explains Brill. “So there was interest from fishing organizations and other recreational groups along with private, county, state and federal partners to expand the video.” [BOX 2]

MANAGEMENT EFFORTS on saltcedar within the five-county area started as early as 2004 but quickly expanded when Russian olive was added to the Wyoming noxious weed list in 2007. Control methods include saltcedar foliar, basal bark, and cut-stump herbicide applications, mechanical removal of larger Russian olive and saltcedar trees, and release of the biological control agent Diorhabda elongata on saltcedar.

Dedication, hard work and persistence typify the control effort. In Goshen County, two to three individuals using backpack sprayers did the bulk of saltcedar treatments along 86 miles of the North Platte and Laramie River. “It really gets us in shape for hunting season,” jokes Brill about the number of miles walked as part of the control effort. “We started at the Wyoming and Nebraska state line and progressed upstream treating both sides of the North Platte and Laramie River banks, islands and reservoirs in Goshen County.”

Steve Brill, Goshen County Weed & Pest, Torrington, WY

Since 2007, county weed districts and other partners in the Upper North Platte River WMA have treated about 4,400 acres of saltcedar and 2,800 acres of Russian olive. “The progress we’ve made to date is just great,” says Brill. “We are restoring open stands of native cottonwood and willows that have a productive grass understory. Several years ago these riparian areas were choked with saltcedar and Russian olive.”

Partners directly involved in the control effort include county weed and pest districts, conservation districts, private landowners, Bureau of Reclamation, Wyoming Game and Fish, Natural Resource Conservation Service, Northern Great Plants Exotic Plant Management Team and others. The scope of control and containment programs varies among counties based on the level of infestation and available resources.

Before (top) and after photos where Russian olive trees were removed. Maintaining a desirable grass understory reduces invasion of weedy plants, provides protects soil from erosion, improves wildlife habitat and provides livestock grazing.

The majority of control has been basal bark or cut stump herbicide treatments with a 25% solution of Garlon® 4 Ultra (1 quart Garlon 4 Ultra to 3 quarts bark oil). “We selected Garlon because grasses are very tolerant to the herbicide allowing us to maintain a desirable understory plant community. Overall, Garlon is providing good control especially with basal bark treatments on smaller trees, but we had some re-growth on large Russian olive,” explains Brill. “Based on our treatment techniques and label guidelines, we increased our rate to a 50% solution of Garlon 4 Ultra in bark oil in October 2011 for both basal bark and cut stump application and will monitor results of the treatments.” A 5% solution of Habitat* was also used as a cut stump treatment on limited sites. “We only use Habitat as a retreatment on a small percent of our cut stumps,”explains Brill. “You have to be very selective where you use Habitat since it kills all the other vegetation around the stump. You have to reseed the site or end up with bare ground which is susceptible to establishment by other invasive plants.”

The management plan also includes mechanical shearing (cutting) large Russian olive trees at ground level and applying Garlon® 4 Ultra with bark oil immediately following cutting. Goshen County is still trying to find the best use for the woody biomass once trees are cut. In some areas the wood is stacked to make natural windbreaks for cattle and provide wildlife habitat. Trees are also mulched and the material sold, given away or used by the county.

“Dealing with residual biomass from tree and brush management projects is a real challenge,” explains Scott Bockness, leader for the Missouri River Watershed Coalition Conservation Innovative Grant (CIG) Project, which includes the Upper North Platte River WMA. Bockness has been working with partners in the WMA to investigate potential uses for the biomass. “Current test results indicate that biomass generated from the Russian olive and saltcedar management projects could be used for local biomass energy conversion,” says Bockness. “ It would be great to incorporate these plant materials into local and regional bioenergy assessments for future alternative energy projects.”

Partners are working together to investigate potential uses for tree biomass removed from sites. Piles of cut trees are stacked to create windbreaks for livestock, whereas others are mulched (shown above).

The Upper North Platte River WMA is committed to a long-term program to control Russian olive and saltcedar on the river and its tributaries. The project has united conservation organizations, private landowners, county weed and pest districts, and a host of other private, county, state and federal partners. “Even though there are a lot of partners in this project, Steve Brill is the real champion of our efforts,” explains Erdman. “He has been a leader and promoter for this project, and his hard work, vision and dedication is improving and protecting the watershed value of the North Platte River.”

Published 2012; trademark updated June 2019.

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