Partnership protects greater sage-grouse habitat from invasive plants

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and others to keep invasive plants out of greater sage-grouse (Centrocercus urophasianus) habitat.

The South Hudson-Government Draw Leafy Spurge Mapping and Treatment Project encompasses nearly 215,000 acres in the heart of sage-grouse country east of Lander, Wyoming and south of the small community of Hudson. About 85 percent of the area consists of lands controlled by the BLM. 

Leafy spurge (Euphorbia esula) is a state-designated noxious weed infesting a significant amount of the project area, much of which is within the Greater South Pass sage-grouse core management area. According to the local sage-grouse conservation plan (, the sagebrush grasslands and open spaces of the area are “recognized as one of the highest density sage-grouse areas in the state of Wyoming, and represent one of the strongholds for breeding populations of sage-grouse in western North America.”

Preventing the introduction and proliferation of invasive plants is an important objective of the local working group’s sage-grouse conservation plan. The plan lists vegetation management, particularly invasive plants, as one of the factors impacting sage-grouse populations. If left untreated, non-native invasive plants such as leafy spurge can dominate a landscape and create a monoculture consisting of a single dominant species. Controlling leafy spurge and other newly invading non-native plants allows a greater diversity of native vegetation to flourish, which benefits greater sage-grouse and other wildlife. 

Kimberly Johnson, assistant supervisor for Fremont County Weed and Pest District, and Susan Oberlie, wildlife biologist for BLM Lander Field Office, kickstarted the ambitious project in the summer of 2014. “Managing leafy spurge in this area has been a priority for us because it encompasses a significant livestock grazing allotment as well as pristine sage-grouse habitat,” explains Johnson. 

The first step in the project included GPS-mapping of invasive plants. Approximately 58,000 acres were mapped in 2014, and an additional 150,000 acres are scheduled to be surveyed for leafy spurge and other noxious weeds in 2015 and 2016. 

“Gathering GPS data to create a noxious weed inventory is important for developing a treatment plan that will be effective and economically viable, especially for such a large area,” said Johnson, head of the Fremont County Weed and Pest’s GIS program. The survey includes not only leafy spurge but also newly invading species like Dalmatian toadflax (Linaria dalmatica) and Scotch thistle (Onopordum acanthium) that are part of the county’s early detection, response program.

Herbicide treatments were initiated on leafy spurge in June 2015 to stop spread and control invasive plant infestations. Tordon® 22K herbicide at 1 pint per acre plus Overdrive at 4 ounces per acre will be applied to leafy spurge on upland sites near roads and trails. 

“We plan to include ForeFront® HL [GrazonNext® HL] at 2 pints per acre (pt/A) plus Overdrive at 4 ounces product per acre and evaluate this mix versus the Weedmaster applications along ephemeral drainages and watering areas,” explains Aaron Foster, Fremont County Weed and Pest supervisor. “We are waiting for approval to apply ForeFront® HL and Milestone on BLM lands.” In addition to leafy spurge, rapid response crews mapped and treated newly invading noxious weeds such as Scotch thistle and Dalmatian toadflax, along with musk thistle (Carduus nutans) and saltcedar (Tamarix spp.).

“It’s a huge area and some of the leafy spurge infestations are quite severe,” said Foster. “To treat the entire infestation with herbicides would not be economical or sustainable, so we plan to use an integrated approach beginning with treatments in places where we surveyed in 2014.”

Small infestations will be targeted for eradication, while larger infestations will be contained by treating the outside edges of patches with herbicides. Biological control insects, including flea beetles (Aphthona sp.), have been released on large infestations in previous years and will continue to play a role in treatment efforts. 

Fremont County Weed and Pest also plans to develop outreach programs for livestock producers and recreational users in an effort to reduce the spread of noxious weeds by people and their livestock. The region is popular for recreational pursuits, such as off-highway vehicle use, horseback riding and target shooting, and also has several state and BLM grazing allotments.

After the three-year project is completed, Fremont County Weed and Pest and the BLM will continue to monitor for invasive plants and will consider additional invasive plant treatments as needed. The county currently shares control costs on private lands within the project area.

“Keeping our open spaces free of invasive plants requires a long term commitment from everyone involved,” Foster said. “We all have a stake in the future of Wyoming’s sage-grouse and in keeping our native wildlife habitat intact.” 

Published Sept 2015; trademark updated June 2019.

Box 1. Project Partners

Estimated cost for a three-year project is $150,000.

The WRSR Sage-Grouse Working Group provided a grant to the South Hudson-Government Draw Leafy Spurge Mapping and Treatment Project. Funding was from the Wyoming Sage-Grouse Conservation Fund via the Wyoming Game and Fish Commission, and Wyoming Game and Fish Department. The local working group is one of eight established throughout Wyoming for the purpose of conserving sage-grouse. Each working group is comprised of representatives of local interests such as agriculture, conservation and industry, and federal, state, local and tribal governments. 

Partners include

  • Freemont County Weed and Pest Control District

  • U.S. Bureau of Land Management (BLM)

  • Wind River/Sweetwater River (WRSR) Sage-Grouse Working Group

  • Wyoming Department of Transportation

  • Wyoming State Lands

  • PopoAgie Conservation District

  • Participating private landowners



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Milestone and ForeFront HL [GrazonNext HL] are not registered for sale or use in all states. Contact your state pesticide regulatory agency to determine if a product is registered for sale or use in your state. When treating areas in and around roadside or utility rights-of-way that are or will be grazed, hayed or planted to forage, important label precautions apply regarding harvesting hay from treated sites, using manure from animals grazing on treated areas or rotating the treated area to sensitive crops. See the product label for details. State restrictions on the sale and use of Milestone apply. Consult the label before purchase or use for full details.

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