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Northeast Wyoming Invasive Grass Working Group (NEWIGWG)

Mission: Minimize impacts to rangelands for wildlife and agriculture by reducing, containing, or eradicating medusahead and ventenata in northeast Wyoming.

The Issue

In June 2016, self-sustaining populations of two invasive grasses, medusahead (Taeniatherum caput-medusae) and ventenata (Ventenata dubia), were documented in northern Wyoming. Both species negatively impact rangeland resources for livestock and wildlife, with particularly strong impacts on sagebrush grassland communities. For example, Wyoming has the most sagebrush of any state at 43 million acres and is a stronghold for Greater Sage-grouse. These invasive grasses and their potential for spread pose a significant threat to fire return intervals, biodiversity, forage quality/quantity, climate resiliency, soil health, wildlife habitat, and other ecosystem goods and services. Both species have similar ecological impacts to cheatgrass, but with far worse forage value. 

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The above picture shows a small rangeland drainage infested with ventenata (the light blond patches) which is choking out the desirable forages

These annual grasses are known as winter annuals, which means they germinate from seed in the fall, overwinter and then continue growth early in the spring, effectively out-competing native rangeland species for water and nutrients.

Ventenata

Medusahead

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The above image shows the seed heads of medusahead as is matures. It also shows the two different lengths of awn-like glumes.

The above image shows the open panicle of a mature ventenata plant.

The above image shows the twisted base of a ventenata seed, and the longer curved awn of a medusahead seed.

The above image shows a once healthy rangeland now infested with medusahead.

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Ventenata can grow between 6-27 inches tall. It is bright green in early spring and turns a shiny blond color in the early summer. It has dark nodes as a seedling and throughout maturity. It has no visible hairs on the stem. The inflorescence is an open panicle at maturity. The seeds have awns that are twisted at the base and bend at a broad angle. When wet, the seeds will twist to promote burial into the soil (go to the Invasive Annual Grasses program page to see video).

Medusahead is bright green in the spring and it turns brown in early summer. It can grow to 6-24 inches tall and has slightly hairy, rolled leaf blades. Medusahead seeds have long rough feeling awns. The seeds fall out in late summer, but awn-like glumes of two lengths (shorter at the base and longer at the top) persist through the winter.

The above image shows the dark node on the stem of a ventenata plant.

About the Organization

Shortly after identification of ventenata and medusahead in Sheridan, multiple agencies collaborated to form the Northeast Wyoming Invasive Grasses Working Group (NEWIGWG), under the auspices of the Wyoming Cheatgrass Task Force (formed by MOU in 2005). The group has strategically managed invasive annual grasses for the past eight years and continues to fight towards eradicating and containing ventenata and medusahead in Wyoming.

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​NEWIGWG utilizes an EDRR (early detection rapid response) framework and containment zone strategy to improve rangeland health and sagebrush grassland habitat in Northeast Wyoming, and more importantly to prevent invasion into high quality sagebrush core habitat throughout the rest of Wyoming and the Great Plains ecoregion.

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Over the past six years we have surveyed and treated 170,000 acres, and retreated over 40,000 acres. We have also intensively monitored to assess treatment efficacy, non-target impacts, and inform adaptive management. Our partners have worked diligently to identify populations and treat landscape-scale infestations or assist private landowners in obtaining funding. 

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Here's a map showing NEWIGWG's current containment zone strategy for ventenata (light blue) and medusahead (dark blue).

Collaborative Research

NEWIGWG works closely with University of Wyoming IMAGINE (Institute for
Managing Annual Grasses Invading Natural Ecosystem). The collaboration works to
bridge the gap between research and on-the-ground practices to manage invasive
annual grasses. This partnership also provides opportunities for hands-on-experience
for students interested in rangeland weed science and landscape scale annual grass
management.

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For more information on IMAGINE visit their website at www.invasivegrasses.com

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The above image shows the UW intern team from 2022 responsible for the majority of invasive grass mapping that season.

Partners

  • Multiple private landowners

  • Weed and Pest Districts

    • Sheridan

    • Campbell

    • Johnson

    • Crook

    • Big Horn

    • Converse

  • U.S. Fish and Wildlife Service

  • Bureau of Land Management

  • U.S. Forest Service

  • Pheasants Forever

  • Natural Resources Conservation Service​

  • ENVU

  • Conservation Districts

    • Sheridan

    • Campbell County

    • Clear Creek

    • Powder River

  • University of Wyoming

  • Sheridan College

  • The Nature Conservancy

  • Wyoming Office of State Lands and Investments

  • Wyoming Game and Fish Department

  • American Bird Conservancy

  • Sheridan Community Land Trust

  • Wyoming Military Department

  • Corteva Agriscience

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