An Invasion Problem:

Leafy Spurge and its Management Efforts in Dinosaur National Monument and the Greater Yampa River Area

The Antagonist

Leafy spurge (Euphorbia esula) is native to the continents of Europe and Asia, but is currently causing mass amounts of destruction across farmlands and prairies in North America. The plant grows to be about three feet tall, and has distinctive yellow-green leaves that make it identifiable from far distances. On the inside leafy spurge contains a milky toxic latex sap that causes rashes on human skin, and can cause illness or death in cattle and horses if eaten (although sheep and goats are able to digest it).

It is especially difficult to control because it is a perennial plant, living many years, and resistant to most chemical herbicides and produces strong resilient root systems. Since not everything can eat it, and most herbicides are not effective, leafy spurge spreads rapidly over crop fields and pasture land, rendering it useless for agricultural production. Leafy spurge causes upwards of $120 million annually in agriculturally related economic losses in North and South Dakota, Montana, and Wyoming. In non-agriculture related economic losses, leafy spurge is expected to account for $10 million in watershed damages and recreation impacts in the same region.

Close up of a leafy spurge plant

Leafy spurge plant in seed.

Implications

When leafy spurge grows in pastures and cropland it impacts livestock health, reducing the amount of food that can be produced. This plant poses a risk to animal health through the toxic sap, and through decreasing the edible plants that grow in pastures. This poses a threat to human health through decreased food availability and decreased income from unusable fields. Also, as farmers are tempted to spray leafy spurge with lots of herbicides, the amount of chemicals added to farmland increases, which also may pose long term health risks for humans. Leafy spurge poses an environmental threat because it dominates landscapes and excludes native plant species. Wildlife, including many popular hunting species, then cannot eat their usual diets and may be more at risk for diseases.

River Travel

Currently, leafy spurge is threatening farms and pasture land in northern Colorado. The Yampa River, which runs east to west through the region, eventually converging with the Green River inside Dinosaur National Monument, meanders through this agricultural land. Seasonal flooding, heavy rain, and wind moves leafy spurge seeds into the river where they travel downstream. With the river as an effective mode of transportation, leafy spurge threatens to travel even farther west in to northeast Utah if not successfully managed.

Watch this video from the Yampa River Leafy Spurge Project to learn more about leafy spurge in the area and efforts to manage it.


Dinosaur National Monument

Drag the slider to see each full photo. Fossilized dinosaur bones in the Quarry Exhibit Hall (left) and the Green River and Steamboat Rock at Echo Park (right).

The Yampa River is what brings leafy spurge from farmlands into Dinosaur National Monument. The infographic below describes the process of spurge traveling from farmlands into the monument.

The process of leafy spurge arriving in Dinosaur National Monument and implications if management efforts are not successful.


Management Efforts

Leafy spurge on a river bank east of Dinosaur National Monument

Leafy spurge along a river bank east of Dinosaur National Monument

Spraying

For the most part, herbicides are not an effective treatment for leafy spurge in the Yampa River region. While some herbicides approved for farm and pasture land in some of the area, they cannot be used close to water, in areas with shallow water tables, or in areas prone to seasonal flooding.

This poses a limitation for Dinosaur National Monument as most of the patches grow on river banks. The Yampa River is the main sources of leafy spurge seeds that travel into the monument.

For more information on the specific chemicals used in leafy spurge management on crop and pasture land, click on the website link below from the Missouri Department of Conservation.

Pulling

One of the main management tactics in Dinosaur National Monument is hand pulling. This means taking teams of monument staff and volunteers down the Yampa River corridor using rafts and stopping at leafy spurge patches on river banks to pull out as many flowering plants as possible. These trips take several days, and are very hot and tiring. The leafy spurge gets packed into bags and loaded onto the rafts to be taken out of the monument and disposed of properly.

The rafts and the boat operators who row them are critical to the pulling effort because the distance would take too long to walk and the plants would get too heavy to carry out on foot.

Since the Yampa River is not dam-controlled, it does not always have enough water for rafts to access the Yampa Canyon. Typically by July, the river is too shallow for the large boats, so the pulling trips have to occur in the beginning of the season.

Staff and volunteers hand pulling leafy spurge, aided by a long-necked dinosaur.

Biological Controls

Biological controls are animals, birds, insects, or other living things that naturally prey on the species of focus. In the case of leafy spurge there are four known insects that eat the plant as part of their regular diets. They can be a very useful tool in invasive species management because they constantly attack the plants and once they are established in an area they require less monitoring. The insects do not kill all of the plants, so do not eradicate the leafy spurge, but they do make the patches smaller and less dense. This reduces the spread downstream and allows native vegetation to grow once again on the river banks.

In some invasive species cases, the introduction of biological controls is risky because they can cause damage to the habitat in unexpected ways. However, the four insects used in leafy spurge management were extensively studied for over twenty years and have not been shown to damage their new environments.

To collect the insects, Dinosaur National Monument staff and members of the Yampa River Leafy Spurge Project travel to other places in Colorado with established populations of the biological control species. Using gentle nets, they catch as many insects as possible and transport them back to northwest Colorado to be released along the Yampa River. The insects can also be sourced from farmlands farther north in Montana. After several months the staff will return to the release sites to search for the insects (using nets) to see if they have successfully made new homes in the leafy spurge patches.

This method has been proven to be successful in other areas, and researchers are beginning to see the leafy spurge patches shrink with the presence of the insects.

Scroll down the graphic below to learn about each of the control species.

The four main biological control insect species for leafy spurge along the Yampa River corridor. Top and bottom left: flea beetles (Apthona spp.); top right: leafy spurge hawk moth (Hyles euphorbiae); bottom right: leafy spurge stem boring beetle (Oberea erythrocephala). Image from Yampa River Leafy Spurge Project


Community

For management to be successful, leafy spurge must be controlled at the source and in the patches along the river where it is currently established. Dinosaur National Monument is partnered with the Yampa River Leafy Spurge Project, as well as several other stakeholders to tackle this issue both within the monument and in the farming communities upstream of the monument. Click the link below to learn more about the Yampa River Leafy Spurge Project efforts.

The other project partners in the effort to manage leafy spurge in the area are Moffat County, Routt County, Colorado First Conservation District, Colorado Parks and Wildlife, Colorado State Land Board, Concerned Citizens, CSU Routt County Extension, Community Agriculture Alliance, Friends of the Yampa, Little Snake Field Office BLM, Private Landowners, Natural Resource Conservation Service, The Nature Conservancy, and Yampa River System Legacy Partnership.

Moving Forward

Close up of a leafy spurge plant

Leafy Spurge Plant

The leafy spurge infestation of the Yampa River corridor, including the farmlands nearby and Dinosaur National Monument, poses a large threat to farmland productivity and wild ecosystems in the area. It also has the potential to spread farther south into Utah and along the Colorado River corridor as well.

To effectively manage this problem, it will take collaboration and dedication from all of the project partners, as well as broad community education and involvement.

There are several ways for anyone to become more informed and involved in leafy spurge management.

  1. Volunteer pulling leafy spurge
  2. Help monitor biological control insect populations
  3. Donate to the Yampa River Leafy Spurge Project to help fund education and outreach to public and private landowners in the Yampa Valley.

Visit the Yampa River Leafy Spurge Project website for contact, volunteer, and donation information (linked in the Community section above).

You cannot get through a single day without having an impact on the world around you. What you do makes a difference, and you have to decide what kind of difference you want to make. - Jane Goodall


Acknowledgements

This StoryMap was made possible by Emily Spencer and Dinosaur National Monument, Tamara Naumann and the Yampa River Leafy Spurge Project, and the Scientists in Parks Fellowship.


StoryMap Author: Mary Buford Turnage, M.S. |Scientists in Parks Fellow at Dinosaur National Monument 2021|

Leafy spurge plant in seed.

Drag the slider to see each full photo. Fossilized dinosaur bones in the Quarry Exhibit Hall (left) and the Green River and Steamboat Rock at Echo Park (right).

The process of leafy spurge arriving in Dinosaur National Monument and implications if management efforts are not successful.

Leafy spurge along a river bank east of Dinosaur National Monument

The four main biological control insect species for leafy spurge along the Yampa River corridor. Top and bottom left: flea beetles (Apthona spp.); top right: leafy spurge hawk moth (Hyles euphorbiae); bottom right: leafy spurge stem boring beetle (Oberea erythrocephala). Image from Yampa River Leafy Spurge Project

Leafy Spurge Plant