Leafy spurge is a Eurasian weed that has been aggressively invading irrigated agricultural land and riparian habitats in western Routt and eastern Moffat counties for several decades. Its yellow-green flowers are most prominent along the river in May and June. Leafy spurge is poisonous to cattle and horses, degrades habitat for elk and other wildlife species, and pushes out native vegetation.

In the Yampa Valley, it continues to spread downstream — its seeds carried by the river — establishing new infestations along river banks and irrigation ditches.

In 2015, a group of concerned citizens, along with partner agencies and organizations, began working together to help land owners effectively manage this aggressive weed. The Yampa River Leafy Spurge Project is “just an informal group of folks who want to find solutions to a problem that threatens the place we live in, care about and make a living from,” said Ben Beall, local resident and former Routt County Commissioner.

The YRLSP’s goal is to provide a base of local information for developing effective and economical management strategies to curb the growth of leafy spurge along the Yampa River and its tributaries.

In 2019, the Yampa-White-Green Basin Roundtable and Moffat and Routt counties began cooperating to help fund the YRLSP’s mapping, scientific research and public outreach efforts. Friends of the Yampa stepped in to serve as the YRLSP’s local nonprofit fiscal agent to facilitate the work among partners.

This fall the University of Wyoming will be wrapping up several YRLSP-sponsored studies aimed at developing: technology using remote sensing to detect leafy spurge in large and inaccessible landscape areas; predictive models to help us understand how much vulnerable terrain we have in the Yampa Valley; and field-tested management tools appropriate for floodplain agricultural systems. These tools will help in planning future management efforts. Weed programs in Routt and Moffat counties are already using new information in their local management efforts.

Volunteers with the Yampa River Leafy Spurge Project have contributed hundreds of hours mapping spurge on the ground since 2019. The resulting maps are available on the YRLSP website. Data collected was also instrumental in the development and calibration of the remote sensing models developed by the University of Wyoming.

One of the most interesting contributions to leafy spurge management has been in the area of biological control.

“Our research suggests that the first releases of biocontrol insects in the Yampa Valley occurred three decades ago,” said Peter Williams, a YRLSP volunteer who heads up mapping, data management and website development for the group.

Many people thought the several beetle species released along the Yampa River in the ensuing years had failed to establish themselves. However, work conducted by YRLSP volunteers, in cooperation with the Colorado Department of Agriculture, has demonstrated that the beetles are still present from Hayden to Dinosaur National Monument.

In collaboration with the Colorado Department of Agriculture, the YRLSP has begun working on beefing up the biocontrol insect populations. In the past two years, approximately 30,000 additional insects have been released in carefully chosen locations here in the Yampa Valley.

Tamara Naumann is Yampa River Leafy Spurge Project volunteer and Friends of the Yampa board member.