The Yampa River and its associated agricultural water delivery systems are spreading leafy spurge seeds downstream from large areas of infestation that have occupied floodplain areas between Hayden and Craig for several decades. The presence of leafy spurge in these difficult-to-treat riparian environments presents an especially difficult challenge to land managers.
The YRLSP seeks to address this problem through scientific research complementing local knowledge, aimed at the development of effective and sustainable leafy spurge management practices. To this end, the YRLSP has developed a relationship with Dr. Dan Tekiela, invasive weed scientist with the Department of Plant Science at the University of Wyoming, who has recruited two graduate students to work on leafy spurge research projects in the Yampa River Basin.
University of Wyoming graduate student Chloe Mattilio, under the direction of Dr. Tekiela, is developing remote-sensing mapping technology for detecting leafy spurge infestations across the entire Yampa River Basin, using high spatial resolution, multispectral satellite imagery. Chloe's development of the remote-sensing application includes correlation with the field mapping data being collected by YRLSP.
The leafy spurge invasion in the Yampa River Basin is still in progress—what we see today does not define the potential extent of future infestations. Under the direction of Dr. Tekiela, Chloe Mattilio is also working on an invasion risk predictive model for the basin that will aid leafy spurge control efforts now and into the future.
A primary resource is the extensive spatial dataset that has been developed in nearby Fremont County, Wyoming. Locations of leafy spurge populations have been recorded by Fremont County Weed & Pest for years, resulting in a robust dataset cataloging over 14,000 individual populations. By correlating environmental data for the Fremont County and Yampa River study area infestations (including soil type, texture, and pH; annual and monthly mean climate temperature and precipitation; location slope, elevation, and aspect; as well as infestation proximity to roads and developed areas), Chloe will build a predictive model that can be applied to the Yampa River Basin to identify and map locations where new leafy spurge infestations are more likely to occur in the future.
Integrated Pest Management
Leafy spurge is an extremely difficult species to effectively manage and many standard herbicide management options produce less than satisfactory results. In riparian areas, the problem is more complicated because several of the herbicides used to control leafy spurge in upland areas are not labelled for use near water. Because eradication is nearly impossible for well-established invasions, reducing seed production and the resulting spread of seed to new areas is the most responsible use of management resources to protect the Yampa River corridor, irrigated agricultural lands, and associated uplands.
Starting in 2019, University of Wyoming graduate student Hannah Kuhns, under the direction of Dr. Tekiela, began working on a project to quantify the current seed load produced by leafy spurge populations on the Yampa River, as well as establish best management practices for reducing cover and seed production of leafy spurge in diverse riparian systems. Currently, Hannah’s research is focusing on grazing by sheep, the use of a variety of herbicide applications safe to the water line, and combinations of both grazing and herbicide applications in the same growing season.