The Yampa Valley Leafy Spurge Project has been combatting the leafy spurge invasion along the banks of the Yampa River this summer, and now they have some more help.

The group recently released an estimated 30,000 leafy spurge beetles in targeted areas across Moffat and Routt counties, as other methods to curb the invasive weed’s growth have been largely ineffective.

Leafy spurge is a lime green, flowering weed that is aggressively taking over riverbanks from the upper Yampa River in Routt County to the Little Yampa Canyon in Moffat County. 

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Volunteers, government entities and private landowners have joined forces in their efforts to control the invasive plant species, which not only degrades the riparian ecosystem, but is toxic to humans and animals, including most local wildlife and livestock. 

Leafy Spurge Project volunteer Ben Beall said during a river tour earlier this summer that the plant species was likely introduced to the Yampa Valley by out-of-state road or haying equipment as early as the 1950s.

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The intrusive presence of leafy spurge has the potential to affect local landowners who harvest hay on land neighboring the river, as well as crowd out native plant species along the river that are grazed by wildlife.

Once leafy spurge is established, the weed is extremely difficult to remove due to its effective reproductive strategy and because the milky sap inside the stem is toxic for humans to touch.

Herbicides, which are most commonly used to address invasive plants, are also ineffective against leafy spurge because they aren’t selective in the plants they kill and don’t prevent leafy spurge from returning. The herbicides also contain chemicals that could contaminate the water supply if released near the Yampa River. 

As a result, releasing one of the plant’s natural predators — the leafy spurge beetle — into the landscape is seen as the most effective way to address the leafy spurge infestation.

Because these beetles are designed specifically to eat leafy spurge, having a healthy presence of them will hopefully help keep the leafy spurge in balance with the surrounding environment. 

During the 2022 season, 30,000 leafy spurge beetles were released into infestations of the invasive weed by Leafy Spurge Project volunteers and Moffat and Routt County partners. The efforts this summer far exceeded the project’s goal of releasing 10,000 beetles into infested areas along the Yampa River. 

There are two species of leafy spurge beetles  — Aphthona and Oberea — both of which already have a small presence in some areas along the Yampa River, including where there have been experiments with smaller releases in areas densely populated with leafy spurge. 

One of the primary focuses of the Leafy Spurge Project is to continue to follow up with monitoring of the beetles and their effects on the infestation. Although there is evidence of previous beetle releases in their continued presence, prior to the Leafy Spurge Project, there wasn’t consistent monitoring of the beetles’ effects. 

One of the project leaders, Tamara Naumann, explained that bio control is not about eradicating the plant species altogether, so the leafy spurge beetles are not going to destroy the plant they live off of entirely. Rather, they will only damage the plants, which are their food source. 

Volunteers who monitored previous release sites were able to find good numbers of beetles still present in the area along with visual impacts on the leafy spurge plants.

Naumann said the experiments are considered successful if the leafy spurge growth is stunted, there are fewer flowering plants or tiny leaves on the spurge plants, and if they observe tall, dense clumps of plants spread out in the area. 

Through June, Leafy Spurge Project volunteers were busy collecting beetles at the Lowry State Land Board Property under the direction of Biological Control Specialist John Kaltenbach with the Colorado Department of Agriculture. 

Beall and Naumann were joined by volunteer Pete Williams and Terry Audesirk for the beetle collection, which was accomplished using sweep nets within large patches of leafy spurge on the property. Nearly half of the 30,000 beetles released were collected in this fashion, and others were purchased from suppliers in Montana. 

Kaltenbach and CDA staff assisted the Leafy Spurge Project volunteers as they sorted and packed 14,000 leafy spurge beetles that were collected. The beetles were placed in small flasks, each containing 1,000 beetles — about two teaspoons — to be later distributed to volunteers for release. 

After the beetles were sorted, project volunteers met with Moffat County Weed and Pest Management and Bureau of Land Management officials and gave them 2,000 beetles to release on BLM property in Tepee Draw. 

Naumann, Williams and Beall did a river float through the Little Yampa Canyon to release another 10,000 beetles across five sites on BLM land in the last 15 miles of the canyon before taking out at Duffy Mountain. These sites were mapped by the Leafy Spurge Project volunteers in 2019 as having moderate or dense leafy spurge infestations. 

Several thousand beetles were released at two sites in the Maybell area and two sites west of Loudy-Simpson Park south of Craig. 

The project also integrated education for local youth in a two-day release event at the end of June. Leafy Spurge Project volunteers along with CPW, BLM and Moffat County CSU Extension office released another 2,000 beetles on the Yampa River State Wildlife Area with the help of five youth from Yampatika and seven youth from the Boys and Girls Clubs of Craig and their adult mentors. 

Leafy Spurge Project volunteers later released 6,000 more beetles at the Yampa River State Wildlife Area. The hope is that this site could develop into a local leafy spurge beetle nursery, which could provide more beetles for release in future years. 

Volunteers plan on continuing to monitor the release sites to keep track of the beetle populations and their effect on the leafy spurge.

The Leafy Spurge Project can always use more volunteers to help with the ongoing effort. For more, go to YampaRiverLeafySpurgeProject.com.