The leafy spurge invasion: Group aims to combat spread of invasive plant species
Local volunteers work to control invasive plant species along the Yampa River
Spend any time near the Yampa River in Moffat County and you will see the leafy spurge that has started to dominate bank vegetation over the past several decades.
Leafy spurge is an invasive plant species that was probably introduced to the area from out-of-state road or hay equipment as early as the 1950s, according to Yampa Valley Leafy Spurge Project volunteer Ben Beall.
The Yampa Valley Leafy Spurge Project is a community-led initiative that has been heavily involved in trying to manage the leafy spurge infestation over the past six to seven years.
The Yampa Valley saw a huge spread of leafy spurge in 2011, when river banks flooded, uprooting established leafy spurge plants and carrying the roots and seeds downstream.
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Yampa Valley Leafy Spurge Project volunteers (from left) Ben Beall, Pete Williams, Tim Corrigan explain leafy history before a river tour to raise awareness with community members (right) Jennifer Halloway.
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Yampa Valley Leafy Spurge volunteer, Pete Williams, holding up the head of a leafy spurge plant to show the flowers and the milky sap inside the stem.
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Volunteers (left) Tim Corrigan and Pete Williams explain how leafy spurge is spread along the river bank.
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Project volunteer, Pete Williams, swings a net through a patch of leafy spurge to capture beetles to determine whether there is a presence in this area.
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Pete Williams, examining the contents of a net after taking a sample for beetles in the leafy spurge path.
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Close-up of the contents inside of the net after taking a sample for beetles in a leafy spurge path.
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Leafy spurge volunteers take a closer look at the contents of the net from a sampling of a field containing leafy spurge and beetles.
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Overlooking a field with flowering leafy spurge plants.
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A stretch of the Yampa River bank with patches of leafy spurge.
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Close up of flowering leafy spurge plants with volunteers taking samples in the background.
Amber Delay/Craig Press
Once you have identified the bright green flowering plant lining the banks of the river, it is nearly impossible to miss.
Leafy spurge project volunteer John Husband explained that since the plant is not native to Northwest Colorado, it has no natural predators to stop it from crowding out the other vegetation. Leafy spurge has a strong strategy for reproduction, so once it’s established, it is extremely difficult to remove.
Beall explained that simply picking the plant is not effective, and there is a milky sap inside of the stalk that makes it toxic for humans to touch. The plant is also toxic for animals to eat, including horses and cattle, as well as deer and elk.
Because leafy spurge crowds out other plant species, it can make it difficult for roaming animals to forage near certain areas of the river, and it can have an impact on grazing and hay fields near the river.
The goal of the leafy spurge project is to reduce seed flow and keep the plant from spreading.
“Pulling it is not an effective strategy,” Beall said. “But it’s used as a placeholder until we have a better solution.”
One of the most common ways to deal with invasive plant species in the agriculture world is through herbicides. However, herbicides are not the ideal solution for several reasons. Herbicides aren’t selective and often kill everything where they are applied. While herbicides can effectively kill off everything, they don’t prevent the invasive plants from returning.
Herbicides are also not appropriate for use near the river, as the chemicals can contaminate the water source.
“We’re looking for a holistic approach,” Beall said.
There are other, more natural methods that can be used to control the spread of the plant. Leafy Spurge is native to Europe and Asia, but it doesn’t take over on those continents like it does in Northwest Colorado because it has natural predators to keep its growth in check.
One of the leafy spurge’s natural predators is the leafy spurge beetle, which feeds on the plant, causing it to produce fewer flowers and seeds.
According to Beall, the project group did some research to find that leafy spurge beetles were released about 30 years ago in 1989. After the beetles were released, however, there was little to no monitoring that took place to determine the effect.
That’s where the Yampa Valley Leafy Spurge Project came in to better understand the impact of the beetles.
The group has worked with several local and regional partners — including the Bureau of Land Management, Colorado Parks and Wildlife, and private landowners — to do a closer examination on the effect of these bio-controls on the invasive plant.
By mapping out the area and monitoring along the river, the project group found that the leafy spurge beetles have persisted in low numbers. The group also discovered some areas where the leafy spurge was showing signs of distress, meaning the plants weren’t flowering and seeding as much.
Now that the group has helped prove bio-controls can be effective, it could help boost local efforts to control the plant.
The goal would be to get higher established levels of leafy spurge beetles. The beetles are host specific, or they have evolved so closely with this specific plant they won’t eat other plants.
It is thought that increasing the number of beetles would have little effect on other plants in the areas while reducing the amount of leafy spurge and making more room for native species to thrive.
Project volunteer Pete Williams explained that bio-controls are about limiting invasive species so they don’t have such an impact, rather than getting rid of them all together.
“We’re looking for a more evened out wave where the plant is stressed,” Williams said. “Leafy spurge has had a free ride, and we need them to be more behaved.”
The Yampa Valley Leafy Spurge Project volunteers host a river float at least once a year to raise awareness about leafy spurge and the work that’s being done toward this project. One of the ways that the community can help is by getting more volunteers involved.
Anyone who is passionate about the outdoors and keeping the Yampa River healthy is welcome to attend a meeting for the leafy spurge project. Project updates and meeting information can be found on the website at http://www.YampaRiverLeafySpurgeproject.com.
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