Bear Lake • When those who study this Utah-Idaho lake first spotted invasive Eurasian watermilfoil in its crystalline waters, they thought they could wipe it out. Years of limited treatments later, those hopes have sunk.
The fast-growing weed is now entrenched, officials say, threatening water clarity, recreational safety and the lake’s unique ecosystem.
Jessie Danninger, a program manager with Utah’s Division of Forestry, Fire and State Lands, has spent the summer mapping the plant with new technology that measures vegetation through the water column, giving researchers their clearest picture yet of its reach.
“We found a lot more of it,” said Danninger, “than we thought was originally there.”
The invasive weed, which first appeared in the lake in 2019, spreads fast and forms thick, tangled masses.
It can ruin watercraft like Jet Skis, trap unsuspecting swimmers, and clog irrigation systems vital to farmers and ranchers. It also chokes out the lake’s native vegetation.
Despite ongoing efforts to treat the milfoil from both sides of the lake, Danninger said the plant’s growth could be worsening because current treatments may not be effective. She said factors like the lake’s water chemistry and temperature might be limiting how well herbicides work.
However, she said, the increase in reported milfoil might also be due to more thorough monitoring.
“Because our monitoring is a little bit more robust, we are finding more milfoil,” she said. “That doesn’t mean that it hasn’t always been there. Once you start looking for more, you start finding more.”
Either way, Utah officials say eliminating the milfoil entirely is extremely unlikely. It’s now a question of containing it.
Brady Long, director of Bear Lake Watch, an environmental nonprofit dedicated to research and advocacy for the lake, attributes the milfoil’s spread to a lack of coordination between Utah and Idaho.
“It’s one of the most treasured assets in all of the state,” Long said, “but unfortunately, Idaho just doesn’t seem to recognize it at the same level.”
On the Utah side, new efforts are underway to tackle the problem, including plans to install a dip tank at the new boat marina where watercraft entering the lake can be quickly checked and decontaminated for invasive species.
Current decontamination methods — like those at a station near Garden City — can take anywhere from 30 minutes to two hours, depending on wait times and cleaning steps.
Idaho, however, says it has no similar plans or additional funding in place. Long, meanwhile, said trying to limit the plant’s spread on only one side of the lake is nearly pointless.
The Gem State typically treats milfoil late in the summer when the plant is at its peak growth and most vulnerable. But last year, Idaho treated only 22 acres out of more than 150 acres surveyed on its side of the lake, focusing solely on high-risk areas near boat ramps and marinas.
Long contends Idaho’s approach last year contributed to the irreversible spread of the plant.
“I have to admit, I’m pretty heartbroken about the whole situation,” he said. “It’s as if everything that Utah does is undermined by the actions of Idaho.”
For the Gem State’s part, Sydney Kennedy, spokesperson for the Idaho Department of Agriculture, said the department has been actively collaborating with Utah agencies and Bear Lake Watch by sharing survey data and treatment plans.
So far this year, Kennedy said, Idaho staff have conducted over 1,500 surveys along the North Beach and northeastern shoreline.
Currently, the department has not determined any treatment areas or selected any products to stave off the plant, but treatments are still planned for later this year.
“Since the beginning,” Kennedy said, “ISDA has been committed to collaboration with all agencies and community groups involved in Bear Lake, recognizing its unique nature as a dynamic waterbody shared between two states.”
The department has prioritized treating high-risk areas where boats enter and exit the water, she said, since Eurasian watermilfoil spreads through fragmentation.
The typical response strategy for aquatic noxious weeds aims first for eradication, she said. However, in Bear Lake’s case, the department is now in an active management phase, working to control its spread.
The department also has to work within a tight statewide budget, she added, covering many water bodies.
“It really is,” Kennedy said, “just a big balancing act and puzzle across the state.”
