Photo by Deb Gau While mats of curly leaf pondweed on Lake Yankton are no longer as visible as they were earlier this spring, members of the Balaton Sportsman's Club are still concerned what the invasive water plant means for the lake in the future.

BALATON — Lake Yankton is one of Balaton’s main features – but this spring, mats of curly leaf pondweed made it difficult to boat or fish on parts of the lake, Jeremy Swenson said.

“We did notice it last year, and this year it’s gotten progressively worse,” said Swenson, the president of the Balaton Sportsman’s Club. He estimated around 80 acres of the lake had CLP.

The invasive pondweed mats are no longer as visible as they were in May, but Balaton community members are still concerned for the future. Swenson said the Balaton Sportsman’s Club is looking into possible strategies for mitigating CLP. It’s a task that will likely take support from community organizations and residents, he said.

Swenson spoke to the Balaton City Council in May, and discussed possible options for addressing the pondweed problem on Lake Yankton. A DNR visual survey of the lake taken this spring found areas with dense patches of curly leaf pondweed, as well as areas of dense matting on the surface of the southern end of the lake, near Balaton’s boat launch and swimming beach.

Curly leaf pondweed is a water plant that is not native to North America, and competes with native water plants, said Jeffrey Flory, an aquatic invasive species specialist with the Minnesota DNR.

“It’s been around since the 1800s, so it is very widespread,” Flory said. CLP was most likely introduced around the same time that common carp were also introduced in Minnesota, he said.

CLP is not among the aquatic invasive species included on the Minnesota DNR’s listing of infested waters, Flory said. However, there are some resources, like the web-based mapping system EDDMapS (Early Detection and Distribution Mapping System), that have collected some reports of CLP in Minnesota.

On EDDMapS, the collected reports of CLP in southwest Minnesota include reports on Lake Yankton in May and June of this year. Photo identification showed mats of pondweed visible in the water at Lake Yankton, and near a dock.

Flory said that while CLP can provide shelter for fish or fish fry in some lakes, it also has a negative effect on populations of native water plants. CLP can tolerate low light levels, and even germinate under ice.

“It has a leg up on our native plants,” and competes with them, he said.

Swenson said the Balaton Sportsman’s Club has additional concerns about CLP. Besides forming big mats that make boating or fishing difficult, he said there was also a concern that the weeds will release nutrients into Lake Yankton after they die off, and cause algae blooms. It could undo efforts to help restore fish in the lake after a “significant” winterkill in 2018, he said.

According to EDDMapS data, CLP has been present in southwest Minnesota lakes since at least the 1990s. There were reported sightings at Brawner Lake in Camden State Park and at Lake Laura near Walnut Grove in 1991. CLP was also reported in Lake Benton in the 1990s, and over the years the Lake Benton community has worked to mitigate the invasive weed.

Swenson said the Balaton Sportsman’s Club reached out to the lake association in Lake Benton.

“They helped us with an action plan,” he said.

The options for managing curly leaf pondweed include removing the weeds with machinery, or using herbicide, Swenson said.

“I think treating it with chemicals would be the route we’re going to go,” he said.

However, it would be a long process.

Managing curly leaf pondweed on the lake would require a permit from the DNR. The chemical treatment could also only be applied to about 60 acres of the lake in one year. Lake Yankton is about 400 acres in size, Swenson said.

Swenson said it would take multiple years to try and control areas CLP using chemical treatments. For now, he said the Balaton Sportsman’s Club has taken the lead in trying to find a solution, as well as possible funds to help mitigate CLP on the lake.

“We’ve reached out to local organizations, and people who own property on the lake,” he said.