Watershed surveying curly-leaf pondweed growth on lake, to work on control measures

Published 12:53 pm Wednesday, June 12, 2024

Getting your Trinity Audio player ready...

An invasive species known as curly-leaf pondweed is flourishing on portions of Fountain Lake, and Shell Rock River Watershed District officials say it’s likely because of the lack of ice and snow cover on the lake earlier this year. 

Andy Henschel, administrator of the Watershed District, said curly-leaf grows early in the season and with the lack of ice and snow cover on the lake, the sun was able to penetrate down further into the lake, leading to its growth.

According to the Minnesota Department of Natural Resources, curly-leaf pondweed is generally the first pondweed to come up in the spring and dies back in mid-summer. 

Email newsletter signup

It is native to Eurasia, Africa and Australia but was likely introduced when common carp were intentionally introduced into Midwest waters as a game fish in the 1880, according to the DNR. The species was likely spread through the movement of watercraft and water-related equipment and was first noted in Minnesota around 1910. 

It generally grows from the shore to water depths of 15 feet and can grow up to 15 feet tall. It has lasagna-shaped leaves that can form dense mats at the water’s surface, according to the University of Minnesota Extension. 

Henschel said the Watershed District is trying to study the areas where the pondweed is located to figure out next steps to take to control it. 

It is conducting an orthophoto drone flyover to map out the areas on the lake where the curly-leaf pondweed is, and it is also conducting a vegetation survey. The hope is that by doing this they can keep track of where the vegetation is and whether it expands. Another purpose of the survey is to figure out what other native aquatic vegetation is in the lake. 

“Right now, where we’re seeing (curly-leaf) is everywhere we didn’t dredge,” he said.

Henschel said while the pondweed does have some benefits — it can be good for fish habitat — there are many negatives as well. It is not good for recreation, particularly people fishing from the shore, or for boat motors. 

He said there are two main ways to control curly-leaf pondweed and that is through an herbicide or a mechanical control, which would include cutting or pulling the plant by hand or with equipment. 

Both methods require a permit from the DNR. One drawback to an herbicide would be its effect on other native plants. 

Henschel said he hoped to have further discussions with the city about the issue likely in the fall, as the plant will begin dying off for the year in late June or early July.  

“We understand some of the headaches that dock owners have and some of the headaches fishermen have,” he said.