Lake treatment results look positive

Destructive plants clogging the waters of Shawano Lake are in retreat after large-scale herbicide treatments designed to clear the lake for better boating, fishing and swimming.

Early test results show that chemical applications carried out this summer have reduced by more than 90 percent the lake’s main targeted invasive plant species.

Officials caution that more testing is needed, but they are encouraged by preliminary indications that the herbicide worked even better than anticipated in improving water quality.

“All signs point to a successful treatment,” said Eddie Heath, an ecologist on the project with the consulting firm Onterra LLC.

Water samples collected from the 6,000-acre lake before and after the chemical treatments, Heath said, show that infestation of the invasive plant species known as Eurasian Water Milfoil has been reduced from affecting 17 percent of the lake to slightly more than 1 percent.

Test results also show minimal damage caused by the herbicide to native plant species that lake advocates hope will flourish once the invasive plants are out of the way.

Ray Zuelke, a board member of the group called Shawano Area Waterways Management, said the water is visibly cleaner since the chemical applications, and he believes the lake’s ecological system is healthier than ever.

“It’s incredible,” he said. “I never dreamed we could make it this good.”

Zuelke’s group of lakefront property owners and other lake boosters spearheaded the herbicide program after seeing the Eurasian Water Milfoil and other destructive plants grow so thick and large in Shawano Lake that they could snag motorboats and impede fish populations.

With a permit from the state Department of Natural Resources, the group combined $200,000 in state funds with $235,000 in private donations to conduct the treatments.

Crews from California-based firm Clean Waters Inc. were on the lake May 23 and May 24 to apply a herbicide known as DMA 4, using long hoses to send the chemical deep underwater where the targeted plants had taken root. The goal was to complete a large-scale application covering virtually the entire lake, but to do so without harming native plants or wildlife species.

Brenda Nordin, a lake biologist with the Department of Natural Resources, said she credited careful planning by all involved partners with executing the program and achieving the desired results. Nordin said the preliminary reports of 90 percent success or better was very impressive.

“That’s exactly what we like to hear,” she said.

Under state grant standards, a success rate of 75 percent is generally sufficient to judge a state-funded environmental program to be worthwhile.

In addition to the waterways management group, Zuelke said the lake cleanup effort has been supported, financially or otherwise, by local municipalities around the lake, county staff, area businesses and lakefront homeowners. The resulting improvement in water quality, he said, has impressed lake visitors and boosted prospects for increased tourism and economic activity.

“Everything’s very positive,” he said.

Heath said the small areas of Eurasian Water Milfoil that still exist — covering barely 1 percent of the lake — are somewhat concentrated on the lake’s western edge near Shawano Municipal Airport.

Consultants at De Pere-based Onterra will issue a formal report on the preliminary results within a few months. Then they plan to return to Shawano Lake next spring or summer to collect new water samples and look for signs of Eurasian Water Milfoil attempting a comeback.

Heath said nobody is certain yet whether the invasive plant has been eradicated or merely knocked down.

“If it comes back next year with a vengeance,” he said, “we’ll know the answer.”