The ongoing battle against aquatic weeds on Kenosha County’s inland lakes is getting tougher as one of the most invasive species is developing an herbicide-resistant strain, and ongoing drought changes the landscape of the lakes.
Managing weed growth on lakes is the primary focus of the associations that work to care for inland lakes like Camp Lake and Paddock Lake. Without artificial controls, the lake weeds — especially invasive species like Eurasian watermilfoil — spread in thick mats, making it difficult for boats to move through the water.
The Eurasian species first showed up in the United States in about 1940. It is unclear how it first arrived, but it has spread to nearly every state. Beth Goeppinger, naturalist at Bong State Recreation Area, said the invasive species often spreads when fragments of the weed are brought in on boats.
“But birds bring it in too, herons carry it in on their feet,” Goeppinger said.
At Bong, Vern Wolf Lake has become so choked with milfoil it can be difficult to even paddle a kayak through the thick weeds.
Goeppinger said in 2000 the state actually drained the lake to try to eradicate milfoil. That worked for a time, she said, but in the last few years it came back with a vengeance. “We know its a problem,” she said. “We are working on a plan. But finding funding is a challenge," she said.
A troublesome invader
The weed causes trouble because it out-competes native species, and spreads in such thick mats it damages habitat for native fish and animals, as well as making life difficult for recreational boaters and fishermen.
For many local districts, last summer proved a particular challenge, as milfoil thrived and the usual treatments made a smaller dent in the growth.
“Not all the lakes experienced a huge milfoil bloom, but the ones that did really got it,” said Craig Helker, an aquatic plant management specialist with the Wisconsin Department of Natural Resources.
“It could have been related to lake levels — maybe the plants were there, but the water evaporated and exposed it,” Helker said. “Or maybe the warm temperatures made it really take off.”
Those big blooms of weeds — coupled with a drought that saw drops in lake levels that, in some areas, exposed several feet of mud along shorelines — left lake districts trying to keep up.
Using mechanical harvesters
Some lakes use mechanical harvesters to cut weeds and haul them away. In Paddock Lake, Administrator Tim Popanda said a two-man crew works on a mechanical weed harvester five days a week throughout the summer to try to keep weeds in check.
Popanda said when they began the annual harvest in May, the situation was already a bit out of control. “There wasn’t any snow cover on the lake last year, and the ice went out early. We really had spring arrive in March,” Popanda said. “So by the time we started harvesting, the weeds were just unbelieveable.”
He said the village hauled 280 truckloads — an estimated 2.2 million pounds of weeds — away to be composted.
Harvesters also were hamstrung by low lake levels, which allowed weeds to thrive in areas no longer accessible by mechanical harvesters.
“We tried to harvest a little later in the fall,” said Dennis Faber, a Salem supervisor and representative on the Camp and Center Lake Rehabilitation District. “But the lake was so low we were restricted on where we could go.”
Herbicides also used
Along with mechanical harvesting, many associations use herbicides to treat invasive weeds. In recent years, that too has become more challenging as Eurasian milfoil has adapted, hybridizing with native species and becoming resistant to chemical treatment.
Helker said a chemical called 2,4-D, or dichlorophenoxyacetic acid, is typically used to treat Eurasian milfoil. The chemical targets broadleaf weeds, but it does not affect native aquatic plant species. By hybridizing with natives, the hybrid is more difficult to kill.
The hybrid milfoil still will respond to chemical treatment, he said, but the chemical needs to be used at higher concentrations.
To know if a milfoil bloom is the hybrid, Helker said the plant needs genetic testing. “There’s no way to visually tell the difference.”
“It’s interesting. It is certainly something that makes control more costly, because you have to use a higher concentration and so you have to use more herbicides,” Helker said. “It makes it more expensive for the lake districts.”
Combination raises concerns
The combination of low water levels and higher weed concentrations had some residents worried about winter fish kills.
“I estimated that the water level was down 3.5 feet on Camp Lake,” Faber said. “The lake has an average depth of 5 feet, and 60 percent of it is 3 feet or less. That means now some of it is down to nothing.”
If there was heavy snow cover on the lakes, Faber worried, it could lead the unusually large weed beds to die off from lack of light, depleting oxygen levels in the water and causing fish kills.
With the winter shaping up to be unusually mild, with little snow, fish kills no longer seem to be likely, said Doug Welch, a fisheries biologist with the DNR. “The low water levels by themselves, I don’t think it’s going to be a hugely significant factor,” he said. “The driving factor will be the snow cover.”
For now, it seems like this winter will continue last year’s trend of little snow and little ice. If it is a repeat of last year, Popanda said, “the weeds are going to be even worse.”
He said he hopes to be prepared. “Next season we are going to get started a little earlier with our weed harvesting, and we’re going to be very aggressive with it.”
By Deneen Smith, www.KenoshaNews.com