WILLIAMS BAY — The invasive plant known as starry stonewort has been found in two new locations on Geneva Lake, signaling that the destructive plant may be spreading.
The Geneva Lake Environmental Agency has called an emergency meeting of its board Aug. 8 to deal with the new threat.
Starry stonewort, which was previously thought to be isolated in one lagoon on the lake, is an invader that grows into thick bushes that can disrupt boating, fishing and other activities on a lake.
Onterra LLC De Pere, a lake management company, reported finding starry stonewort about two weeks ago during underwater plant surveys on Geneva Lake.
Ted Peters, director of the Geneva Lake Environmental Agency, said the two new locations are both on the south side of the lake. One is just outside of Trinke Lagoon in 10 feet of water, and the other is about a half mile east of the lagoon in 14 feet of water.
Trinke Lagoon, located in the town of Linn, is where the invasive plant first was discovered last fall.
The plant, which is actually a species of algae, is very difficult to control and almost impossible to eradicate. The plant extends far enough into sediment that poisons cannot kill the entire plant.
Kyle Mosel, an aquatic invasive species response coordinator with the state Department of Natural Resouces, said the next step will be to get a closer look at the Geneva Lake bottom to see the size of the new starry stonewort plants.
A diver or an underwater camera carried by a remote-controlled submersible might be sent down to survey the locations.
The state DNR has been working with the local environmental agency to combat the starry stonewort, which has never been found previously anywhere in Walworth County.
An emergency meeting of the environmental agency’s board of directors is scheduled for 6:30 p.m. Aug. 8 at George Williams College in Williams Bay to discuss the apparent spread of starry stonewort.
The agency is funded by the city of Lake Geneva, the villages of Fontana and Williams Bay and the town of Linn, all of which cover substantial parts of the Geneva Lake shoreline.
With the plant initially reported in Trinke Lagoon only, officials planned to dredge the lagoon bottom in hopes of removing all infestation. But that plan was postponed when dredging costs exceeded expectations at about $800,000.
Instead, officials tried applying chemicals to the bottom of the lagoon as a temporary measure while hoping to seek lower dredging costs later in the year.
Officials did not take steps to close the lagoon, despite fears that the starry stonewort could be spread to other areas of Geneva Lake by boat traffic in and out of the lagoon.
The new discovery of starry stonewort growth may change plans the state and local plan to dredge the infested portion of Trinke Lagoon.
Lake Geneva Alderman Doug Skates, who serves on the environmental agency board, said he was disappointed, but not surprised, that more starry stonewort plants have been found.
Skates said new methods of combating the invasive plant could include scouring the sites with a vacuum directed by a diver or covering the infested sites with smothering blankets called “benthic barriers.”
“I’m not sure that dredging is going to be effective, now that it’s in the lake,” he said.
The new plant surveys were conducted by running rakes along the lake bottom. Peters said the concentration of starry stonewort on the rakes was low, which he said could mean the plants are just starting to get established in those areas.
Starry stonewort is known to grow into thick mats if left unchecked.
The plant was first reported in Trinke Lagoon in October 2018. Officials speculate that it was accidentally transported by a boat that had not been properly cleaned.
The lagoon is a popular fishing spot, drawing in anglers from around the lake.