Last fall starry stonewart was discovered in Wisconsin's Little Muskego Lake. The algae (which comes from an order of pondweeds) has since been discovered in Big Muskego Lake and a large portion of Bass Bay. Though it was only discovered recently, the algae's presence in Big Muskego Lake suggests it has been present for years.
Usually spread by boats, stonewart is a dense grower able to block out the light from native plants and take over native fish habitat. Local control efforts involve mechanical removal by scuba divers using their hands or underwater vacuums.
Further control options are being discussed. The full article is available here or through the link below.