A new treatment that was intended to kill zebra mussels in two Minnesota lakes was not successful, the Associated Press reports.
The Minnesota Department of Natural Resources used copper sulfate, a chemical used to treat swimmer's itch, to get rid of the invasive species in Lake Irene in Douglas County and Rose Lake in Otter Tail County. After the latest search of the lake this fall, scuba divers still found zebra mussels in both lakes.
The agency was hopeful the treatment was working after a search this summer did not show any sign of the invasive species.
Another experimental treatment called Zequanox is being tested on zebra mussels from Lake Carlos, about five miles north of Alexandria.
More than 50 Minnesota lakes are infested with zebra mussels.