The latest confirmed detection of zebra mussels in Minnesota is being reported in a lake south of Detroit Lakes, and the state Department of Natural Resources is being accused of lax enforcement toward limiting the spread of the invasive species.

Boaters in the area were notified Friday of the discovery of Otter Tail County's Rose Lake by the Becker County Coalition of Lake Associations.

The association said that the zebra mussels' introduction to Rose Lake, part of the extensive Otter Tail River chain of lakes, most likely occurred because a boat lift was moved from a campground on nearby Lake Lizzie to property along Rose Lake, which is known among anglers for its northern pike, walleye, largemouth bass and bluegill fishing.

Lake Lizzie and several others in Otter Tail County are on the Minnesota Department of Natural Resources' (DNR) infested-waters list. State law requires that docks, lifts and other water-related equipment removed from an infested body of water can only be returned to that same body.

Hank Ludtke, the mayor of nearby Frazee and certified in invasive-species detection, said that the Rose Lake detection means the same will happen to the 87-mile Otter Tail River within the next few years.

"This is a battlefield," said Ludtke, who said he heard about the discovery during a recent Detroit Lakes Chamber of Commerce event, where the DNR was putting on an invasive species seminar. "How can we fight if the DNR isn't telling us we're at war?"

Luke Skinner, the DNR's supervisor for invasive species, said that Rose Lake's discovery was confirmed only on Wednesday and is so far confined to a single location involving young zebra mussels that are likely not reproducing.

That early stage of detection, Skinner noted, gives the DNR a rare opportunity to halt any spread from this discovery. He said preparations are being made for the DNR to treat the water with copper sulfate next week and kill off the zebra mussels.

The DNR said this is the first time that the agency will attempt to control a small, isolated population of zebra mussels in the state. After the treatment, the DNR added, Rose Lake will be put on a priority monitoring list and checked frequently for any more zebra mussels.

If zebra mussels are discovered next open-water season, the lake will be designated as an infested water, the DNR added.

"We're going to take real aggressive action," Skinner said in what he calls a case of "early detection and rapid response."

Terry Kalil, vice president of the Becker County Coalition of Lake Associations, said that one female zebra mussel "is capable of releasing 1 million juveniles in a single season, ruining a lake forever. This is a perfect example of why the DNR must get much more aggressive about containment of invasive species in infested waters."

Native to Eastern Europe and western Russia, zebra mussels were first discovered in Minnesota in 1989 in the Duluth harbor. Heavy infestations can kill native mussels, threaten fish populations and interfere with recreation.

The species has been found in many lakes in Minnesota, including Lake Mille Lacs along with recent discoveries in Brophy Lake and Lake Cowdry near Alexandria.

Paul Walsh • 612-673-4482