Invasive Milfoil Is Taking its Toll on Minnesota Lake Communities

Published August 1, 2008

The Land of Ten Thousand Lakes is quickly becoming the Land of Aquatic Devastation as noxious Eurasian milfoil spreads rapidly across the state.

On June 18, the Minnesota Department of Natural Resources reported the invasive plant has been found in Upper Mission Lake, about 15 miles north of Brainerd. This brings the number of infested Minnesota lakes to 205 and growing.

Student Essay Describes Harm

Not only is milfoil despoiling Minnesota lakes, it is also having an unexpected effect on Minnesota’s culture. Todd Frie of Osakis won second place in the Douglas County Soil and Water Conservation District “water wisdom” essay contest by describing the negative effects of milfoil on area lakes and communities. Frie’s description of negative milfoil effects won him a college scholarship.

Frie noted milfoil takes root in lake sediment and then “quickly grows to the surface and forms a canopy that shades out the other beneficial native plants. It reproduces extremely rapidly and can infest an entire lake within two years of introduction to the system.”

Milfoil, observed Frie, “has many impacts on our lakes. It has less value as a food source for waterfowl than the native plants it replaces. Because it grows so quickly and becomes very dense, small fish have a very high survival rate. However, the larger fish cannot get through easily to get their prey.

“Thick growth of milfoil also degrades water quality by depleting oxygen levels. The thick beds also restrict recreational uses like swimming, boating, and fishing. They give the appearance that the lake is ‘dead,'” Frie noted. “These thick mats can also cause flooding and they create good habitats for mosquitoes. They can also clog water intakes and result in rotten mats that end up lying on the beaches, which takes away from the natural beauty of the beach.”

Lesson from Idaho

As Minnesota communities search for answers to the rapidly spreading milfoil, communities in Idaho offer a roadmap of effective treatment.

Since 2006 the Idaho legislature has allocated funds to battle the milfoil that had been ruining state lakes. Aggressive chemical treatments have successfully eradicated milfoil while leaving native plant and animal species unaffected.

After two years of success with chemical treatments, Bonner County, Idaho launched its first treatments of the year on June 23. The targeted herbicides have dramatically reduced the extent of invasive milfoil. This summer some lakes in the county are being treated for the first time, while some that have been treated in the past will be given smaller amounts of the chemicals to prevent recurrence of the milfoil.

James M. Taylor ([email protected]) is a senior fellow of The Heartland Institute and managing editor of Environment & Climate News.