Invasive aquatic plants spreading throughout state

University of Minnesota fisheries researcher Ray Newman and student on Christmas Lake in Hennepin County, Minnesota. He is looking for milfoil weevil, a promising biocontrol that eats invasive eurasian water milfoil. U of MN research of biological control of aquatic, invasive species. Minnesota Agricultural Experiment Station research project #41-074, “Trophic Relations in Freshwater Systems,” Principal Investigator Raymond M. Newman.

University of Minnesota fisheries researcher Ray Newman and student on Christmas Lake in Hennepin County, Minnesota. He is looking for milfoil weevil, a promising biocontrol that eats invasive eurasian water milfoil. U of MN research of biological control of aquatic, invasive species. Minnesota Agricultural Experiment Station research project #41-074, “Trophic Relations in Freshwater Systems,” Principal Investigator Raymond M. Newman.

Eurasian watermilfoil is one of many invasive species that found itself in the United States during the mid 21st century. A native of Europe, the species grows in dense canopies made up of hundreds of stems, each covered in between 12 and 21 leaflets. It’s often confused with the native northern watermilfoil that has only 4 to 9 leaflets.

It’s one of the most pervasive invaders in Minnesota’s inland lakes. The floating mats can crowd out native plants and can cause problems for boaters, fishermen and jet skiers. It first showed up in Lake Waconia in 1989. In Lake Minnetonka, the plant was first located in Excelsior Bay in 1987. It has since become a widespread issue on the lake, though there are ways to manage the species from a recreational standpoint.

The Lake Minnetonka Association (LMA) uses mechanical harvesters to cut the top five to six feet of the invasive plant, making it easier for boaters until it grows out once again. Another option that has more lasting effects is use of a coordinated herbicide initiative. This method has helped tremendously on areas of the lake like Gray’s Bay, according to LMA Executive Director Eric Evenson. He said they’ve see between 80 and 90 percent rebounding from native populations once the herbicides took effect to bring down Eurasian watermilfoil numbers.

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