Lake Minnetonka is the 9th largest lake in Minnesota and of the most popular among boaters, fishermen and recreationalists. However, the popularity doesn’t come without environmental issues. Invasive species such as curly-leaf pondweed, purple loosestrife, Eurasian watermilfoil and zebra mussels have been discovered as well as dealing with various sources of pollution which has affected water quality.
Lake Minnetonka has been a site for continuous research and management of aquatic invasive species. Many different management techniques are used. Allowing native bluegill populations to flourish may reduce common carp populations as they eat the carp larvae over the winter months, a copper –based pesticide proved positive in managing zebra mussels, flowering rush has been removed by hand pulling, beetles have been successful in controlling purple loosestrife, weed harvesters remove the mats of Eurasian watermilfoil and annual herbicide treatments reduced curly-leaf pondweed.
While northern watermilfoil is native to Minnesota, Eurasian watermilfoil and now hybrid milfoil (a cross between the invasive Eurasian watermilfoil and northern watermilfoil) is an invasive species. Researchers examining the status of this hybrid milfoil in Lake Minnetonka discovered hybrid milfoil are more prevalent in areas treated with herbicides than those areas with little management. This may suggest large scale herbicide treatments to control other aquatic invasive species could promote hybrid watermilfoil growth and some hybrids may show greater tolerance to treatment.
This just goes to show how various control methods may be required in order to maintain a balance between not only the various invasive species in a water body, but native populations as well.