The Lake Minnetonka Conservation District has forged a two-pronged approach to fight Eurasian milfoil and other pesky weeds: mechanical cutting in some areas, and herbicides in certain bays.
A district subcommittee recommended the strategy after studying the drawbacks and effectiveness of both methods, and is holding a meeting Wednesday night to get public feedback.
The main troublemaker, Eurasian water milfoil, began invading the lake in 1987. It can form huge mats that clog channels and boat motors, ruin water sports such as waterskiing and sailing, out-compete native water plants, and wash up along shores to create a cleanup nuisance.
Milfoil will never be eradicated, nor will curly-leaf pondweed, another non-native plant that bedevils Minnetonka and many other lakes.
The district makes decisions about the lake and spends tax money levied from the 14 communities that surround it and are represented on its board.
To keep the weeds under control, the district spends about $95,000 annually -- one third of it from a Minnesota Department of Natural Resources grant -- on "mechanical harvesting." Three floating paddlewheel harvesters roam the lake from mid-June to mid-August, zeroing in on the worst areas to chop and collect boatloads of soggy milfoil and pondweed.
Under the subcommittee plan, the harvests would continue. "It would be the main way to manage milfoil on the lake," said district Executive Director Greg Nybeck.
The proposed plan also recommends using herbicides to kill the plants. Chemicals have been used with some success in a five-year demonstration project, mainly in Carman, Grays and Phelps bays.
The subcommittee recommends that five other bays are also suitable for herbicide treatment on an as-needed rotating basis, with perhaps two to four of them getting the chemical doses each year. They include St. Albans, St. Louis, Carsons, Gideon and North Arm bays.
Herbicide treatment stands a better chance of succeeding in those areas, the report said, because the bays are somewhat sheltered from the larger open waters of the lake.
The recommendations do not estimate costs of a future herbicide program. They also don't specify who would pay for it, or who would manage the program. Those and other items will be part of the public discussion, Nybeck said. However, all such work with chemicals in lakes requires DNR permits and oversight, he said.
The Lake Minnetonka Association, a non-profit group representing lakeshore owners and businesses, managed the five-year herbicide demonstration project from 2008 through 2012.
Nybeck said the conservation district has not allocated any money for herbicide treatments in 2013, but it might be able to budget up to $75,000 annually in future years if additional funds from other sources become available as part of a public-private partnership.
He said the district will use this week's public comments as it prepares a final plan for adoption, probably next month.
Tom Meersman • 612-673-7388