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Lake’s efforts to control curly leaf pondweed make for happy days on the water


About the time that anglers are happily tossing slip-bobber rigs to sunfish in the shallow waters of Nest Lake’s northeast corner, the hard work begins. Starting usually in May, sometimes in late

April, workers begin plying the waters of Nest Lake in two mechanical harvesters. They have about two months to cut and remove curly-leaf pondweed.

The non-native, aquatic plant infests roughly 750 acres of the lake’s 1,050 acres.

When it was not harvested as extensively as now, the invasive plant would grow into mats dense and thick enough to effectively prevent boating and swimming in whole sections of the lake.

And every year, all of the curly-leaf pondweed would begin to die-off in early July. The decaying plants released the phosphorus they held, and triggered massive, pea-soup like blooms of algae.

In turn, there were some years when the dying algae blooms created problems of their own. Several years ago crappies began dying by the thousands in the oxygen starved waters, a result of the microbes feeding on the decaying algae.

 “Tremendous, negative impacts on the lake,” said Brian Nelson of the curly-leaf pondweed.

Nelson, a director with the Nest Lake Improvement Association, is among those who will be recognized in an awards ceremony Tuesday. The Middle Fork of the Crow River Watershed District is recognizing the lake association’s work as its first “project of the year.”

Last year, the lake association removed 5,500 cubic yards of curly-leaf pondweed from the lake, more than double the amount of the previous year. A largely snow-free winter and early season rains that washed nutrients into the lake created the perfect storm of conditions to produce a bumper crop of the plant.

Yet thanks to the aggressive harvesting, recreational boating, swimming and fishing continued through the summer, in waters that remained fairly clear. The lake remained “useable,” said Nelson, and people were still tossing bobbers in late August, and happy because of it.

Curly-leaf pondweed infests over 700 lakes in the state, and severely hampers recreational activities in many of them.

Nest Lake offers fertile waters and territory for the plant. The Middle Fork of the Crow River carries a steady flow of nutrients to the lake. Large areas of the lake fall within the three- and 10-feet depth preferred by the invasive.

But after seeing last year’s success, Nelson and others are optimistic that Nest Lake can turn the corner in a strategy to control the invasive.

Nest Lake is among one of the very few to have created its own taxing district to provide the resources to control the invasive plant. Previously, a group of residents on the north shore kept a small harvester to keep open paths to their docks.

Today, the lake association has a budget of $45,000. It hires two workers to operate the harvesters to clear cut as much of the plant as possible before it produces and releases the turions or buds that seed the next year’s crop.

It also purchases herbicide to knock down curly-leaf pondweed in a 40-acre patch on the lake’s north side.

The lake association otherwise depends entirely on volunteer work for its efforts. The volunteers worked first to build support among lakeshore property owners to tax themselves for the benefit of all who use the lake.

The lake association gets a lot of bang for its buck, thanks to the work of the volunteers. Its biggest harvester was purchased second hand in Wisconsin for $25,000, as compared to $140,000 for a new unit. Nelson provided the semi-truck and another the crane needed to launch the machine on the local waters.

Unlike many lakes troubled by curly-leaf pondweed, Nest Lake has retained a healthy population of native aquatic plants, according to Nicholas Brown, and invasive species specialist with the Minnesota Department of Natural Resources. He said the local association members also understand the importance of protecting the native plants, which provide the habitat needed for the game fishing opportunities the lake provides many.

 “Leave the good stuff, cut the bad,” said Nelson of the harvesting strategy.

An improved Nest Lake also means the waters remain clear downstream in Green Lake. Nest Lake’s aquatic plants serve as filters to capture nutrients that would otherwise flow to Green Lake.

Brown said it can be difficult to keep curly-leaf pondweed under control on a consistent, year-to-year basis. The plant crowds out native vegetation by starting its growth in January, under the ice. It also grows in extremely dense stands.

Seasonal control efforts such as herbicides and harvesting help, but it is also extremely important to take a watershed approach, he noted. Controlling the amount of nutrients reaching the lake and improving water quality can go a long ways towards helping native vegetation compete with the invasive, he explained.

That’s very much the goal of the Middle Fork of the Crow River Watershed District, according to Chad Anderson, administrator of the Middle Fork of the Crow River Watershed District.

He said the watershed is working with the City of New London to limit the nutrients from lawns and streets that are flushed into the river by the storm water system during rain events. It is also working with upstream landowners to hold soil and water on the landscape.

 “It’s always better to prevent than fix,” said Anderson. “A lot less headache, a lot less expense.”

And in this case, a lot more swimming, boating and fishing.

Tom Cherveny

Tom Cherveny is a regional and outdoor reporter with the West Central Tribune in Willmar, MN.

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