Watch out, curly-leaf pondweed -- Lake Irene residents are coming after you

Lake Irene neighbors are planning an even more aggressive attack.

Curly leaf pondweed spreads via buds, shown in the jar at left, but it isn't the only aquatic invader found in Lake Irene. Property owner Larry Smith also brought samples of purple loosestrife and apple snails to the Aug. 21 annual meeting of the Lake Irene Preservation Association. (Karen Tolkkinen / Echo Press)

Lake Irene property owners say they want to put together a five-year plan that will allow them to aggressively pursue an unwanted, invasive weed that inhibits recreational use.

"The weed issue is the No. 1 issue," said Mike Kettler, one of four members elected Aug. 21 to the Lake Irene Preservation Association.

Residents have reported that curly-leaf pondweed has clogged up their boats and Jet Ski engines and prevented swimming near docks. At the association's annual meeting, they applauded loudly whenever anyone mentioned going after the lake and restoring the recreational use missing in recent years.

This spring, residents sprayed curly leaf pondweed on about 25% of Lake Irene's weed zone with an herbicide called Endothall. That knocked back the weed so much on the east side of the lake that residents say they could once again enjoy their lake. If the association comes up with a five-year plan to manage the weed, Minnesota will allow them to spray the entire weed zone, which amounts to about 240 acres of the 642-acre Lake Irene. Formally called the littoral zone, it's an area from 0-15 feet depth where weeds grow.

Spraying the entire weed zone will help boaters and swimmers around the entire lake. Property owners who don't want the water in front of their land sprayed can opt out of the plan.


Curly-leaf pondweed has been in Minnesota waters for so long that the state doesn't even include it on its list of infested waters. It probably arrived in Minnesota in the 1880s with the introduction of common carp as a gamefish, aquatic invasive species specialist Mark Ranweiler of the DNR told about 70 people who attended the Saturday meeting. It was first observed in Minnesota in the early part of the 20th century, and is found in 40 Douglas County lakes, he said.

Known for its skinny, lasagna-style leaves, the plant recently has grown aggressively in Lake Irene.

In fact, it grew so abundantly in many places in Lake Irene that it amounted to a monoculture, driving out native aquatic plants, Ranweiler said. The tables were turned this spring, he said, as the spray killed off the curly-leaf pondweed and native plants such as coontail and bullrush rebounded. Lake Irene has native water lilies that must be protected, he said.

Native plants also impede recreation, but not as bad, local residents said.

Multiple conditions have led to a proliferation of weeds in area lakes this summer. Warm weather arrived earlier in the year, expanding the growing season. Also, the drought led to shallower lakes, and invasive zebra mussels have created clearer water, allowing sunlight to penetrate.

Ranweiler told the lake association that if it wants to spray more than 15% of its weed zone, that it must have a Lake Vegetation Management Plan in place before 2022.

He also said no matter how aggressive the lake association gets, it will likely always have to contend with curly-leaf pondweed.

"One hundred percent eradication is not a reasonable goal," he said.


Weed control can be expensive, and lakeshore owners generally have to foot the bill themselves, although in 2021 they received a grant from Douglas County to help.

"Even if we didn't get the grant money, it would be worth spending the money to get rid of curly leaf pondweed," resident Bob Strawn told the crowd, and everybody applauded.

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