The DNR is taking step one to eradicate the exotic,
highly invasive aquatic plant hydrilla from Lake Manitou.
Approximately 20 acres of water will be treated with the aquatic
herbicide Komeen September 13, weather permitting. Specifically, the
bay between Coney Island and the City boat ramp plus an area around
Poet’s Point will be treated. These are the locations with the
highest density of hydrilla. Scattered plants are in other areas of
the lake.
The lake is the only known location of hydrilla in the Midwest.
Its presence was confirmed in late August.
Experts from Southern states and California, who have been
dealing with hydrilla for decades, recommend that the species be
treated with herbicides as a first step toward long-term
eradication.
Hydrilla advances in a number of ways. During fall, the plant
produces an abundance of propagules, which are reproductive
structures that allow it to survive over the winter. A rapid
elimination of the lake’s hydrilla now will therefore reduce the
“seed source” for next year’s growth. Funding for this rapid
response hydrilla treatment will come from the DNR Lake and River
Enhancement (LARE) program.
During a Komeen application there are no water-use restrictions.
Swimming, irrigating, and other water uses can continue as usual.
DNR is considering boat-use restrictions to contain the plant.
None are yet in effect. In the meantime, boaters using Lake Manitou
can help ensure that hydrilla isn’t moved elsewhere. After boaters
load their boat on a trailer, but before they leave the access ramp,
they should remove all plant material and dispose of it in the
trash. Common places to find plant fragments include boat trailer
bunks, rollers, axles, and fenders. Plant pieces are also found on a
boat floor or propeller.