According to Nick Brown, DNR invasive species specialist, herbicides used to treat curly-leaf pondweed on Minnesota lakes may not lead to improvements in water quality.
Curly-leaf pondweed is an invasive plant found throughout much of Minnesota. The plant grows slowly throughout the winter under the ice, but once the ice has left the lake the plants start to grow very rapidly. Curly-leaf pondweed gets a jump start on native aquatic plants, leading to dense mats on the surface by May or June. Sometime around mid-July, curly-leaf pondweed dies off and decomposes in the lake.
In the past, many lake managers thought that early treatment of curly-leaf pondweed might lead to better water quality and improved native plant populations. However, recent research has proven that large-scale treatments in lakes with high nutrients levels did not produce water quality benefits or increase native plant populations.
Herbicide control is restricted to 15% of the littoral area of the lake, but mechanical harvesting allows for up to 50% of the littoral area of the lake to be harvested. A combination of both methods may be used as well. A limit on what areas to be treated or harvested ensures that native plants, which provide water quality and fish and wildlife habitat benefits, will be protected.