A healthy and diverse population of native aquatic plants is essential to good water quality and a healthy lake. Responsible for protecting that population, MN DNR carefully regulates activities that may threaten that population.
A Bit of Detroiter Aquatic Plant History
Aquatic Plant (“weed”) problems and control are not new to Detroit Lake. In 1949 Lake Detroiters was founded in part to deal with “algae and weed control” on Big and Little Detroit. In 1950 a Detroiters committee looked into the possibilities of “weed spraying”, and in 1952, another committee was formed “to study dredging as a means of weed and algae control”. In 1953 there was association interest in renting a weed-cutting machine, and for three years (1954-56) LDA sponsored applications of sodium arsenite to portions of the shoreline for purposes of weed control. In the late 1950’s copper sulfate was purchased by the Association and made available to members for control of weeds and algae.
Large scale aquatic plant harvesting by the Pelican River Watershed District began on Detroit Lake in the late 1980’s. The costs of that program were borne by assessments on shoreline property owners. The program’s focus was towards dense stands of invasive species, especially Curly-leafed Pondweed and Flowering Rush with the intent to reduce interference with recreation and to offer some control of their spread. The removal of such plants by mechanical harvesters reached a peak of 1800 tons in 2002, after which changes in DNR policies and the realization that harvesting was ineffective in Flowering Rush Control (even contributing to its spread), led to a rapid decline in machine harvesting.
Not coincidentally, PRWD began experimenting with chemical treatments in 2003, after which mechanical harvesting was gradually reduced and then abandoned altogether by 2009. The chemical experiments, which involved application timing, and amounts, included research by the US Corps of Engineers, together with evolving state treatment policies, as well as new funding arrangements, led to the successful implementation of lake-wide chemical treatments. These quite rapidly reduced flowering rush populations, and curtailed curly-leafed pondweed. Successful chemical treatments have resulted in a reduction of their use.
Aquatic Vegetation in Detroit Lake
Comparative information with other lakes, and over time does not exist. PRWD conducted a detailed survey of vegetation of Detroit Lake in 2019 which showed the presence of 20 different species, including Chara, Common Bladderwort, Northern Watermilfoil, Water Celery and Water Moss as the most common species. As to general distribution factors on the lake, it was noted that as dock density increases, species diversity and density decreases. Vegetation density and diversity also was generally lower in Little Detroit, presumably because of its shallowness and heavy recreation activity. On Big Detroit’s North and West shores, and near Long Bridge, density and diversity was higher.
As a part of its continuing treatment protocols, the District also routinely maps known locations having known remaining concentrations of Fflowering Rush and Curlyleaf Pondweed.
What can a lakeshore resident do about aquatic plants?
Without a permit, to have a swimming or boat-docking area, a lakeshore owner may…
· Cut or pull submerged vegetation in an area no larger than 2500 sf. and not extending more than 50 feet or ½ length of owned shoreline (whichever is less).
With a permit, lakeshore owners may
· remove emergent vegetation (e.g. cattails, bulrushes)
· hand or mechanically remove submerged vegetation in an area larger than 2500 sf.
· Apply herbicides or algaecides
· Move free-floating bog
· Transplant plants into the lake
· use automatic aquatic plant control devices
· remove floating-leaf vegetation in a channel wider than 15 feet
Lakeshore owners are not allowed to:
· Excavate lake bottom, use hydraulic jets, lake bottom barrier,
· Remove aquatic plants from posted fish-spawning areas, from undeveloped shoreline, or where plants do not interfere with swimming or boating.
For more details, see the website link below, or a lakeshore owner may contact a DNR Aquatic Plant Specialist at (218)-308-2623. Also Permits may be obtained on-line. Permit fees generally run about $35.
For those contemplating using herbicides for plant control, consider a Licensed Pesticide Applicator (such a person may also secure the appropriate permit). A list of LPA’s is included at the website below.
https://www.dnr.state.mn.us/shorelandmgmt/apg/regulations.html
RDH, July 2024
