Aquatic plants & animals

Aquatic plants and animals are critical to environmental quality and the quality of life for all Minnesotans. Ecological Resources staff provide a variety of services to support the continuing vitality of these resources through programs, publications, and other resources.

Aquatic plants and animals questions & answers

I got swimmer's itch! Where does it come from and what can I do to keep from getting it again?

The DNR has prepared this advice for avoiding or treating swimmer's itch.

How do I get rid of the green scum on my pond?

The "scum" is probably either filamentous algae or duckweed Duckweed can be removed by skimming or applying a DNR-approved herbicide. Filamentous algae is composed of long, green threads-often matted together, resembling green cotton. The "scum" could also be a severe bloom of plankton algae that has floated to the surface. Filamentous algae can be controlled with copper sulfate or other copper-based algicides. A bloom of plankton algae occurring at this stage is a sign that the algae is dying; the bloom will break up by itself.

How do I know if the green scum is a floating plant or algae?

Can it be swept aside with your hand? If it can, and it looks like green, oval seed-like plants 1/8- to 1/4-inch in diameter, it is likely duckweed. If it looks like green cornmeal, it is probably watermeal. If it cannot be swept aside with your hand and it is stringy, hairlike, or slimy or colors the water green or brown, it is likely algae.

Do I need a permit to use a WeedRoller?

Automated untended aquatic plant control devices (such as the Crary WeedRoller) have the potential to remove larger swaths of vegetation, displace more sediment, and eliminate plants for a longer period of time than many other devices used by homeowners to control aquatic plants. For these reasons, it is important to ensure that the device is used appropriately. The Minnesota regulations state that:

1. A permit is required to use Crary WeedRollers, and similar devices, for aquatic plant control regardless of the size of the area. A permit will likely not be issued where operating this device is expected to "dredge" or excavate the lake bottom.
2. A permit valid for three years may be obtained if the device is operated in an area of submerged vegetation that is no larger than 2,500 square feet, and extends no more than 50 feet along the shore or one-half the property owner's frontage, whichever is less. An annual permit is required for larger areas.

For more information, contact your Area or Regional Fisheries Office or the Ecological Resources Division's Aquatic Plant Management Program.

What can I do to control plants around my dock and lakeshore? Do I need a permit?

Measures such as cutting, pulling, or using herbicides can control aquatic plants from season to season. But in the long run, the best way to combat excessive growth of aquatic plants is by maintaining high water quality through preventative actions such as:

• stopping the introduction or spread of undesirable exotic plants (such as purple loosestrife, curly-leaf pondweed, and Eurasian watermilfoil);
• minimizing hard surfaces (roads, roofs, pavement) close to the lake that increase the amount of nutrient-rich or contaminated runoff entering the lake;
• reducing the flow of nutrients into the lake (such as lawn fertilizers, grass clippings, failed septic system wastes, high phosphorous detergents, pet and livestock wastes); and
• preventing sediments (such as eroding soil from bare shorelines) from entering the lake.

For more information about improving water quality on your shoreland see the Division of Waters' Guide for Buying and Managing Shoreland.

If you believe the growth of aquatic plants near your shoreline creates a nuisance, refer to the flowchart of The Permit Process: An Overview on page 17 of A Guide to Aquatic Plants to help pinpoint the steps necessary for appropriate control options.

Does the DNR have any funds available to help me control the aquatic plants?

Most often, we do not. The only aquatic plant control efforts funded by the DNR are for the exotic species purple loosestrife and Eurasian watermilfoil. Invasive Species Programs.

Where can I get printed information on aquatic plant management and identification?

The DNR would be happy to send you our Aquatic Plant Management information materials. Please check the Aquatic Plant Management Program publication page, then follow the link to Request Publication, or contact a regional Fisheries office.