Big Cormorant Lakes Association

Big Cormorant Lakes Association
Becker County, MN

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Lake Learning - Aliens invading our lakes

	Green aliens are invading our lakes! These aliens are not from a different planet, but from different continents, mainly Eurasia. This article covers some common aquatic invasive plants, why they are harmful to our lakes, what the status is in this area and what you can do to protect our lakes. I'll start out by defining some commonly used terms. The terms "exotic", "alien", and "nonnative" can all be used to describe a species that does not naturally occur here, and has been brought here either accidentally or intentionally. In contrast, "native" plants occur naturally and are fully integrated into the ecosystem. Native aquatic plants are good and necessary habitats for fish, birds and other aquatic organisms. Not all alien plants are harmful, but those that are can disrupt the natural ecosystem, out-compete native plants and take over large areas. These plants are considered "invasive" and "nuisance" species. Invasive aquatic plants can get out of control because there is nothing in the ecosystem naturally to keep the population in check. When invasive plants take over a lake or wetland, the biodiversity in the ecosystem can decrease, meaning that there are fewer different kinds of plants and animals that can live there. When invasive plants form dense mats, they change the habitat and make it unsuitable for fish, birds and other aquatic organisms. The plants covered in this article are Eurasian watermilfoil, Curly-leaf pondweed and Flowering rush. For pictures, you can visit: http://www.dnr.state.mn.us/invasives/aquaticplants/index.html. With all these plants total elimination is probably not realistic, but lakes in the area keep the populations in check by spraying herbicides. To spray these plants, a DNR permit is required. The DNR has grants available for lakes to obtain funding for control of these plants, for more information visit: http://www.dnr.state.mn.us/grants/habitat/lakewide.html. Eurasian watermilfoil Eurasian watermilfoil is probably the plant you hear most about statewide. Luckily, it is not established in Ottertail or Becker Counties yet, so let's keep it that way! It is present in some lakes in Cass, Crow Wing and Douglas Counties, so we need to be vigilant. Once it is established, it grows in such dense mats that it is tough to swim and boat through. If you've ever been on Lake Minnetonka, you'll know what I mean. To prevent its spread make sure you check over your boat, trailer and propeller every time you put your boat in and take it out of the water. Eurasian watermilfoil can spread by a single segment of stem and leaves. There is a closely related native plant called northern watermilfoil. Northern watermilfoil has 5-6 leaflets per plant while Eurasian watermilfoil has 12-21 leaflets per plant. If you think you have found Eurasian watermilfoil, save a sample of it and report it to the DNR (1-888-MINNDNR). Curly-leaf pondweed Curly-leaf pondweed is a nuisance because it can form dense mats in early spring that interfere with recreation. When it dies off in June, it washes up in thick piles on the shoreline. It has wavy leaves with serrated edges and a flat, reddish stem. Curly-leaf pondweed is found in many lakes in the Detroit Lakes area and across the state. The map of MN on the right shows the distribution of Curly-leaf pondweed (MN DNR). Like Eurasian watermilfoil, it can spread from remnants of the plant left on boats. Most Curly-leaf pondweed infestations start at the public boat access and/or stream inlets from lakes upstream. It grows best in fine, silty sediment. Curly-leaf pondweed can be confused with whitestem pondweed, which has a more round green stem. Pelican Lake (Otter Tail county) has a Curly-leaf pondweed management plan that has been successful in controlling this invasive plant. The plan involves spraying once each spring (usually the week before Memorial Day) in areas of the lake where Curly-leaf pondweed is a problem. Spraying ranges from $400-480/acre and is done best using a professional applicator such as Minnesota Shoreline Restoration, Nisswa, MN. The chemical control program began in 2006, and over all there was an approximate 65% curlyleaf pondweed density reduction from 2006 to 2007. Flowering Rush Flowering rush was actually brought here intentionally because it has beautiful pink flowers. Flowering rush used to be sold commercially for use in garden pools, but now it is illegal to sell. Flowering rush was introduced into North America as an ornamental garden plant from Eurasia. It was first identified in Deadshot Bay (south bay of Detroit Lake) in the mid-1970s, and spread into the Big Detroit by the end of that decade. By the early 1980s it was found in many places around Big and Little Detroit; and moved down the Pelican River to Muskrat, Sallie and Melissa Lakes. This is the plant you can see prevalently at the Detroit Lakes city beach. The Pelican River Watershed District (PRWD) has a Flowering rush control plan and has been chemically treating the plant over the past two years. For specific information on their plan you can visit www.prwd.org or call 246-0436. Flowering rush on Detroit Lake's public beach Prevention Please be vigilant in the spread of aquatic invasive plants. Keep recreation on our lakes enjoyable and the lake ecosystem healthy. At boat landings, there are usually DNR signs telling which invasive species are present in the waterbody and how to prevent their spread. Never transplant aquatic plants that you haven't bought at a nursery and are unsure of what they are. For more information and pictures of these plants, visit: http://www.dnr.state.mn.us/invasives/aquaticplants/index.html. Moriya Rufer is the Lakes Monitoring Program Coordinator for RMB Environmental Laboratories in Detroit Lakes, 218-846-1465, lakes.rmbel@eot.com.