Shoreline Ecology

Weed Control Starts at Home

The principal threat to Lake Mitchell’s water quality comes from phosphorus, nitrogen, and sediments. While they are naturally occurring elements vital to maintaining living organisms in our lake, excess amounts of phosphorus, nitrogen, and sediments wreak havoc on the balance of life.

To increase weed growth in our lake use fertilizers containing phosphorus and nitrogen on your lawn. Rain, lawn sprinkling, and snow melt all will wash fertilizers and sediments from yards into the lake unless there is a substantial greenbelt along the shoreline. The soil in the Lake Mitchell watershed generally has more than adequate amounts of phosphorus and nitrogen to grow lawns. If you take a soil sample to the Michigan State Extension Office in Cadillac, they will test your soil to determine what, if any, fertilizers are needed. If you must use fertilizers select bags that are phosphorus-free and with slow release nitrogen. If the label on the package has a zero in the middle such as 12-0-20 then you know it contains no phosphorus.

The degradation of lakes caused by phosphorus has attained national attention with several states regulating the use of fertilizers containing phosphorus. Cherry Grove and Selma Townships both have passed resolutions recommending that fertilizers on lakeshore properties be phosphorus-free. The City of Cadillac now uses only phosphorus –free chemicals on its lakefront property.

A greenbelt is a band of natural vegetation growing along a lake shoreline. Greenbelts slow surface runoff before it enters the water, allowing sediments, excess nutrients, and other pollutants to settle out. Uncontrolled sedimentation will alter the habitat of crayfish, mayfly larvae, and fish as well as increase phosphorous loads in the lake. Leaving a strip of natural vegetation between your lawn and the water’s edge is one of the best things you can do to maintain our lake’s water quality.

Standing on a seawall and watching the waves rebounding off, you note that the turbulence stirs up the water and bottom sediment. The US Fish and Wildlife Service notes that "Shallow waters provide nursery habitat for fry and young-of-the-year fish and habitat for a greater variety of animal fauna than for all other aquatic zones." In other words, the shallows of inland lakes are the most biologically productive areas. Seawalls, especially those with little or no rock riprap, create virtual "biological deserts." Natural materials are preferred where actively eroding shoreline justifies protective measures. Construction should follow the natural shoreline contours and minimize the use of steel, wood, or vinyl. Flat or corrugated material reflects almost all of a boat wake’s wave energy back into open water accentuating erosion. If a straight-sided seawall is in place, it should be faced with riprap. Rock riprap is generally more effective at dispersing wave energy and costs substantially less than wood or steel seawall. If rock riprap is used as a seawall, it should be placed over a geo textile material to keep soil from flowing through the seawall.

A ¾ acre patch of Phragmites, an invasive plant, also known as the common reed is growing in Big Cove where the Camp Torenta Canal enters the lake. The Lake Mitchell Improvement Board has budgeted $1000 to chemically treat this patch. Sometimes sold as ornamentals, these plants often are found in gardens and yard vegetation. This wetland grass grows from six to fifteen feet tall and thrives in lowland areas, roadside ditches, and along shorelines. The plant grows in dense stands and crowds out other beneficial native wetland vegetation. If you think you have found phragmites, please contact the Lake Mitchell Improvement Board.

If allowed to spread into a wetland, phragmites can become the dominant plant and prove harmful to animals, birds, fish and amphibians that reside in these lowland areas. The plant spreads by fragmentation and its extensive root system makes it difficult to control. Phragmites has flat green leaves that alternate along the stem and a distinctive purple-brown seed head with plumes that appears in late July. Phragmites can be controlled using herbicide treatments followed cutting or mowing. There is currently no biological control of phragmites.

The Lake Mitchell Improvement Board has allocated $5000 from its 2010 budget to purchase Galerucella beetles which eat purple loosestrife. The beetles will be planted in Big Cover where purple loosestrife, whose beautiful, but unwanted magenta flowers create a real threat to the health and survival of that wetland shoreline.

Wetlands are the most biologically diverse productive component of our ecosystem. Numerous species of plants, birds, mammals, reptiles, insects, fish, and amphibians rely on healthy wetlands for their survival. However when purple loosestrife gets a foothold, the habitat where fish and wildlife feed, seek shelter, reproduce and raise young, quickly become choked under a sea of purple flowers.

Loosestrife plants are also found in other parts of the lake and occasionally in gardens. If you know of loosestrife plants, they should be destroyed. To remove plants, dig out the root system and then place the entire plant in a plastic bag so as to not spread the seeds which can be shaken off the flowers.

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