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CLWA plans treatment of invasive Eurasian watermilfoil

The CLWA’s comprehensive three-year (2016-2018) survey of the aquatic plants in Crystal Lake revealed a generally healthy lake, and identified Eurasian watermilfoil (“EWM”, Myriophyllum spicatum) as the only invasive plant species currently present. The invasive here is limited in extent – just 6.05 acres of Crystal Lake’s total area of about 10,000 acres, primarily in the east end. The CLWA is proposing treatment at this time in order to halt the spread. Most authorities recommend treatment before it reaches an advanced stage where control becomes impossible.

EWM is widespread in Michigan and Crystal’s situation is much better than many lakes in the state. The highest density is found at the entire drop-off surrounding the Beulah village boat launch, where it was likely originally introduced by itinerant boats. There is intermittent colonization along the southeast shore up to and past the DNR launch and around Railroad Point into Onkeonwe Bay. Additional colonies are established at the Lobb road-end launch but none west of the Disciples of Christ Conference Center on South Shore Rd. The west end and north shore appear to be virtually EWM free. DNA analysis shows that Crystal’s milfoil fortunately has not yet hybridized into variant species for which effective treatments are not available.

None of these colonies has yet begun to interfere with recreational activities, but left unchecked, EWM can out-compete native beneficial plants, and overwhelm all other lake biology including fish and amphibians. It can grow so thickly that it requires mechanical harvesters to clear the top few feet of water for a short period of time before it grows back, interfering drastically with recreational boating, swimming and fishing.

After thorough investigation of all available treatment methods, CLWA has determined that treatment with chemical herbicides is the most cost effective and suitable one for the existing conditions on Crystal Lake. The most widely used treatment, it is quick and has proven successful in controlling (but not totally eliminating) the invasive plant.

Effective treatment usually requires two treatments per year in our climate. Monitoring results over time will be needed and there are many lakes that have a regular program for control. The specific agents used for EWM, 2,4-D or Triclopyr, do not affect the native plants or animals of the lake.

CLWA’s experience collaborating with aerial drone photography has proven to be highly successful, as the aerial supervision insures highly accurate placement and potential less use of the chemical product. We propose that method for Crystal Lake.

The use of herbicide in inland lakes requires permits from the Department of Environment, Great Lakes and Energy (EGLE), a licensed professional applicator, and the permission of involved landowners. The CLWA will soon be approaching affected riparians to explain the proposal and answer any questions.

If the required permits can be obtained in a timely fashion, the CLWA hopes to begin treatment in the summer of 2020. CLWA will pay costs, estimated at up to $10,000.

The CLWA Aquatic Weed Survey was led by CLWA board member Jim Hamp, assisted by the drone technology of Zero Gravity Aerial, and conducted under the auspices of the Michigan Cooperative Lakes Monitoring Program. The identification and control of invasive species has been a long-time concern of the CLWA, leading to the construction of the boat washing station at the Mollineaux Road launch site in 2013.

For more information on Eurasian watermilfoil, its threats and treatment, see the following sources:

Michigan Invasive Species: Eurasian Watermilfoil

State of Michigan’s Status and Strategy for Eurasian Watermilfoil Management (DEQ)

Weed Risk Assessment for Myriophyllum spicatumL.(Haloragaceae) – Eurasian watermilfoil (Michigan Department of Agriculture