The Glen Lake/Crystal River Watershed is one of the Midwest’s most treasured natural places. Its iconic clear waters teem with wildlife and inspire summer vacations filled with swimming, boating, and fishing. But this beauty is at risk from Eurasian watermilfoil (EWM), an invasive aquatic plant that forms dense mats underwater and threatens the lake’s clarity and ecosystem.
Since first detecting EWM last year, the Glen Lake Association (GLA) has taken swift action to combat it. Early detection and rapid, science-based responses give us the best chance to stop this infestation before it becomes a significant problem.
Survey Results: High-Tech Monitoring Across the Watershed
This summer, GLA used an innovative, high-tech approach to survey the watershed for new EWM colonies. Contractors flew drones equipped with high-precision GPS technology known as real-time kinematic (RTK), which can pinpoint locations within two feet. They investigated 25 sites with suspicious plant growth across Big Glen, Fisher, and Brooks Lakes.
To supplement drone work, the team also deployed underwater remotely operated vehicles (ROVs). These provided 4K close-up imagery of the plant growth to assist in EWM identification.
The good news: no new EWM colonies were found.
Treatment Updates: Burlap Barriers in Little Glen
In collaboration with the Grand Traverse Band of Ottawa and Chippewa Indians, GLA continued monitoring and treating the EWM colonies discovered last year in the deep basin of Little Glen Lake.
All existing colonies remain covered with biodegradable burlap benthic barriers, a non-chemical method that blocks sunlight and kills the invasive plants. Several weeks after installation, staff used underwater ROVs to check barrier sites as part of routine maintenance. During this survey, they identified a few additional EWM strands. This was expected, since EWM can fragment easily and sometimes produces “runners” that grow out from the edge of barriers in search of sunlight.
Shortly after, a dive team from Freshwater Solutions, LLC secured a set of new micro barriers over the new strands. The site is now fully covered and will continue to undergo routine monitoring until the colonies are eradicated. As planned, the buoys marking treatment sites have been removed for the season.
How to Identify Eurasian Watermilfoil
Photo: Invasive Species Centre
EWM looks similar to native northern watermilfoil, but there are key differences.
- Limp leaves when removed from the water (native northern watermilfoil stays stiff).
- Feather-like leaves arranged in whorls with 12 or more thin segments (native has 11 or fewer).
14 to 24 leaflets per leaf (native usually has 14 or fewer).
- Depth range: commonly grows in 3 to 10 feet of water but can occur as deep as 33 feet.
- May have a reddish stem, though this alone is not a reliable identifier.
Want to learn more? Download MSU Extension’s Field Guide to Aquatic Invasive Plants.
How You Can Help
Walk and observe your shoreline this fall. If you spot a suspicious plant that looks like EWM:
- Take a clear photo.
- Note the wind direction at the time of discovery.
- Save the plant in a sealed zip lock bag, in case our watershed biologists want to take a closer look.
- Email both to rob@glenlakeassociation.org.
This information helps our team locate potential colonies quickly and accurately.
Support Our Work
Your donations and annual memberships make it possible to prevent, monitor, and eradicate EWM and other invasive species in the watershed. Together, we can keep it clear, healthy, and beautiful for generations to come.