Underwater image of Eurasian watermilfoil in Lake Leelanau, Michigan.

Confronting Eurasian Watermilfoil in Lake Leelanau

The Lake Leelanau Lake Association (LLLA) team has been working hard this summer controlling Eurasian watermilfoil (EWM) in Lake Leelanau. This is a multi-faceted initiative that includes a lot of moving parts and helping hands. We invite you to learn about our progress and join us in celebrating the incredible EWM team and volunteers battling this invasive plant.

LLLA’s Mission

As you have likely heard, the most noxious aquatic invasive species (AIS) in North America, Eurasian watermilfoil, found its way into Lake Leelanau. Discovered in 2019, our multi-year control efforts began in 2020 to manage infested areas. EWM can grow up to the lake’s surface, choking out native plants and growing dense mats—making some highly infested areas impossible to swim in and drive boats through. 

To learn more about work done in previous years, please visit our Invasive Species page.

2023 Season Setup

Learning and fine-tuning from the past three years of control efforts, we set out for another impactful year of EWM control. At the beginning of the summer field season, our EWM team was better equipped than we had ever been in previous years. We were fully loaded with three boats that fit our unique needs, a full-time, seasonal technician to drive our boats and prepare materials, a seasoned crew of knowledgeable biologists, and more SCUBA divers than we had ever employed. 

At the end of the 2022 field season, we contracted Zero Gravity Aerial, LLC to perform a drone survey of the EWM in Lake Leelanau. This survey provided us with the precise locations of the EWM in the lake, from individual patches to large infestations. Using this information, we set out at the beginning of the season with a “plan of attack” for our fight against EWM with an artillery of tools. 

Field season is full of surprises!

In June 2023, our team set to work. We started with maintenance on some infestations covered in previous years using biodegradable burlap barriers. These barriers eliminate the plants’ ability to receive sunlight and photosynthesize, killing the plants below it. We have used these barriers in previous years, and have observed that native plants start to grow back from under the burlap within one year. The native plants have a seed bank, but EWM does not—it has not yet been able to grow to the surface and produce flowers. This is really encouraging for our work, as native plants can now take over the land previously infested with EWM.

At the beginning of the summer, we contracted Zero Gravity Aerial to take ortho-mosaic imagery of the largest remaining infestation located at Gordon’s Point on the east side of South Lake Leelanau. This produced a high-quality image of the infestation, allowing us to get a better size estimate of what we were working with. 

Much to our dismay, this infestation had apparently grown significantly since it was last photographed in the fall of 2022 or the drone survey did not have the resolving power to detect smaller and deeper plants around the perimeter. We observed this more and more in our work on different parts of the lake this summer. 

Anecdotally, we theorize that the low ice cover on Lake Leelanau this winter allowed more sunlight to reach EWM, extending its growing season. This invasive plant usually lies low under the dark ice and snow cover throughout winter, but without that, it was able to grow more than normal throughout the winter.

Summer 2023 Progress

Upon discovering the EWM had such a good winter, our team kicked it into high gear. Prioritizing the overgrown infestation at Gordon’s Point, we began setting burlap at a faster rate and larger scale than ever before! We set up to 32,000 square feet in a single day thanks to the help of many volunteers and crew. 

Our modified methods allowed us to set more burlap using divers, with more precise barrier placement. And even though the weather did not cooperate in the winter, we had very few rainy or windy days this summer, giving us ample time to work.

Thanks to our many helping hands and dedicated crew, we covered over 4 acres of EWM infestations so far this year alone. This accomplishment surpasses any previous year’s record by a significant margin. 

After four years of controlling EWM on Lake Leelanau, we are confident that two larger, previously treated sites are now EWM-free! This is a huge accomplishment for a plant that has proven to persist despite aggressive hand-pulling control efforts.

With a reduced crew, our work will continue through September as we continue to knock back the amount of EWM in Lake Leelanau.

LLLA scuba divers and volunteers use a boat to set burlap barriers to control Eurasian watermilfoil in Lake Leelanau, Michigan.
LLLA's EWM team members set large sections of burlap using a boat (left) and SCUBA divers (right).

EWM Research

In collaboration with the Grand Traverse Band of Ottawa and Chippewa Indians (GTB), our research partners at Grand Valley State University continue to take frequent samples of the water chemistry, macroinvertebrates, plants, and fish community on and off the burlap barriers. This research will continue through next year, with data likely available by the end of 2024—stay tuned!

Meet the EWM Team and Volunteers 

Although it has been a difficult and laborious summer, we have accomplished a great deal. This would not have been possible without the help and support of many. 

We extend our sincere gratitude to our EWM team members:

  • LLLA Lake Biologist, Ron Reimink
  • GTB Biologist, Dan Mays
  • SCUBA Dive Team Leader and Program Director, Annalise Povolo
  • Former LLLA Lake Biologist, Brian Price
  • Field Technician, Chris Froelich
  • SCUBA Divers Austin O’Connor, Catherine Dunn, Em Masterson, and Seamus Harrison
  • LLLA Stewardship Committee Chair, Lonnie Rademacher
  • GTB Technicians Josh Jackiewicz, Nathan Cambell, Cherrie McSwaby, and Sean Leask 

There are more volunteers than we have space to name. You know who you are, and we thank you for joining our fight this summer!

LLLA's EWM team and volunteers prep the largest burlap barrier to date for controlling EWM in Lake Leelanau, Michigan.
Nearly 20 volunteers assist with burlap preparations for one of the LLLA's largest burlap barrier sets to date!

Join the Fight Against Eurasian Watermilfoil in Lake Leelanau

We want to thank everyone who has helped support our work in controlling Eurasian watermilfoil in Lake Leelanau. Thanks to our supporters, we are getting bigger and better each year! However, our fight is still ongoing. 

If you are interested in contributing to our fight against EWM, we invite you to consider supporting the cause by donating or becoming an LLLA Member.

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