Our season of working on the lake is starting to wrap up, and we’re excited to share our progress with you in controlling Eurasian watermilfoil. Our field crew, in partnership with the Grand Traverse Band of Ottawa and Chippewa Indians, has been hard at work this summer to keep Lake Leelanau from being taken over by this pesky invasive species. Read about the successes and challenges of the 2026 season.
Signs of Success
After years of learning, adjusting, adapting, and improving, we are starting to see some real results in our battle against the invasive Eurasian watermilfoil (Myriophyllum spicatum). We begin each season by surveying and maintaining areas where we have previously laid biodegradable burlap to cover and kill Eurasian watermilfoil, or EWM. When we return to these sites, we are now finding little to no EWM in the area. This is a result of our constant learning and adaptation. We have learned that we need to cover slightly beyond the visible area of the EWM infestation, and in doing so, we ensure that no EWM that has been covered with burlap can creep out the edge to continue to thrive. By covering a bit beyond what we see, the burlap kills the EWM beneath it completely and results in fewer missed strands and less time needed for subsequent treatment and monitoring.
This overall decreasing trend is visualized below in a comparison of the amount of burlap set in the last four years in each region of South Lake Leelanau. As you can see in the figure, with the exception of the two regions in the southernmost section of the lake, where new infestations were discovered farther offshore from previously documented infestations nearby, this year all other regions saw a substantial decrease in the amount of burlap needed to cover the EWM in the lake.
Shifts in Scope of Work
The discovery of a couple of newer infestations in 2026 is partially due to having the capacity to spend more time scouting for EWM and less time actively covering it with burlap. In previous years, the majority of our time was spent laying burlap on very large infestations, some over 3.5 acres at one site - a very time-consuming task. With fewer large infestations, our crew is able to expand its search and start to transition from laying large amounts of burlap to searching for the "needle in the haystack."
Community-Based Monitoring MATTERS
Another reason for the discovery of some previously unknown infestations is our newly expanded Community-Based Monitoring Program! Originally launched as a pilot program in the North Lake to detect EWM if it ever reaches northward, lakefront property owners volunteer to scan their shoreline to search for any washed-up fragments of EWM. In 2026, we expanded the program to the South Lake to help us detect any undiscovered infestations, and it worked! So far this year, 18 reports came in of suspicious plants, 15 of which were native, but 3 of which were positively identified as Eurasian watermilfoil from the South Lake, which led to the discovery of a new infestation. We are happy to report that EWM has still not been discovered in North Lake Leelanau!
Thanks to all of our Community-Based Monitoring Volunteers! Your participation is a crucial component of early detection and rapid response! If you live on the lake and have not yet signed up for the program, click below!
Native Plants Reclaiming Their Territory
Other encouraging news is the continued observance of native aquatic plants growing on old burlap barriers. As our crew checks up on each previous year’s barriers, we seem to observe more and more native vegetation taking root either from their own fragments, their seed bank in the sediment, or from the spread of rhizomes (underground connecting root systems) from beyond the barrier. We are delighted to see some areas which previously were near monocultures of EWM now look like diverse native aquatic gardens like the photo below!
Great News, but the Threat is Not Over!
The indicators of success we have seen in recent years are wonderful for the efficacy of our method and for the control of Eurasian watermilfoil in Lake Leelanau. We are finishing this season with far less EWM left in the lake than in prior years, which, compared with the estimated 7-10 acres we started with, is an incredible feat. However, EWM is still present in the lake, and all procedures to prevent its spread are still necessary. Please don’t forget to:
- Clean, drain, and dry your watercraft (including personal watercraft) and dispose of any unused bait.
- Wash all parts of the boat, including trailers, anchors, fishing gear, life jackets, etc. Learn more about boat cleaning procedures here.
- Check your propeller for plants if you are going from the South Lake into the North Lake. Help us keep EWM out of North Lake Leelanau!
Not only are these procedures crucial to prevent the re-introduction of EWM (and to keep it from spreading from Lake Leelanau to other lakes!), but it is especially important as other threats creep closer to Lake Leelanau. Another aggressive aquatic invasive species, starry stonewort (Nitellopsis obtusa), was just discovered in Silver Lake in Grand Traverse County. Reports from the Benzie Conservation District show that there is frequent boater movement between Silver Lake and Lake Leelanau, making prevention measures even more important. Stay tuned to learn more about some of our new early detection techniques soon!
Thanks to Our Crew!
Last but certainly not least, we extend our heartfelt gratitude to our lake crew, who pour their blood, sweat, and tears into their work protecting Lake Leelanau from invasive species. We could not do this work in this short summer field season without many hands. Huge thanks to the LLLA staff, our partners from the Grand Traverse Band of Ottawa and Chippewa Indians (especially Dan Mays, Nathaniel Campbell, Josh Jackiewicz, and Cherrie McSawby), and all of the volunteers who contribute to our work! It really takes a village!
