Eurasian watermilfoil (EWM) aquatic invasive species beneath Lake Leelanau's surface water.

Lake Leelanau AIS Prevention: Early Detection/Rapid Response

One of the biggest challenges in controlling aquatic invasive species (AIS) is getting to them before they get out of hand. Removing AIS can be difficult when they lurk in the depths of the lake, unseen by most before it is (often) too late. That is why we need YOU to help us in our mission to detect AIS early so that we can respond rapidly. Please read our latest blog to learn how you can assist with Lake Leelanau AIS prevention and help protect and preserve our lake.

Early Detection/Rapid Response

Early Detection/Rapid Response is the name of the game. The earlier we detect AIS, the earlier we can respond and take care of these nasty invaders before they become a problem. We do our best with the newest technology to monitor our lake, but at any point, a boat could bring in invasive species that could take hold in Lake Leelanau.

Our biggest priority is ensuring that Eurasian watermilfoil (EWM)—which is being controlled in South Lake Leelanau—does not spread into North Lake Leelanau. That is why we need as many eyes on the lake as possible to help us detect EWM in North Lake Leelanau.

How to Identify EWM

The native milfoils (we are fortunate to have three native species in our lake) are an integral part of our ecosystem and should be differentiated from the Eurasian watermilfoil.

All milfoil species are submerged aquatic plants with leaves that are finely divided into leaflets. The most important difference is the number of leaflets (the thin leaves that come off the main stem). Native watermilfoil usually has 11 or fewer leaflets per leaf, whereas EWM typically has 12-21 leaflets per leaf. EWM tends to hang limp when out of the water, whereas the natives are usually more rigid.

EWM often has a reddish stem, but this alone cannot be used to distinguish it from its close, native relatives.

A graphic to compare Eurasian watermilfoil versus Northern watermilfoil.
Eurasian watermilfoil (invasive underwater plant) vs. Northern watermilfoil (native underwater plant)

Identifying Another AIS of Concern: Curly-Leaf Pondweed

Another AIS of concern in Lake Leelanau is Curly-Leaf Pondweed. It has been found the Narrows and in some water bodies neighboring Lake Leelanau. It has thin, dark green leaves with wavy “lasagna noodle-like” edges that are serrated (toothed) and a thick mid-vein running down each leaf.

Curly-leaf pondweed aquatic invasive species.
Photo courtesy of Leslie J. Mehrhoff, University of Connecticut (

Many other AIS are knocking on our door. Please use the following link to review other AIS of concern so you can take action if you spot one!

Michigan Watch List Aquatic Invasive Plants: A Guide for Identification

Reporting Form: Lake Leelanau AIS Prevention

Here comes the big question: What to do if you spot a plant you suspect is an aquatic invasive species? Please report it to us! LLLA has developed an easy-to-use digital form to submit findings if you suspect you have identified an AIS. If it looks like an AIS of concern, one of our biologists will contact you to investigate it further.


Click here to report any suspicious species!


Should you have any questions regarding Lake Leelanau AIS prevention, please get in touch with us at [email protected].

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