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European frogbit (Hydrocharis morsus-ranae, NR40 Prohibited Species) has now been found in Brown and Door County.
BACKGROUND — European frogbit was first discovered in the wild in Wisconsin late last summer and the known general extent at that time ranged from the City of Marinette to the City of Oconto. Additional monitoring by Oconto and Marinette County Land and Water Conservation Department staff have found additional populations within and beyond that range reaching all of the way to the Oconto/Brown County border. The only other finding of this species in Wisconsin prior to 2021 was in 2018 at a nursery in southern Wisconsin; however, it has become widespread along the coastal areas of lakes Erie and Huron up to the eastern Upper Peninsula which are the closest known populations.
BROWN & DOOR COUNTIES — Myself and AIS Specialist, Mandy Mellinger, observed the Brown and Door County plants during early detection monitoring as part of the Green Bay European frogbit response effort. The Brown County plants were found along the interior coastal wetlands of Little Tail Point. The Door County plants were found in the Keyes Creek area of Little Sturgeon Bay. In both instances, the plants were small, sparse, and were easily removed. The plants will be pressed and submitted to the Wisconsin State Herbarium. It is likely that these plants drifted in from established populations via currents or sprouted from a hitchhiking turion (overwintering bud).
NEXT STEPS — The European frogbit Response Team worked diligently over the winter to write a management plan that helps to inform much of the work ahead including monitoring, decision making, prioritization, funding, etc. as outlined in the Department’s Response Framework. A press release will likely be issued once we learn more about whether there are established populations and the general extent.
HOW YOU CAN HELP —
- Please take a few minutes to familiarize yourself with the identifying characteristics of European frogbit by visiting the species webpage. Additional resources can also be found on Michigan’s Invasive Species Program webpage.
- Keep a close eye out for it during your fieldwork – it likes shallow, quiet or slow-moving water; edges of lakes, rivers and streams; swamps, marshes, and ditches.
- Consider highlighting the species at upcoming outreach events. Species watch cards are available in the AIS Publications and Products Catalog. To order, call (608) 266-0061 or email [email protected] and ask for item WT-754.
- Think you found some? Take detailed photos and collect a sample, if possible. Keep the sample in a plastic bag with water. Note the location and email [email protected] or call/text 920-883-5041.
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