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Update on Eurasian Water Milfoil

Eurasian water milfoil (EWM) was first identified in Cobbosseecontee (Cobbossee) Lake in 2018, however, the aggressive weed has since spread to 7 new locations, including the Winthrop Public Boat Launch and Cobbosseecontee Stream. Due to the escalation in spread and the close proximity of the current infestations to the Belgrade Lakes Watershed, we are asking our members to keep a watchful eye on the water for any unusual looking plants.

Like all “milfoils” EWM has fine feather-divided leaves. EWM can be distinguished from native milfoils and invasive variable leaf milfoil by the number of leaflets (little hairs on the leaf stem) and the large internodal space between leaves.

Comparision of various milfoil species. Image source:

Like many invasive aquatic plants, EWM is native to parts of Europe, Asia, and Northern Africa. EWM was first transported to North America in the early 1900’s, most likely by ballast ships. This noxious weed has taken over entire lakes in the Midwest, where the water alkalinity and lack of natural predators have enabled the plant to grow out of control. Watch this short film to see how one lake in Minnesota, which happens to be a waterbody of deep importance to 7 Lakes board member Lynn Matson, has been ruined by Eurasian water milfoil Lynn remembers when the lake was a pristine ecosystem, where he spent many weekends as a youngster and had the privilege to share his childhood memories with his own daughters, teaching them how to swim and sail. He is heartbroken to see the current state of the lake. “Weed harvesters” patrol the lake on an annual basis, ripping up weeds by the thousands just to clear paths for boats to navigate. Our team at 7 Lakes and our neighbors at Friends of Cobbossee Watershed, will continue to do everything in their power to keep Maine lakes free of this noxious weed. Learn more about Friends of Cobbossee’s fight here

Spread of Eurasian water milfoil across the country since the 40's. Source:

Sharon Mann,

Invasive Aquatics Director


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