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What's Going on with the Invasive Milfoil in Great Pond?

Updated: Aug 27, 2020

No new infestations, but plenty of work to do!

Invasive variable milfoil (Myriophyllum heterophyllum) was identified in Great Pond in 2009. While no new infestations have been found since 2016, the fight against invasive aquatic plants remains as urgent as ever. Maine lakes are particularly vulnerable to invasive species due to warming temperatures, proximity to infrastructure, and the movement of people around water bodies. Adapting management methods to the changing environment is essential in removing existing infestations and preventing new ones.

Invasive plants like variable milfoil are well adapted to living in a wide range of environmental conditions and geographical areas, making it easy for them to take over native plants and reduce biodiversity very quickly. Due to its rapid growth rate of up to an inch a day, variable milfoil wreaks havoc on native ecosystems, blocking native plants from the sun, increasing debris on the lake bottom, decreasing oxygen levels, and creating “dead zones” where aquatic organisms cannot survive. The plants also provide breeding grounds for mosquitoes, inhibit recreational activities, and lower property values.


Recap of 2019 

While early identification and prevention are our best tools against invasive aquatic plants like variable milfoil, removing existing infestations is critical to containing the spread and restoring ecosystem health. In 2019, we removed 28,480 gallons of invasive milfoil in Great Meadow Stream. We also worked in Belgrade Stream in collaboration with New England Milfoil and Friends of Messalonskee to keep variable milfoil from hopping over the dam. Using data collected from swimming the entire shoreline of Great Pond in 2018, we created priority maps to reduce future survey time, and developed a new way of mapping the infestation in Great Meadow Stream with maps based on plant dominance in order to facilitate comparisons and see trends to better predict growth in the future.

In 2019, we also received notice of milfoils popping up in many places around the lakes that we were able to verify as native milfoils and not new invasive infestations. This is good news because it means that native populations are filling up niches and forming better barriers against invasives!

So Far in 2020 

Early ice-out means early plant growth, so we started work early this year. We are working on the same three infestations in Great Pond: Great Meadow Stream, Rome Trout Brook, and Rome Meadow Stream. All three locations have been actively managed since 2012. In addition to hand-pulling and Diver Assisted Suction Harvesting (DASH), we use benthic barriers made of burlap to cover the plants and block them from sunlight. By using benthic barriers on invasive milfoil monoculture when the plants are still small, we are able to cover an area that would take over a week to clear manually in one day, leaving more time to spend on mixed areas. So far this year, we have removed 14,370 gallons of invasive milfoil and laid about an acre of burlap.

Biodegradable benthic barriers = environmentally friendly and saves on labor costs

Get Involved 

Early identification is the best tool against the spread of invasive plants. Survey your own shoreline for invasive plants and tell us what you find--we will train you! We are also always looking for volunteer Fragment Patrollers to paddle around and collect plant fragments, an essential part of the remediation process. Get in touch with Sharon Mann, 7 Lakes Milfoil Remediation Manager, and she’ll get you settled.


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