Maine Calling Podcast
Invasive Species: What Non-Native Species Are The Most Problematic in Maine & What Can Be Done?
Lake Stewards of Maine Invasive Species Program Director, Roberta Hill, called in to alert listeners to the threat of aquatic invaders at minute 37:50.

Variable Milfoil

Variable leaf milfoil (myriophyllum heterophyllum) is already present in 27 Maine lakes systems, including streams.

Do you know your Milfoil?

loads of milfoil

Eurasian Milfoil

Eurasian milfoil (myriophyllum spicatum), the more aggressive colonizer of the two, has been found in several Maine water bodies.

BLIMP Science Committee

Invasive watermilfoils

Watermilfoils are rooted, submerged aquatic plants found naturally in lakes and streams. Two non-native watermilfoils threaten the quality of Maine/NH fresh waters; Variable leaf milfoil (myriophyllum heterophyllum) and Eurasian watermilfoil (myriophyllum spicatum), the more aggressive colonizer of the two, has been found in several Maine water bodies.

Native watermilfoils

Maine/NH are home to six native water-milfoil species. Five of these are leafy milfoils, bearing some resemblance to one or more of the invasive milfoils, Alternate-flowered water-milfoil (Myriophyllum alterniflorum), Farwell’s water-milfoil (Myriophyllum farwellii), Low water-milfoil (Myriophyllum humile), • Northern water-milfoil (Myriophyllum sibiricum), Whorled water-milfoil (Myriophyllum verticillatum).

The sixth native species, dwarf water-milfoil (Myriophyllum tenellum), is a diminutive bottom dweller. Lacking true leaves, and not bearing any resemblance to the invasive milfoils.

History of Variable-leaf Milfoil in Balch Lake

Milfoil was found in Balch Lake in 1999. Variable-leaf milfoil generally occurs in waters up to eight feet deep; however, with Balch’s water clarity variable leaf milfoil has been found in waters as deep as 20 feet. Variable milfoil is an aggressive aquatic plant that can form dense mats that congest waterways and crowd out native aquatic plants. Thick growth of this plant can impair recreational uses of waterways including boating, swimming and fishing. Dense growth of variable-leaf milfoil degrades the native habitat of fish and other wildlife, and may also provide breeding areas for mosquitoes. The main method of dispersal of this plant appears to be fragmentation. Plant fragments are moved around by people, animals and water currents. If milfoil gets out of control, we will lose boating, swimming, and fishing along our shorelines; we will be cutting a path through the milfoil to get to deeper water.

Treatment of Variable Milfoil


Management methods currently include mechanical removal, benthic barriers, herbicides and lake drawdowns. At this time, there are no know biological controls for milfoil.


The first diver harvesting began in 2001. The DASH (Diver Assisted Suction Harvest) boat was introduced in 2011 with professional divers hired in 2012.
Currently the approach has mainly been the mechanical harvesting method. The DASH vessel and divers harvest mid-May through June and then again for a few weeks after Labor Day. Although harvesting can greatly reduce the Variable Milfoil biomass in a water body, harvesting also causes fragmentation, and fragments are capable of producing new plants. Some fragments may drift down stream or attach to boats and wildlife and create new infestations elsewhere.

Milfoil Dive Boat

Herbicide Treatments

Herbicide treatments of New Hampshire waters have occurred annually since 2002. The New Hampshire Department of Environmental Services authorizes the use for specific areas with an independent company, SOLitude Lake Management doing the actual application.

In 2019 a new herbicide, ProcellaCOR, will be used for the first time. ProcellaCOR was developed to specifically target variable leaf milfoil while minimizing the effect on other native plant species.

Educate yourself and others

Educate yourself and educate others. Tell your friends and neighbors about the threat, especially if they are a boater who might inadvertently spread the plant. Whenever you fish or boat, look for milfoil; early detection will help keep it from spreading. If you think you found milfoil, contact your association rep or BLIMP. Someone will take a sample, have it verified by the state, and then schedule treatment or pulling of the weed. BLIMP has used Maine’s office of Plant identification in Auburn and recommends we use state services to test for milfoil rather than private companies.

Clean your boat

Check your boat often and remove all plants. You may have picked up milfoil while boating on Balch, or from other lakes. DO NOT throw it in the lake, please dispose of it properly. Always remove all plants from your boat, trailer, fishing gear and anchor when going in and out of a body of water.

Getting ready to collect milfoil

Clean the Nets

Please check with your association President to see what week your association has net cleaning duties. You can always check with BLIMP to volunteer anytime you are available. Please see the volunteer page for more information. 

milfoil cleaning the net

Send a Donation

It costs BLIMP $35,000-40,000/year to control milfoil. Most members of Lake Associations make an annual donation to BLIMP. A number of associations include the donation as a line item on the annual association assessment. We suggest $50 per camp, but whatever you can afford is the right amount.
Send checks to:
PO Box 0494
East Wakefield, NH 03830
Your money will help pay for divers, DASH vessel operations and any herbicide treatments. The property owners on Balch Lake must join in to keep milfoil under control. Milfoil will not go away.

The towns of Acton, Newfield and Wakefield all put money in their annual town budgets to help BLIMP keep on top of the milfoil issue.

Milfoil effects on other lakes

During the summer our divers are at Lake Arrowhead attacking milfoil there. In 2016 a home was listed for sale on Lake Arrowhead. It was built in 1994, 7 rooms, 3 bedroom, 2 full baths, on 1.49 acres with 855 feet of water frontage. It was being sold furnished with many other amenities. The asking price? $259,000. Do you think milfoil may have something to do with the price? 

May 2019 Central Maine (Portland Press) – No boats are allowed in parts of Annabessacook Lake in Monmouth and Great Pond — including Great Meadow Stream — in Rome, at least for the time being. The Maine departments of Environmental Protection and Inland Fisheries and Wildlife have issued a temporary ban on watercrafts in portions of those bodies of water to suppress the growth of variable-leaf milfoil. “The purpose of the restrictions is to reduce fragmentation by closing it off to boats,” said Maine DEP.

This is why it is so important to keep milfoil controlled in Balch Lake.