What is exotic milfoil?

In New Hampshire the most problematic milfoil species is known as variable milfoil (myriophyllum heterophyllum). This plant has infested close to 50 waterbodies in New Hampshire. This species is not native to the waters of New Hampshire and therefore our ecosystem is not adapted to its presence. When it enters a waterbody it quickly reproduces replacing native vegetation. This vegetative replacement alters the ecosystem negatively affecting water quality and threatening ecosystem biodiversity.

What does variable milfoil look like?

Variable milfoil is a submerged aquatic plant characterized by feathery leaflets surrounding a thick, reddish main stem. The plant flowers between July and August via a stalk that emerges above the water surface and contains small green leaves. Milfoil prefers to grow in relatively calm and shallow (less than 20 feet) waters with a muddy bottom. Fragments that break off the plant and grow roots are the primary form of reproduction and spreading. Wind, current, boats and waterfowl transport these fragments. Milfoil is a hearty plant that grows up to one inch per day and even continues growing beneath the ice during winter. Unfortunately, identification of exotic (variable) milfoil versus the 5 native, noninvasive species can be difficult and must be performed by an aquatic biologist. Flowering specimens are optimal for identification.

How and when did it get in the Squam Lakes?

No one knows exactly how it got here or when it arrived. In mid-July 2000, the NHDES confirmed the presence of variable milfoil in the Squam River below the dam in Ashland. In early August, the NHDES surveyed Little Squam Lake and identified a dense infestation in the cove occupied by Kimbell Marina and under the boathouses in the channel next to the Route 113 Public Boat Ramp.

What can be done to get rid of the milfoil?

At present there is no method to completely remove or eradicate non-native variable milfoil from a waterbody. Unlike Eurasian milfoil that is a problem in any waterbody it enters in the United States, variable milfoil is actually native and adaptive to the southern United States. Invasive infestations of variable milfoil are only problematic in four northern states where it has been introduced. The current focus in New Hampshire is to encourage eradication research and to implement management techniques to minimize or control the infestation.

What are some of the management methods?

Physical and/or mechanical harvesting techniques have had limited success since they further fragment milfoil resulting in increased reproduction. Drawdown of a waterbody with the intent of freezing the milfoil is not typically successful in New Hampshire due to the insulating effects of the snowcover we receive. In some cases drawdown coupled with a freezing of the waterbody and rapid water level increase can be used to physically de-root the plants, however this is difficult to implement on large waterbodies. Herbicide application in some cases represents the most effective method of management. In limited infestation areas bottom barriers have been used to cover the plants. Handpicking of plants is also an effective method to remove limited growth.

We recognize that variable milfoil degrades fresh water ecosystems drastically and thus believe an aggressive management program is necessary. Again, eradication is not an option, but control is. By law, any education and management program must be under NHDES supervision. Since the discovery of milfoil in the summer of 2000, the SLA has been working with the NHDES to come up with management alternatives for the infestation of the Squam Lakes. An ad hoc milfoil task force has been formed with SLA staff and members, the marina operators, and the SLA's consulting ecologist. Thus far, we are working on several approaches, but we need more support in all of these approaches:

1. Education:

We have posted signs at all launching facilities identifying the presence of invasive milfoil to raise public awareness to minimize spreading. We also staff the public boat ramp on Route 113 and distribute literature to boaters on invasive plants. Our staff removes plant fragments from boats and trailers both launching and pulling to help minimize the spreading.

2. Prevention of fragment spread:

SLA has distributed hand nets to the marinas and is encouraging removal and desiccation (sun drying) of fragments on a daily basis. Thousands and thousands of fragments (probably hundreds of thousands) can be seen on still, hot days in the channel opening to Little Squam.

With NH-DES approval, SLA placed a second surface net at the Kimbell Marina cove entrance, creating a buffer zone to decrease the release of fragments from the cove. These require frequent milfoil removal and volunteers are needed to perform this task.

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3. Identification of infested sites:

SLA has organized volunteers through the NHDES Weed Watcher program. These volunteers are trained to recognize different aquatic plants, and they survey areas of the lakes. Milfoil fragments identified are removed, and the volunteers are encouraged to pull rooted variable milfoil plants. Questionable specimens are sent to SLA for identification, and all other specimens are desiccated or placed in household trash. NHDES is notified of new infestation sites.

4. Prevention of growth of rooted plants:

Hand pulling has been carried out by SLA and NHDES in the channel, Little Squam, and at Squam Boat Livery. SLA is pursuing further bottom barrier possibilities and future herbicide application, and discussions continue regarding other management options.

5. Legislative Efforts:

In cooperation with the New Hampshire Lakes Association, the SLA has been working this legislative session on HB592 that would increase milfoil funding. Currently the state funds exotic aquatic plant programs by allocating $1.50 from every boat registration fee which equates to $150,000 annually. The lake associations in New Hampshire believe this program needs to be funded on the order of $1,000,000 annually to be effective and that more of these funds need to be directed toward research. HB592 passed a full House vote and is currently in the House Ways and Means Committee for consideration of the funding mechanism.

Chris Devine and Maggie Mumford install barrier bottom material in Squam.

What can I do to help with the milfoil infestation?

• Volunteer to be a Weed Watcher - call SLA (603) 968-7336. Volunteers are needed on Big and Little Squam Lakes.
• Familiarize yourself with what invasive milfoil looks like.
• If you see any fragments on the water surface, collect them, or, if you see plants rooting, pull them.
• Notify SLA of any suspected new infestation sites. Bring a specimen to SLA by wrapping it in a wet paper towel, placing in a labeled Ziploc bag.
• Frequently inspect your boat by tipping up your engine or outdrive and remove any fragments. Please inspect after passing through an area with infestation, such as the channel. Don't prop wash fragments off you'll create many new plants!
• Dispose of any fragments or plants in your household trash.

Where is exotic milfoil likely to spread?

Variable milfoil fragments tend to establish new plants in water depths of less than 15 feet and in muddy or disturbed areas, such as dredged coves. Possible infestation areas are shown in light green on the milfoil map. Please sign up as a Weed Watcher if you live or vacation near any of these areas.