Invasive Species

What is an invasive species?

An invasive species is a type of plant or animal that is not native to a particular ecosystem, whose introduction does or is likely to cause economic or environmental harm or harm to human health

What types of invasive species exist in our watershed?

The Wentworth Watershed Association divides the invasive species in the watershed into two categories: Aquatic and Land.

What Are Aquatic Invasive Species?

Aquatic Invasive Species or Aquatic Hitchhikers are species of plants and animals not native to our watershed. You can read more about these species on the New Hampshire Department of Environmental Services website. Luckily, in our watershed, we have a dedicated group of volunteers who act as citizen scientists, helping the Wentworth Watershed Association to identify and respond to the invasive species as they apear. Below you can see photos snapped by Colin Ross, a member of our Dive Team.

The introduction of non-indigenous invasive aquatic plant species to New Hampshire’s waterbodies has been on the rise. These invasive aquatic plants are responsible for habitat disruption, loss of native plant and animal communities, reduced property values, impaired fishing and degraded recreational experiences, and high control costs. Once established, invasive species are difficult and costly to remove.

This is a small patch of milfoil and if allowed to grow, it comes to the surface and clogs the waterway. Milfoil can grow at a rate of 1 inch per day, and propagates by root, fragmentation and seed. It naturally fragments when the waters get colder. It can grow to around 15ft long.

Variable milfoil (Myriophyllum heterophyllum) arrived in Lake Winnipesaukee in 1979 and found its way to Mast Landing at Crescent Lake the following year. A Weed Watch Committee was formed in 1983 in response to this unwanted aquatic invader. The State of New Hampshire helped the Town of Wolfeboro and Lake Wentworth Association (now the Wentworth Watershed Association) pay for placement of chemically treated mats in an attempt to eliminate the milfoil. In 1991 1995, 1999, and 2003, large areas of Crescent Lake were treated with Diquat, a contact herbicide. In 1991, milfoil was discovered between Allen Albee Beach and Hersey Brook in Lake Wentworth. Mats were laid out immediately, which seemed to stem the spread of milfoil.

NHDES introduced new treatment procedures in 1994 to include chemical treatments, manual weed pulling, chemical mats, and plant surveys. A NHDES plant survey in 2006 found milfoil common in Heath Brook, Hersey Brook, and Willey Brook tributary coves in Lake Wentworth. Over the years the weed watchers and volunteer dive team have located and targeted several areas in Crescent Lake and Lake Wentworth. These localized infestations have been managed by volunteer divers who hand pull, DASH Boats, chemical treatment with 2, 4 D, a systemic herbicide, and a foliar chemical treatment in 2020 of Goodwin’s Basin with ProcelaCOR.

The Wentworth Watershed Association, with grant support from the NH Lakes, coordinates volunteer and paid Lake Hosts at the Mast Landing boat launch to provide voluntary boat and trailer inspections and to inform the public about invasive species. Continuing to monitor and control variable milfoil and other invasive species will help preserve the water quality of Lake Wentworth, Crescent Lake and Sargent’s Pond for the future.

Weed watchers patrol the lakes and ponds in areas they recreate throughout the summer and report sightings to the program coordinator who send out the dive team to verify and schedule treatment. The dive team typically hand pulls milfoil every Saturday through out the summer. Watch the video below, made by dive volunteer Colin Ross, that shows the dive team and surface support team at work.

To learn more about the aquatic invasive species in NH waterbodies watch this identification training link from aquatic plant expert from DES- Amy Smagula.

Photos courtesy Colin Ross who is one of the divers on the Dive Team.

What are Land Invasive Species?

An invasive plant is one that is not native to a particular ecosystem, whose introduction does or is likely to cause economic or environmental harm or harm to human health. It is capable of moving aggressively into an area, monopolizing light, nutrients, water, and space to the detriment of native species. The UNH Extension Program has publicly available information on land invasive species and protocols in dealing with them. Below are some additional resources provided by state and local agencies.

What can I do to prevent the spread of Invasive Species?

The first step is awareness and education about the problem. Utilize the Wentworth Watershed Association resources to learn more about invasive species in your area, and contact the Wentworth Watershed Association has multiple ways to get involved.

Learn how to get involved

No matter your time commitment or education level, there’s a way that you can help the Wentworth Watershed Association combated invasive species.

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