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 identifies two types of invasive species: 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 Fish and Game 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 that can appear. 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 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. These infestations have been managed in recent years by chemical treatment with 2, 4 D, a systemic herbicide and hand-pulling by divers. The LWA has supported a Lake Host 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 and Crescent Lake for the future.

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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