Update on Spiny Niaid

2023 Updates

Big Island Pond herbicide treatment will occur on Friday Aug 4 by Solitude Lake Management using a fan boat. Our 2023 herbicide treatment area is just under 31 acres compared to the 80+ acres mentioned in the initial permit application. After multiple surveys by the state and BIP, we have the below treatment map.

As expected, treatment areas include our inlets, coves and the outlet of BIP. With the seemingly never-ending rain this summer, our native plant life has made it a challenge to differentiate the invasive spiny naiad from our multiple native naiads.

Please note: the most recent abutter notices show a slightly bigger footprint than what will be treated. Treatment areas were adjusted to mirror confirmed growth seen by NH DES survey work done in July.

Below you will find the temporary water use restrictions for anyone with intakes 200ft of a treatment area, drawing water for drinking or irrigation purposes and to all wells and points with 50 feet of the treated areas:

Restriction time post treatment 
6 hours No swimming within 200 ft of treated area within 200 ft of treated area
1 day No water for livestock/domestic animal consumption within 200 ft of treated area
3 days No water for drinking, irrigation or mixing sprays for turf or landscape ornamental plants
5 days No irrigation for food crops mixing sprays for agricultural or production ornamental plants

Spiny Naiad Information

Big Island Pond (BIP) has a new invasive weed called Spiny or Brittle Naiad. This plant in Big Island Pond regrows every year from seeds and flowers roughly in July, producing more seeds. These seeds spread in the water column and reseed in the lakebed. It falls apart and spreads like a dandelion when disturbed. Spiny Naiad seeds are extremely small which adds to the challenges of controlling the spread of this invasive weed.

Unlike other nearby lakes where a few Spiny Naiad plants appear and disappear, we are not as fortunate as it is rapidly flourishing in our lake. We are one of two lakes in the State of New Hampshire where Spiny Naiad is rapidly growing and must be managed. In 2019, AB Aquatics unsuccessfully attempted to remove the plants. Alternatively, last year AB Aquatics laid down some benthic barriers on the lakebed in a heavily infested area which proved ineffective as well. A 2020-year survey has already identified BIP with up to 50 acres of potential Spiny Naiad infestation. DASH (Diver Assisted Suction Harvesting) is only effective in removing individual Spiny Naiad plants or small areas of infestation. It takes five weeks of diving/DASH to remove ONE acre of Spiny Naiad, and the 2020 survey has identified up to 50 acres of potential infestation. Unfortunately, there is only one dive company that has the capability of diving/DASH for Spiny Naiad and they have chosen to not engage with BIP for 2021.

The purpose of this document is to provide an unbiased overview of the available weed management techniques available to BIP. The information was gathered and organized by a task force of volunteers that live on the lake and have expertise in their respective fields. The information was gathered from public domain sources and vetted against other sources (vendor information, peer reviewed reports, etc).

The team is comprised of the current head of the Weed Management Committee and the prior head of the Weed Management Committee, a doctorate in biochemistry that worked in pharmaceutical development for 40 years, a career long engineer, a PhD botanist in molecular biology who works with molecular genetics in plants, and a PhD plant physiologist who was the head of a university plant sciences department with strength in weed science.

Spiny Naiad  Management  – Pros/Cons 

Herbicide Comparison

Herbicide Labels & Fact Sheets

Questions for Weed Task Force

Frequently Asked Questions



Ecosystem – The community of living organisms in and surrounding or lake, living and nonliving components of the environment, composed of plants, animals and microorganisms. For the purposes of this effort, we also include humans, pets, and shoreline as part of the BIP ecosystem.

DASH – Diver Assisted Suction Harvesting – Is a method of harvesting underwater plants. Divers identify unwanted non-native or invasive plants that need to be removed, pull them out by the roots and feed them into a suction tube that transports the plants to aboat to be hauled away. The results are immediate, chemical-free, long-lasting with ongoing maintenance. BIPC has been using DASH harvesting for over a decade to manage milfoil.

Benthic Barriers – A benthic barrier is a piece of material (film, sheet, BIPC has used tarps) that lays on the Benthos layer of a waterbody (bottom layer of water and the uppermost layer of sediment) to keep sunlight from getting to the nutrient-rich soil on the bottom. Benthic Barriers are cost effective and functional for small treatment areas. The material is typically heavier than water which allows it to settle firmly on the lake’s bottom, but in most cases, additional weight is needed to keep the material in place. Gases of decomposition forming under the material can be a problem and must be maintained by divers “venting” the gas by slitting the material.

Dredging – Dredging is the act of removing silt and other material from the bottom of bodies of water. It does a fairly complete job of clearing an area of all but the substrate material (earth), it will also remove or at least disturb the entire ecosystem of silt, biomass, living organisms, etc.in the dredged area, impacting the ecosystem

Monitor and Observe – This is the act of monitoring the concerned areas without immediate action. Inspecting for plant growth from the surface or with divers in order to see how a plant grows, propagates, survives the seasons, and its impact on the overall ecosystem.

Herbicides – Aquatic Herbicides are formulated to control a wide variety of aquatic weeds and are approved for use within a waterbody by state and federal organizations. Aquatic herbicides come in liquid or granular form to control and, in some treatments, prevent weed growth. Herbicides come in various forms and brands and each has different active properties. Herbicides must be applied by vendors that the state of NH has permitted to do so. 

Bioaccumulation – The tendency for a chemical to remain in animal tissue and accumulate in top predators (bass, otters, snapping turtles, people).

The information contained in this document is provided for informational purposes only, and should not be construed as legal or technical advice on any subject matter. You should not act or refrain from acting on the basis of any content included in this
document without doing your own due diligence or seeking other professional advice.