Overview
Unfortunately, the management of invasive weeds have become part of “Lake Life” in NH and in the states surrounding us. The spread of invasive weeds can easily happen when:
- humans move their boats between water bodies without following “Clean, Drain, Dry”
CLEAN off any plants, animals and algae found during your inspection and dispose of it away from a waterbody, and use any cleaning technologies at launch sites before entering, and after leaving a waterbody.
DRAIN your boat, bait buckets, bilges and other equipment away from the waterbody, leaving your boat’s drain in the open position during transport.
DRY anything that comes into contact with the water
- animals and waterfowl either consume or visit infestation areas and then visit other regions of the same lake to other nearby lakes
Currently, Big Island Pond has three main invasive weeds: european naiad, variable milfoil and fanwort. Mitigation techniques for controlling invasive weeds vary by state and type of invasive weed.
NH DES typically recommends a combination of the following for the biggest impact on controlling invasive weeds:
- benthic barriers – elimination of sunlight to plant life by covering area with a barrier
- diver assisted suction harvesting (DASH) – diver essentially uses a water vacuum to collect and move invasive plants and roots to a nearby boat where debris is bagged and later disposed of in a landfill or compost pile
- herbicide application – typically applied during plant’s growth cycle to kill the target plant (actual herbicide varies depending on the plant)
European Naiad (also known as Spiny Naiad)
In the fall of 2019, European Naiad was spotted in the Blueberry circle cove of Big Island Pond. NH DES was contacted and confirmed the presence of this annual invasive weed, just prior to drawdown. AB Aquatics was deployed to DASH the plants. Due to the fragile nature of the plant, DASH activities were immediately halted. Based on the experience of other NH lakes, DES recommended monitoring the cove, as this annual plant rarely came back. European Naiad is known under many names: Najas minor, brittle waternymph, Spiny Naiad and Brittle Naiad to name a few.
In mid-July 2020, Blueberry circle residents confirmed European Naiad was back. In mid-August, 11 benthic barriers were deployed in the cove. Feedback from AB Aquatics and residents suggest that the benthic barriers were not enough to address this issue. NH DES provided guidance and what raw materials they had to deploy fragmentation barriers and Restricted Access buoys for this area. Through the work of BIP volunteers those materials were deployed and more were built and deployed around Turtle Island, a small island across from Blueberry circle cove.
We continue to work with NH DES to understand this new invasive weed. While many NH lakes have experienced this annual invasive weed only one other NH lake has seen a recurrence like BIP has. Northeast Pond found this weed in 2005 with a 41 acre infestation. Three years later, they had decreased the footprint by 50% by using a herbicide and DASH activities.
European Naiad threatens boating, swimming, fishing, and property values for all of us if the spread is not addressed. To learn more about this invasive weed check out some of these sources: Maine Lake Volunteer Monitoring Program , NOAA GLANSIS and Illnois Wildflowers site.
Variable Milfoil
In 2000, variable milfoil was spotted in Big Island Pond. This perennial weed, grows uncontrolled in the Northeast states due to ph levels and with sunlight can grow 3+ inches per day. Big Island Pond has been long been battling this infestation utilizing significant investment with the help of countless volunteer hours, Friends of Big Island Pond and AB Aquatics. Looking at snapshot of the last 12 years in our battle against variable milfoil has resulted in:
- $400,000 dollars spent harvesting around 25,000 gallons of variable milfoil in about 500 DASH days
- the creation of Friends of Big Island Pond, a 501©(3) organization, created by BIP residents. Friends of Big Island Pond was created to established as a funding mechanism to protect the watershed of Big Island Pond.
The deployment of benthic barriers and DASH activities have been successfully used on Big Island Pond forcing back variable milfoil from a large infestation to where we are today – maintenance. Regular DASH activities and our annual drawdown help to control the spread of this highly aggressive invasive weed.
Fanwort
Fanwort has been part of Big Island Pond since the 1950s. While fanwort is considered an invasive weed, NH DES considers fanwort a fundamental part of the BIP ecosystem. Luckily this invasive weed does not spread or infiltrate other areas of the lake. Our annual drawdown helps control this invasive weed.
Long Term Management Plan
The purposes of this exotic aquatic plant management and control plan are:
1. To identify and describe the historic and current exotic aquatic infestation(s) in the waterbody;
2. To identify short-term and long-term exotic aquatic plant control goals;
3. To minimize any adverse effects of exotic aquatic plant management strategies on non-target species;
4. To recommend exotic plant control actions that meet the goals outlined in this plan; and
5. To evaluate control practices used in this waterbody over time to determine if they are meeting the goals outlined in this plan.
This plan also summarizes the current physical, biological, ecological, and chemical components of the subject waterbody as they may relate to both the exotic plant infestation and recommended control actions, and the potential social, recreational and ecological impacts of the exotic plant infestation.
The intent of this plan is to establish an adaptive management strategy for the long-term control of the target species in the subject waterbody, using an integrated plant management approach.
Prepared by:
NH Department of Environmental Services
March 2022