posted Nov 1, 2018, 5:22 PM by Lake Iroquois Association   [ updated Nov 1, 2018, 5:23 PM ]

Press Release: October 19, 2018

Contacts: Chris Conant, President, Lake Iroquois Association 802-316-6714

Jamie Carroll, Secretary, Lake Iroquois Association 802-989-9439


Recently the Lake Iroquois Association (LIA) was notified of the denial of a permit application to treat Lake Iroquois with herbicide Sonar to significantly reduce the prevalence of the invasive species Eurasian Water Milfoil (EWM). LIA partnered with the town of Williston on this application. The Vermont Department of Environmental Conservation (VT DEC) considered this permit application for nearly two-years. This was proposed to prevent further native species loss and reduce the impact on recreational uses of the lake. In 2014 LIA contracted with Northeast Aquatics to conduct an aquatic plant survey prior to the permit application. That survey found that 70.7 acres of the lake was infested by Eurasian Water Milfoil.  This is 67% of the lake’s littoral zone (area of a lake in which aquatic plants grow) and suggested that an additional 33 acres of milfoil colonization is possible.  EWM has become the dominant aquatic plant in the lake. Another survey in 2017 found similar results. Since applying for the Sonar treatment LIA has conducted Diver Assisted Suction Harvesting (DASH) and installed Benthic Barriers in the lake to control the EWM in the most heavily infested areas of the lake.

Following nearly a decade of work to limit nutrient flows into the lake by stream remediation projects, implementing a greeter program at the state fishing access to prevent further invasives from entering the lake, instituting many educational programs including publication of a lakeshore property owners manual, and working with property owners to create shoreline riparian buffers, LIA embarked on the EWM control program at the request of lake users. The plant survey was commissioned in 2014 and in 2015/2016 LIA met several times with VT DEC staff, as well with local town Selectboards and Conservations Commissions, representatives from other lake associations, and Lake Iroquois property owners and users to discuss control options. This culminated in applications for a DASH permit in early 2016 and the application for the Sonar permit in November 2016. Sonar has been used safely in Vermont lakes since 2000 to control EWM and has been widely used in other states to control this invasive species, including in drinking water reservoirs.  The proposed treatment concentrations were well below EPA guidelines for drinking water.  

The Lake Iroquois Association has worked tirelessly in this effort over many years to research best practices for controlling EWM. The application for the Sonar permit included a 5-year plan for management which included continued use of both DASH and Benthic mats (bottom barriers) which already were in use at the lake.  Diverse funding sources, state grants, municipal contributions, and private funds help ensure the continued success of the efforts.  The goal of the use of  Sonar was not eradication but was intended to reduce the EWM enough to allow the other control methods to be effective and sustainable.

LIA has used Benthic barriers in a channel near the state fishing access to limit the spread of this invasive species. The use of Benthic Barriers is not benign because they kill all plants under them and affect fish spawning.  Therefore they can only be used in a very limited area, for example, to keep a boat channel open, but are not a solution for control of EWM in a wider area of any lake.  In 2016 and 2018 LIA hired AB Aquatics to conduct Diver-Assisted Suction Harvesting (DASH) of milfoil on Lake Iroquois. DASH can cause fragmentation, harvest non-target species, and disrupt the lake bottom. Again, this is a method that is part of an integrated EWM management plan but also is slow, and as noted can be disruptive to native species, as well as being very expensive.  The LIA plan was and continues to be a control program that combines these various methods, including the judicious use of herbicide at lowest effective concentrations, in such a way that this invasive is reduced and controlled so that native species can repopulate and flourish thereby enhancing the biodiversity and health of the lake ecosystem.

At the same time, the LIA continues its many other activities aimed at enhancing and maintaining the health of Lake Iroquois and its surrounding ecosystem.  These include our greeter program in which boats entering and leaving the lake are checked for invasives and cleaned at our boat wash station. Other efforts are our several stream remediation projects to reduce runoff along the west shore,  which are showing a significant reduction of nutrients and sediment entering the lake; ongoing efforts to inform and support lakeshore property owners and lake users in best management practices; help with creation of no-mow zones and riparian buffers to prevent nutrient runoff into the lake; continued monitoring and regular sampling and data collection to support evidence-based water quality activities. All of these many successful projects, the ongoing education and outreach efforts, and the 40+ years of water quality data collection have been done by dedicated volunteers, volunteers who continue to commit to the hard work of protecting and enhancing the water quality and health of Lake Iroquois and sharing their knowledge and experiences with other lake associations in the state in order to collectively protect the health of Vermont’s valuable water resources.

LIA remains committed to a program to control EWM to ensure the rich native aquatic plant community in the lake and, to eliminate the monoculture caused by the EWM infestation, so that appropriate recreational uses of the lake can continue and the health of the lake is protected. The association will continue to research ways to control EWM, to consult with other lake associations, lake users and property owners, municipalities, and the state to develop best practices and to work with all stakeholders to enhance the health of the Lake Iroquois ecosystem. 

The initial application (2240-ANC), denial, and replies to public comments are available from this web directory: 

For more information, go to our Facebook page:, check out our website: or email us at

Lake Iroquois Association,
Nov 1, 2018, 5:22 PM