Main content

Milfoil Control Efforts

Eurasian Watermilfoil (EWM) was first identified near the public fishing access in Lake Iroquois around 1990.  Various efforts were made to control the infestation including hand pulling, use of weevils, and establishment of the LIA Greeter Program.   However, by 2014, it was clear that the EWM infestation was spreading out of control, seriously impeding boating, swimming, fishing, and causing an alarming decline in native aquatic species.  In order to understand what was happening and what our options were, the LIA Board began to study and research options for reducing and controlling EWM.

The result of this work has been the development of a long-range management plan that involves a multi-faceted approach.  This plan includes a careful and judicious use of the herbicide, ProcellaCOR, in a small area at the northern end of the lake where the infestation is most dense.  This approach is balanced by historic and continued use of other methods such as diver-assisted suction harvesting (DASH), use of benthic (bottom) barriers in certain limited areas, hand pulling, and ongoing work to continue to reduce nutrient levels in the lake.  These efforts serve as an integrated approach that when combined with LIA’s Greeter and Boat Wash Program, aim to prevent further introduction of invasives into the lake and to control and reduce the EWM invasive that is already there. 

The plan proposes to treat up to 40% of the littoral zone (‘near shore’ areas where these aquatic plants grow) with ProcellaCOR.  This is slightly less than 16% of the entire lake.  The concentration rate to be used will be no more than 3 PDUs (Prescription Dose Units) which is equal to a rate of 1.93 ppb (parts per billion).  At this rate on this proportion of the lake it is expected that the concentration level in the entire lake would be no more than 0.47 ppb on the day of application.  For reference, imagine 1-2 drops in an Olympic-sized swimming pool. Invasive plant species are a real threat to ecosystems. 

ProcellaCOR was granted Reduced Risk Status by the US EPA in early 2016 because of its promising environmental and toxicological profiles.  This product has been widely analyzed by universities, federal and state governments, and health departments.  Findings show that professional application of ProcellaCOR in accordance with the label will not cause adverse effects on human health or the environment.  Studies also indicate that chronic exposure did not result in carcinogenicity, mutagenicity, nor genotoxicity effects.  In addition, ProcellaCOR breaks down quickly in the environment (hours to days).  It was used on four lakes in Vermont in the summer of 2019. The Vermont Department of Health has declared the proposed ProcellaCOR treatment as not likely to result in an increase in concern for public health. The detailed permit application, including supporting documentation and data, the draft permit, and other materials can be found below.  


Permit to Control Eurasian Watermilfoil Issued

The Lake Iroquois Association (LIA) and the Lake Iroquois Recreation District (LIRD) are pleased to announce that an Aquatic Nuisance Control permit for the use of the herbicide, ProcellaCOR, to control the infestation of invasive Eurasian Watermilfoil (EWM) in Lake Iroquois has been issued. After many years of research and planning, we now have tools that promise to allow us to really begin to control the EWM infestation in the lake. The use of herbicide is one part of a multi-pronged effort to reduce and control this invasive and to begin to restore a more natural aquatic plant habitat in our lake. Besides this permit, we have permits to do  Diver-Assisted Suction Harvesting (DASH) and to selectively place bottom barriers. These efforts along with our outstanding greeter and boat wash program, our robust education and outreach efforts to lakeshore property owners and lake users, the completion of several runoff prevention projects, and our work to reduce Beebe Lane erosion all combine to protect and enhance beautiful Lake Iroquois.   

We have begun coordinating dates and creating a timeline for these various activities. Barring any restrictions due to COVID, we expect to do one day of herbicide treatment in late June and several weeks of DASH in August. As things fall into place, we will share more details with you. In the meantime, you can find the full herbicide permit which includes all the conditions which must be met on our website at

If you have questions or comments, please send us an email: info@

Photo by Pogo Senior