milfoil treatments

Eurasian Water Milfoil is an invasive plant that has taken over parts of the lake in depths from about 3 feet to about 18 feet. The plant has been a problem in Lake Wononscopomuc since at least 1975. In 1988 the lake association with generous help from The Hotchkiss School bought a marine harvester and donated it to the town of Salisbury. Each year since the Town, Hotchkiss and the association have spent up to $30,000 per year to trim the milfoil during the growing season. The plant can crowd out native plants depriving the lake of the diversity is needs to survive in a healthy state and support its normal aquatic live population.

The milfoil has been mapped in 1989, 1999 and again in 2004. There has been some change in the amount of milfoil over the years. The experience of other lakes across the country has been that milfoil coverage may be reduced for several years, but that it always returns unless treatments are applied to restrict its growth.

The association engaged Dr. George Knocklein to do an extensive survey during the summer of 2007 to update the location of the Eurasian water milfoil and identify and locate other plants in the lake. The location of other plants is particularly important for the planned treatment of the milfoil.

There are 2 weeds on the Connecticut Bio-Diversity Databank list of threatened or endangered species. Any milfoil treatment would have to be structured, implemented and then monitored to avoid damaging those weeds.

There are a number of possible milfoil treatments. Harvesting is currently employed on Lake Wonscopomuc. Most other methods have proven impractical or have shown little success.

Hand pulling is difficult in depths up to 18 feet over a wide area. The lake is drawn down in autumn to reduce shore line erosion, but the lake is too deep (106 feet) to expose most milfoil to a killing freeze.

Weevils have not worked so far and require a suspension of harvesting. Suction harvesting in conjunction with divers using a hand pulling technique is very labor intensive and expensive. Hydro-Raking has been used by individual property owners with some success. It can cost$150 per hour and the property owner then has to dispose of the mass of silt and weeds that are raked up from the lake bed. In addition the milfoil usually reasserts itself within a few weeks and then grows as much as an inch per day.

The lake association then turned again to Aquatic Control Technology, Inc. for a recommendation on treatment in our lake. The company has successfully treated the milfoil in Twin lakes for the past four years. A.C.T. recommended treatment with two herbicides. They are outlined in the reports that follow. However, after a public forum was held on January 19, 2008, it was apparent there was insufficient public support to proceed with a herbicide treatment. The board of directors voted to instead increase harvesting for the next summer and study whether mechanical means would be sufficient to control the milfoil.

Report On Board Meeting December 1, 2007

Column for Lakeville Journal December 6, 2007

When ever there is a proposal to do something differently there are always going to be questions raised. When the members of the Lake Wononscopomuc Association voted to pursue an herbicide treatment program they realized that questions about their plans would have to be answered and they would have to provide a forum for everyone to present their views. The board of directors met December first and voted to create a committee on public education. The first decision was to schedule three public forums for members of the public to present their views to the association. The first forum will be held January 19th at 2:00PM at Town Hall.

In advance of that meeting the association will present information on specific issues each week in a column such as this one. The purpose of both the columns and the forums is to assure that everyone has all the data, scientific research and plans necessary for a rational discussion when the time comes for the Board of Selectmen to make a decision on town participation.

In addition all the plans, research reports and data we gather will be forwarded to the First Selectman’s office to be available for public reference. Of course, all information will be available at the lake website There you will also find links to independent and university research reports.

The association is proceeding slowly and carefully with a milfoil treatment program. The first step the board of directors took was to order a vegetation study in 2004 to update previous reports on the lake environment. In 2006 we commissioned a study by Dr. Nina Caraco of the Institute for Ecosystems Studies to update her 1990 and 1992 reports on the nutrient composition of the lake or its trophic state. Then this past summer we engaged Dr. George Knoecklein to do an extensive vegetation survey. He took samples from 260 locations around the lake to identify accurately every type of plant growing in the water. It is important to know not just where the milfoil is but what the distribution is of all other plants.

The association board of directors then decided at its meeting December 1, 2007, to seek a treatment of 4.3 acres in the middle of the lake with a product called Reward and another 4.6 acres on the western side with a product called Renovate OTF. We would continue harvesting the milfoil in most of the rest of this 353 acre lake and we would continue to provide the benthic barriers that keep the Town Grove swimming area free of milfoil.

In future columns we will deal specifically with the issues of health and safety, effectiveness, impact on the fish population, nutrient loading, results in other Connecticut lakes and the studies and surveys we will commission each year as we go forward to preserve, protect and improve the lake environment.

Column for Lakeville Journal, December 13, 2007

What Are The Alternatives?

It is understandable after the Lake Wononscopomuc Association proposed using an herbicide to control the Eurasian water milfoil people would ask if there aren’t alternatives that might be more natural. From all the reports and recommendations we have read and commissioned it is clear the preferred course of action is an integrated aquatic plant management program, which is the path the Association has voted to follow.

Before you can develop a management plan you have to determine what the problem is and how it affects a particular lake. Wononscopomuc was the site of heavy industry in the 18th century with its iron ore foundry, then dairy farming and later tourism. A steam railroad ran along its western shore bringing thousands of people to fairs and picnic outings. Now it is surrounded by residential development and used for swimming, fishing and boating. Despite almost 300 years of recorded human use the lake is still in pretty good shape. It is classified as mesotrophic by limnologists. Our goal is to preserve and improve it.

The milfoil causes a number of problems. First it is an invasive species. It has been shown in thousands of lakes across North America to crowd out native weeds and reduce the bio-diversity of the ecosystem. It is a major detriment to swimming and boating. But it is extremely important that the solution to the milfoil problem not create other problems.

The integrated management approach includes actions in the watershed to reduce the flow of nutrients into the lake, to maintain as much natural environment as possible and to guard against the invasion of other species such as zebra mussels. It calls for a combination of physical, mechanical and chemical treatments to remove nuisance aquatic plants. That is why we will continue to provide the barrier mats at The Town Grove to keep the swimming area milfoil free. We will continue harvesting the milfoil in most areas. Homeowners can continue hydro-raking. We will only treat two small areas with herbicides. Then more studies will be done to assess their impact and effectiveness. The treatment will be done by professional lake management specialists in late spring when the milfoil is just starting to grow. That will eliminate the risk of a large bio-mass sinking in the lake.

The lake environment is a delicate eco-system and the integrated approach allows us to reduce the milfoil gradually over several years while continuing to remove some of the nutrient laden biomass, preserving threatened or endangered plant species, allowing native species to grow back and maintaining oxygen levels to support the fish population. You will find more information about the lake at

 How Do We Know These Herbicides Are Safe?

Every herbicide must be registered by the United States Environmental Protection Agency for use in the United States. Before an aquatic herbicide is labeled by the EPA the Federal Insecticide, Fungicide, and Rodenticide Act of 1974 requires research that may involve 10 years of work and up to 140 different kinds of tests and analyses to complete.

Because of advances in scientific knowledge herbicides that were first registered before 1978 must be reregistered to ensure they meet today’s more stringent standards. Data required for aquatic herbicide registration includes, but is not limited to the following:

  1. Potential residue in water
  2. The environmental fate of the compound or where it goes after application and what happens to it when it gets there
  3. How the compound breaks down and what the breakdown products are
  4. Whether the compound is absorbed through the skin by test animals
  5. Short term or acute toxicity of the compound to test animals
  6. Whether the compound causes birth defects, tumors or other abnormalities after long term exposure
  7. Toxicity of the compound to aquatic organisms such as waterfowl, fish and invertebrates


Aquatic herbicides must have the capacity to be taken up by plants quickly in sufficient amounts from water to be toxic to the target plants and pose no more than a one in a million chance of causing significant damage to human health, the environment or wildlife resources. Some states have set even stricter standards.

The two herbicides chosen to reduce the Eurasian water milfoil in Lakeville Lake, Reward (Diquat) and Renovate (Triclopyr) have met these requirements and are approved for aquatic use. There is more than sufficient data to confirm their safety over the long term.

The EPA Consumer Fact Sheet reports Diquat has been used extensively in the United States since the late 1950s to control both crop and aquatic weeds. It is a contact herbicide and is injected under water to control milfoil by disrupting photosynthesis. It is very water soluble so does not accumulate in fish or animals and quickly dissipates from water by binding strongly to soil and sediment particles. That makes it unavailable for uptake by aquatic organisms. Its half life in the water column is less than 48 hours according to The Extension Toxicology Network of Cornell University, Oregon State University, the University of Idaho, the University of California at Davis and Michigan State University.

Triclopyr is a newer herbicide, but it has under gone testing since 1984. It is injected into the water column at very low concentrations. It is selective to milfoil and other broadleaf plants leaving many of the native aquatic plants unaffected. Like diquat it is very water soluble, does not accumulate in fish or animals and is rapidly degraded by sunlight and microbial action. The Washington State Department of Health contracted for an independent study of Renovate in 2003 – 2004 and concluded that the diluted levels of Triclopyr allowed for use in lakes are safe for humans, fish, waterfowl and the environment.

The purpose of these articles and the public forums this winter is to provide information and resources so that everyone can base their decisions on fact not fear. We hope that presenting sound scientific evidence will alleviate any concerns.

Mary Silks

The Lake Wononscopomuc Association


Column for Lakeville Journal, December 20, 2007

Column for Lakeville Journal, January 3, 2008

The Facts About Reward

Reward (Diquat dibromide) is one of the aquatic herbicides proposed to treat the invasive Eurasian water-milfoilin Lake Wononscopomuc. Diquat dibromide is a contact herbicide generally used as a pre-harvest desiccant for various seed crops such as wheat and oats as well as for the control of aquatic weeds.Its largest use is as desiccant on potato crops.It has been used for agricultural purposes since the 1950’s and over 250,000 lbs. are used on crops every year in this country. Diquat applied to aquatic systems as a weed control agent disappears from the water rapidly through adsorption to plants and sediments and by dilution in a large body of water.

There have been some concerns about any possible health effects from treating the milfoil with Reward. There are no reports in the scientific or medical literature listing any adverse effects to the nervous, endocrine and reproductive systems. It is not considered carcinogenic or mutagenic. There are findings of cataract formation in laboratory animals. These studies involve feeding large amounts of pure chemical to mice, rats and dogs every day over long periods of time, months and years. These amounts of herbicide are hundreds and even thousands of times the levels used in aquatic environments. There have been no cases of human cataract formation associated with the use of Diquat in agricultural or aquatic applications.

The Washington State Department of Ecology contracted with an independent company to prepare a document concerning potential human health effects and environmental impact from aquatic applications of the herbicide diquat. This information was published in 2002 in a 411 page report and reflects the most recent information concerning the toxicology of diquat and potential health risks to the public associated with diquat aquatic weed control. They reviewed over 100 published studies that included children and adults and various routes of exposure.Based on this review they found that even persons swimming in water treated with the highest use-rate allowed (0.37 ppm) would not be expected to experience significant adverse health effects. This report and other articles on herbicides can be found as links in our website

Aquatic Control Technology , the company applying the herbicide, safely treats about 350 ponds and lakes a year throughout the northeast and has had success in treating milfoil at lower than allowed concentrations.They have proposed treating about 5 acres of our 353 acre lake with between 1 and 1.5 gallons of Reward per acre (0.18 ppm), well below the allowed 0.37 ppm. This will disappear rapidly through adsorption to plants and sediments and by dilution into the over 4 billion gallons of water in the lake. At East Twin Lake they applied Reward at 0.18 ppm.When tested 24 hours after the application , the level was only 0.02 ppm.This is the tolerance level set for Diquat in drinking water. At 5 days after treatment the level in the water at East Twin Lake was only .0045 ppm. Aquatic herbicides have been shown to be an effective and safe component of an integrated lake management plan and would help us meet our goal of preserving and improving Lake Wononscopomuc.

Column for Lakeville Journal, January 10, 2008

The Facts About Renovate

Renovate is the trade name for the herbicide Triclopyr, a selective contact herbicide that is specific for broadleaf plants.(Dicots) Along with Diquat (Reward) it has been recommended as a treatment for the invasiveEurasian Water-milfoil in Lake Wononscopomuc.It works by disrupting a plant hormone that controls the growth of the plant. Eurasian Water-milfoil is a dicot. It is very sensitive to low concentrations of Renovate. Since most of the native aquatic plants are monocots they are not affected by the herbicide. It rapidly enters through a plant’s leaves and stem , then moves down into the roots, disrupting the plant’s metabolism.

Because Renovate affects processes that occur in plants and not in humans or other animals this herbicide is very safe for humans when used properly . This is the conclusion of an independent companycontracted by the Washington State Department of Ecology to conduct a search of the scientific and medical literature,review published studies , toxicology information and present a risk assessment of exposure to this herbicide. This 360 page study can be reviewed by a link in our website, The study also addresses the environmental effects this herbicide may have. It does not persist in the environment.It is rapidly absorbed by plants. It is diluted by the large amount of water in a lake and it is degraded rapidly by sunlight. (Photolysis)

There has been concern about the product label for Triclopyr. Its label reads – Danger: Corrosive. Causes Irreversible Eye Damage. Harmful if Swallowed or Inhaled. Prolonged or Frequently Repeated Skin Contact with Herbicide Concentrate May Cause an Allergic Skin Reaction in Some Individuals. Eye damage has been shown in animal studies and would also occur in humans if concentrated chemical were to come into contact with the eye. These studies also showed that a 1:3 dilution showed only moderate effects and a 1:7 dilution showed no effect. When used in aquatic applications it is used at a 100,000 times dilution and it is in the water at a concentration of not greater than 2.5 parts per million.This stresses the importance of proper application rates, timing and application techniques in handling these products. That is why we have enlisted the help of Aquatic Control Technology in the milfoil treatment. They have safely treated4 lakes in Vermont for 2 years with Renovate at 2 ppm . Testing 48 hours after treatment showed only 0.2 ppm present. This is well below the allowed level in drinking water set by the EPA of 0.4 ppm.

There are many other states that have also conducted studies on aquatic herbicides, Wisconsin, Minnesota, New Hampshire and Florida all have information on the internet. One excellent source is the Purdue University online slide presentation titled “Why Aquatic Herbicides Affect Aquatic Plants and Not You.” There is also a link on our website to the Purdue presentation.

Our first public forum will be held at 2:00PM Saturday, January 19th at the Town Hall. We will offer additional information on our lake treatment plan and hope to answer questions and address any concerns people may have.

Mary Silks

The Lake Wononscopomuc Association

Column For Lakeville Journal, January 17, 2008

The Lake Wononscopomuc Forum

During the last two months the Lake Wononscopomuc Association has presented the facts about our lake management plan. The plan includes benthic barriers at the Town Grove, continued weed harvesting on much of the lake, hydro-raking by homeowners, paying for a boat watch to keep zebra mussels out of the lake, drawdown of the lake in winter to reduce shoreline erosion, reminders to lake front property owners to have septic tanks pumped, education about the danger of phosphate based fertilizers and consideration of zoning changes to protect the lake environment from over development.

Because none of the actions taken so far have reduced the impact of the invasive plant known as Eurasian water milfoil we are also planning to treat two small areas with aquatic herbicides. Less than 2.5% of the lake would be affected. The association has ordered a number of expensive studies and surveys in preparation for this plan. We have not asked town taxpayers to fund it. The town has spent more than $200,000 harvesting the milfoil so far on a treatment that continues year after year.

Any environmentalist knows that an invasive species by definition is dangerous. The Eurasian milfoil crowds out native plants and may threaten marine life. And we have a valuable recreation fishing asset to protect. Last spring the D.E.P. stocked our lake with 7,500 brook, brown and rainbow trout. When we considered using an herbicide we had to be sure it was not only effective and safe for humans, animals and water fowl, but that it had also been proven safe for our fish population.

We turned to Aquatic Control Technology of Sutton, Massachusetts, for recommendations. This company has 31 years experience, treats over 150 ponds and lakes in Connecticut with herbicides each year and has been contracted by the Connecticut DEP for the last 5 years for “On-Call” Invasive Aquatic Plant Management Services. There has not been one report of injury to swimmers at any of the lakes they treat. Among the lakes they treat in Connecticut are Twin Lakes, Bantam Lake, Indian Lake in Sharon, and Woodridge Lake in Goshen and Highland Lake in Winchester.

They recommended two products which we asked them to test the first year on two small areas of less than 5 acres each. The products are Renovate OTF and Reward. They are designed to attack the milfoil type of plant specifically. We chose one area in the middle of the lake because it is far from the Town Grove and can be tested to be sure this product will not harm any plants the DEP lists as threatened or endangered. The other test area is on the northwestern side. It is also far from the Grove and has dense beds of milfoil.

Reward has been used for many years. Renovate is a newer product, but it was used without problems by Aquatic Control Technology last year in Taunton Lake in Newtown, Connecticut, and Renovate OTF was applied in three Vermont public lakes last year. They reported that most if not all of the flakes dissolved within hours of application and 48 hours later concentrations in the treatment area were down to 0.1 – 0.2 ppm. The Massachusetts Department of Agricultural Resources studied the toxicity of Renovate’s main ingredient, Triclopyr, from laboratory and field investigations and approved its use in 2004 if the label restrictions are followed strictly.

If the EPA thought there was a risk to children’s eyes or if the Connecticut DEP had heard of any injuries caused by these products, does anyone think people like Chuck Lee, Peter Aarrestad, Nancy Murray or Bob Orciari would allow them to be used without even requiring a swimming restriction on the label?

We know some people still have concerns and that is why we scheduled our first forum for Saturday, January 19th, 2:00PM at Town Hall. We want to hear your questions. If we don’t have the answers, we want the opportunity to get them. You can find more information and links to detailed reports on milfoil treatments and products at our website


Bill Littauer, President

Lake Wononscopomuc Association