Archive for the ‘Herbicide’ Category

Herbicide Treatment Details for 2018

Tuesday, May 29th, 2018

The Lake Fairlee Association has received approval from the State to apply triclopyr to the lake to help control the growth of Eurasian milfoil.  The treatment will take place on Monday, June 11, beginning at 9:00 am.  It will require the effective closure of the lake to all activities for two days, and certain restrictions for several weeks.  See the Notice to Abutting Landowners below.

This years treatment is pursuant to and governed by a permit issued by the State Department of Environmental Conservation in 2015, which you can read about HERE.


(Click on image above for full size version)

2015 Year End Milfoil Report Now Available

Friday, July 8th, 2016

Better late than never?

The Lake Fairlee Association holds a permit from the State of Vermont that governs all phases of our milfoil control activities – including hand pulling, suction harvesting, bottom barriers, herbicide treatment, and our greeter/prevention program.  This permit requires that we conduct annual surveys of plant life in the lake, and that we file a report with the state annually.

Since 2010 we have contracted with (licensed) companies to conduct our various milfoil control activities, and they have been primarily responsible for filing these annual reports. The 2015 report was not completed and filed until July this year.  Nonetheless it contains lots of detail about Lake Fairlee’s milfoil program.  We provide it here for your information.

Click on image to download report (.pdf)

Click on image to download report (.pdf)

Where We Treated in 2015, and Why

Friday, June 19th, 2015

Chemical control of Eurasian milfoil is strictly regulated by the State.  According to the conditions of our permit we are allowed to apply triclopyr only to those “portions of the lake where EWM is too abundant (moderate to dense) to be cost-effectively managed using non-chemical techniques and is highly susceptible to fragmentation and continued spread.”  The state determines those locations based on the required quantitative aquatic plant survey from the previous fall.  Here are the results of that survey.  Red dots indicate dense milfoil, yellow is moderate, green is sparse, and empty circles indicate no milfoil found at that location.

2014 fall survey map

Click on map for larger image

These surveys are designed to take statistically accurate samples.  They do not report every instance of observed milfoil.  Rather they collect plant samples from a predetermined grid of locations and observe all the species present.  This allows the State (and us) to measure long term changes on all plant populations in the lake, to preclude unanticipated effects of the herbicide use.

Here are the results of the pre-treatment survey done this May.  For this survey every instance of observed milfoil was recorded.  Again, red circles are dense patches, etc.  This map also shows the areas approved for herbicide application.  For the most part they coincide with many of the densest growths of milfoil.

spring survey

Click on map for larger image

The herbicide was applied in the indicated areas on Tuesday, June 16th.  Note that not every location where there is milfoil was treated.  To those (including the author) whose littoral zone contains milfoil but was not treated, we offer apologies and hope that you understand the constraints under which these treatments are done.  We understand that there are divers who are experienced with Eurasian milfoil removal who can be hired to clear it from your shoreline.

More about the Herbicide Application

Thursday, June 18th, 2015

renovate otfThe herbicide is delivered in 40 pound bags that look like they might contain fertilizer.  Although we are only putting a very little bit of chemical in the water, we want it to be absorbed at or near the roots of the plants so far as possible.  So the chemical comes blended in pellets of chunks of clay, which will sink to the bottom before dissolving and releasing their active ingredient.

P1050350_SnapseedIt is poured into hoppers on the back of the boat.  Under each of these there is a powered spinning disk that spreads the pellets several yards either side of the boat.  (click on the thumbnail to enlarge)  The driver follows a programmed course that zigs and zags back and forth to cover the designated treatment area.  And the speed of the boat and the hoppers’ flow rates are regulated to ensure that the herbicide is delivered at the desired concentration.

Milfoil Density Map for Herbicide Treatment

Tuesday, May 19th, 2015
click above for larger

click above for larger

The conditions of our State issued Aquatic Nuisance Control Permit only allows us to apply the herbicide where the milfoil growth is moderate or dense.  The attached map reflects data collected last September, but conditions probably have not changed significantly since then.  Another survey has been completed in the past week.  Those results will govern the treatment locations on June 16th.  We will share them here when we can.

Herbicide Treatment Scheduled for Tuesday, June 16th

Tuesday, May 19th, 2015

Due to the harsh winter and late ice-out in the northeast, the plant growth in the lakes behind previous years. As we know, the Milfoil must be growing for the herbicide treatment to be effective. We had previously had a soft treatment date of June 8, 2015 however that is now not an option. Our treatment contractor is moving the treatment date back a week to 6/16/15 in order to have the best efficacy as possible. The more growth of the Milfoil, the more effective the treatment. The lake will be surveyed in the coming days to confirm.

We apologize for any inconvenience this may cause however it is in all of our best interest for the treatment not to fail.

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As with previous treatments, the lake will be closed to all uses for the day of the treatment and the day following.  On Thursday June 18th recreational use may resume.  This includes swimming, boating, fishing, etc.  We recommend not using lake water to irrigate your lawn for several weeks, however.  The herbicide (triclopyr) is a plant hormone which is very safe for us (humans, pets, etc) but toxic to certain kinds of plants.

Details of our Herbicide Treatment Permit

Tuesday, May 19th, 2015

The State of Vermont is very strict about the release of chemicals in the environment.  Our use of triclopyr is subject to a long list of conditions and restrictions that are enumerated in the permit issued to us earlier this week.  The application process is exhaustive, and approvals have to be obtained from the Department of Health and the Department of Fish and Wildlife before the final permit is issued by the Lakes & Ponds Management and Protection Program of the Department of Environmental Conservation.  Yes, we get to learn quite a bit about navigating the State’s bureaucracy along the way.

permit final

Click on image above to view document


How Safe is Triclopyr?

Monday, May 18th, 2015

We have made the decision to again treat Lake Fairlee with the herbicide triclopyr (Renovate™).  Based on our experience with this chemical in 2010 and 2013 we believe this to be a safe and effective way to deal with the growth of Eurasian milfoil in our lake. At that time we did as much research as we could to reassure ourselves that what we were doing would not have any harmful effects.  You can see what we found then on the page called Herbicide Resources.

Can the chemical get into my well water?

Property owners who have wells near the lake, particularly shallow wells, have experssed concern for the safety of their drinking water supply.  The State of Washington’s Department of Health has looked at this question, and found:

“The limited mobility of triclopyr in soil, low absorption constant, and high rate of microbial and photolytic degradation in water and sediment would indicate that this compound would have little potential for the extensive mobility required to contaminate groundwater supplies.”

They go on to note that:

“This assumption is supported by data collected by the US Geological Survey (USGS), as this federal agency has collected over 850 groundwater samples over a five-year period in the Pacific Northwest area and these samples have been examined for pesticide residues. Triclopyr has never been detected in any of the groundwater samples taken by the USGS, despite extensive use as an herbicide in this region in forestry applications over a 20-year timeframe.”

We only know of one published instance of well water being tested for triclopyr after an adjacent lake was treated.  In this case the level detected was 0.0 ppb after two weeks.

 How do we know it is safe?

Triclopyr is a manmade chemical that does not occur naturally.  Although it has been used for more than three decades without any recorded incidents, how can we know that it never will?  It is hard to prove a negative.

Knowledge is power, and in this case we believe that understanding more about what triclopyr is and how it works can inform our belief in its safety for this use.

Auxins are a class of plant growth hormones.  They are involved in the regulation of the growth of plant cells.  They are directly responsible for phototropism, the tendency for a plant to grow towards the sun.  A simplified version of the way this works is that within a given cell the auxins are inhibited by sunlight, so the growth occurs more at the end of each cell that is not exposed to sunlight, and the whole plant appears to reach towards the sunlight.

A little about auxins

Chemical formula for triclopyr

Triclopyr is a synthetic chemical called an auxin. Auxins are a class of chemicals found in plants that help regulate their growth. For example, phototropism is caused by inhibition of auxins by sunlight, so that the shaded underside of the plant grows more than the sunny part, causing the plant to ‘grow toward the sun.’  Abnormal amounts of these auxins can disrupt the normal growth of a plant, even kill it, so auxins are also used as herbicides.  Also, different species of plants respond differently to auxins, making them useful for weed control. Finally, triclopyr is an effective herbicide for dicots(flowering plants and trees) but not for monocots (grasses and conifers).  More information HERE.



No Herbicide Treatment in Summer of 2014

Thursday, May 1st, 2014

The Lake Fairlee Association has had variable success dealing with the invasive Eurasian milfoil that has invaded our lake and many others around the region.  We do other things as well – we promote safe boating practices and encourage shoreline planting that is best for the health of our lake.  And we continue to build community and provide social opportunities around the lake — as we did 20 and 40 and 60 years ago, long before the advent of the milfoil.

In 2010 we successfully treated all of the affected areas of the lake with the herbicide triclopyr.  Within weeks 99% of the milfoil was rotting on the bottom of the lake.  Unfortunately the herbicide only kills the milfoil that extends into the water column; the extensive root system persists.  Also the small fraction that survived can reproduce by seeding, propagation, or fragmentation.  And new milfoil can be introduced by transient boaters or even waterfowl.

Management of milfoil is heavily regulated by the State.  That is not a complaint, as we are in favor of strict controls of what goes in the lake, particularly of herbicides.  But it means that politics and bureaucracy are involved at every turn in our attempts to control the weed.  Milfoil again affects significant portions of the lake, but we will not be treating it with herbicide this year.  We will negotiate with the State and attempt to duplicate our 2010 success in 2015.

Extent of Milfoil Growth at the end of 2013

Tuesday, February 25th, 2014

This is what was on our minds as we approached the 2014 season.September 2013 Survey

September Survey Map