Eurasian Watermilfoil Treatment in Lake Fairlee
Eurasian Watermilfoil is the common name for myriophyllum spicatum, a floating aquatic plant native to Europe, Asia, and northern Africa. It was imported and sold in the United States as a decorative aquarium plant. It is a problem in many northern lakes and has been in Lake Fairlee for about two decades. By outgrowing many native lake plants it now dominates the native flora in many parts of our lake.
Because it roots in the lake bottom and reaches for the sunlight at the surface, it grows primarily in water less than 15 feet deep. Although it can propagate via flowers and seeds, in our lake it propagates mostly via vegetative propagation. Even small fragments can take root. Thus, it spreads easily within a waterbody and from lake to lake, fragments traveling on boat bottoms and trailers. (This is one of the many things our Greeters watch for.) In the spring it is frail and brittle and easily fragmented. In the summer it grows strong and thick. As it grows, it uses up natural nutrients in the lake to the exclusion of other native plants. It also crowds out sunlight falling on native vegetation.
Lakes with increased nutrient pollution are more susceptible to invasive plants such as these. We do not know if the currently raising phosphate levels in Lake Fairlee contribute to our milfoil problem. If allowed to spread unchecked it threatens to clog the lake with dense mats of plant material; parts of the lake would become inhospitable to boaters and swimmers, and ultimately property values and tax revenues could suffer. This has happened to other lakes. We are working to prevent this.
At this time there is no known way of completely eliminating milfoil from our lakes. There are no natural predators. Statewide and locally, several means of control have been tried. Importing insect predators could be an option, but as of now, no insect has been found hearty enough to keep up with the rapid milfoil growth. In Lake Fairlee, we have used plastic lake floor barriers but found them to be logistically difficult and ecologically unnatural. Cutting and collecting the vegetation by underwater divers worked somewhat but was expensive and never totally effective. After trying many control techniques, we realized the best option is to treat the lake with an herbicide.
What is the risk of using an herbicide? Treating an invasive weed like milfoil requires similar decisions that one makes when treating an illness. What benefits do we expect and do these outweigh the potential harms or side effects of the treatment? This is usually not a simple calculation. We have learned that complete eradication of Eurasian milfoil is a very remote possibility without removing all living organisms from the lake and starting all over. Over the recent years, we have successfully kept this invasive weed under control with an application every two to three years of an herbicide (trade name Renovate) at the smallest effective dose possible. (The amount of herbicide used is becoming smaller with improved science.)
Under licensed supervision by the Vermont State Department of Environmental Protection, Division of Lakes and Ponds, a well-established and experienced company helps us evaluate the Lake Fairlee needs year-by-year. The evaluation process takes place in September. Application of the herbicide takes place the following June just as the milfoil is waking up and is most susceptible to the herbicide action. Of note, the state of Vermont has changed the allowed treatment protocols. Going forward, we anticipate treating smaller areas of the lake on an annual or semi-annual basis, rather than the every three years or so frequency of the past over larger areas.
A new herbicide has become available which is expected to be a better option for our lake. This herbicide, florpyrauxifen-benzyl, trade name, ProcellaCOR is in a class of plant pharmaceuticals that mimic the plant hormone, auxin. Auxin is essential to the growth of higher plants, much like human growth hormone. ProcellaCOR works not as a poison to kill the plant but has a copy of the auxin-like hormone to completely alter the plant metabolism. Under the stimulation caused by ProcellaCOR, the plant outgrows its food supply and dies of starvation.
In our lake, flowering plants are in two classes: “monocots” and “dicots" that differ only somewhat in how they look, but more significantly in their embryology (early growth) and metabolism. They react differently biochemically with the herbicide ProcellaCOR. Remarkably, the toxic hormonal action occurs only in dicots (for a description of the characteristics and differences of monocots and dicots see biologyeducare.com/monocotyledon-and-dicotyledon/). As a dicot, milfoil is very susceptible to ProcellaCOR. Fortunately, most of the aquatic plants of Lake Fairlee are monocots and do not respond to ProcellaCOR's hormonal action. We have watched the effect of the earlier used herbicide (Renovate) with the same auxin-mimic action over the last three applications, approximately 10 years. The other dicots in the lake (water lilies, bladderwort) have been only minimally impacted by the herbicide treatments and have not died, while the Eurasian milfoil has outgrown its food supply, dies of starvation, turns black, and sinks to the bottom.
What about safety? The chemical florpyrauxifen-benzyl (ProcellaCOR) is approved by the FDA and the State of Vermont as long as it is used in clearly specified ways. What about plants, animals, and the ecosystem as a whole? Two extensive reports, one from Massachusetts and one from Washington State provide more information on this topic. It is a matter of judgment whether the details of research into several species can be extrapolated to our own Lake Fairlee. An ongoing inventory of the Lake Fairlee Watershed species and focus on a the local “web of life” will give us tools to monitor changes. (see the Nature part of this LFA website and the Lake Fairlee Watershed observations on the iNaturalist website.) We are not treating the Eurasian milfoil solely for human convenience, but also to bring a better natural balance to our lake.
We cannot reverse the “footprints” of man – but we will watch where we step.
Because it roots in the lake bottom and reaches for the sunlight at the surface, it grows primarily in water less than 15 feet deep. Although it can propagate via flowers and seeds, in our lake it propagates mostly via vegetative propagation. Even small fragments can take root. Thus, it spreads easily within a waterbody and from lake to lake, fragments traveling on boat bottoms and trailers. (This is one of the many things our Greeters watch for.) In the spring it is frail and brittle and easily fragmented. In the summer it grows strong and thick. As it grows, it uses up natural nutrients in the lake to the exclusion of other native plants. It also crowds out sunlight falling on native vegetation.
Lakes with increased nutrient pollution are more susceptible to invasive plants such as these. We do not know if the currently raising phosphate levels in Lake Fairlee contribute to our milfoil problem. If allowed to spread unchecked it threatens to clog the lake with dense mats of plant material; parts of the lake would become inhospitable to boaters and swimmers, and ultimately property values and tax revenues could suffer. This has happened to other lakes. We are working to prevent this.
At this time there is no known way of completely eliminating milfoil from our lakes. There are no natural predators. Statewide and locally, several means of control have been tried. Importing insect predators could be an option, but as of now, no insect has been found hearty enough to keep up with the rapid milfoil growth. In Lake Fairlee, we have used plastic lake floor barriers but found them to be logistically difficult and ecologically unnatural. Cutting and collecting the vegetation by underwater divers worked somewhat but was expensive and never totally effective. After trying many control techniques, we realized the best option is to treat the lake with an herbicide.
What is the risk of using an herbicide? Treating an invasive weed like milfoil requires similar decisions that one makes when treating an illness. What benefits do we expect and do these outweigh the potential harms or side effects of the treatment? This is usually not a simple calculation. We have learned that complete eradication of Eurasian milfoil is a very remote possibility without removing all living organisms from the lake and starting all over. Over the recent years, we have successfully kept this invasive weed under control with an application every two to three years of an herbicide (trade name Renovate) at the smallest effective dose possible. (The amount of herbicide used is becoming smaller with improved science.)
Under licensed supervision by the Vermont State Department of Environmental Protection, Division of Lakes and Ponds, a well-established and experienced company helps us evaluate the Lake Fairlee needs year-by-year. The evaluation process takes place in September. Application of the herbicide takes place the following June just as the milfoil is waking up and is most susceptible to the herbicide action. Of note, the state of Vermont has changed the allowed treatment protocols. Going forward, we anticipate treating smaller areas of the lake on an annual or semi-annual basis, rather than the every three years or so frequency of the past over larger areas.
A new herbicide has become available which is expected to be a better option for our lake. This herbicide, florpyrauxifen-benzyl, trade name, ProcellaCOR is in a class of plant pharmaceuticals that mimic the plant hormone, auxin. Auxin is essential to the growth of higher plants, much like human growth hormone. ProcellaCOR works not as a poison to kill the plant but has a copy of the auxin-like hormone to completely alter the plant metabolism. Under the stimulation caused by ProcellaCOR, the plant outgrows its food supply and dies of starvation.
In our lake, flowering plants are in two classes: “monocots” and “dicots" that differ only somewhat in how they look, but more significantly in their embryology (early growth) and metabolism. They react differently biochemically with the herbicide ProcellaCOR. Remarkably, the toxic hormonal action occurs only in dicots (for a description of the characteristics and differences of monocots and dicots see biologyeducare.com/monocotyledon-and-dicotyledon/). As a dicot, milfoil is very susceptible to ProcellaCOR. Fortunately, most of the aquatic plants of Lake Fairlee are monocots and do not respond to ProcellaCOR's hormonal action. We have watched the effect of the earlier used herbicide (Renovate) with the same auxin-mimic action over the last three applications, approximately 10 years. The other dicots in the lake (water lilies, bladderwort) have been only minimally impacted by the herbicide treatments and have not died, while the Eurasian milfoil has outgrown its food supply, dies of starvation, turns black, and sinks to the bottom.
What about safety? The chemical florpyrauxifen-benzyl (ProcellaCOR) is approved by the FDA and the State of Vermont as long as it is used in clearly specified ways. What about plants, animals, and the ecosystem as a whole? Two extensive reports, one from Massachusetts and one from Washington State provide more information on this topic. It is a matter of judgment whether the details of research into several species can be extrapolated to our own Lake Fairlee. An ongoing inventory of the Lake Fairlee Watershed species and focus on a the local “web of life” will give us tools to monitor changes. (see the Nature part of this LFA website and the Lake Fairlee Watershed observations on the iNaturalist website.) We are not treating the Eurasian milfoil solely for human convenience, but also to bring a better natural balance to our lake.
We cannot reverse the “footprints” of man – but we will watch where we step.