This commentary is by Cynthia Moulton, Ph.D., a professor at Castleton University who has taught ecotoxicology and ecology for over 20 years. Before that, she worked at the U.S. Environmental Protection Agency in the Office of Pesticides.
The Lake Bomoseen Association has applied for an Aquatic Nuisance Control Permit to use ProcellaCOR EC to control Eurasian milfoil. I encourage every person interested in this issue to read the label of this product.
In reading the label, one could be overwhelmed with the amount of information found on it, but one thing stands out — it is called a selective herbicide. Most people might assume that means it selectively kills only targeted aquatic nusiance weeds. However, when the word “selective” appears on a pesticide label, it means that it kills in a specific, targeted way.
The active ingredient in ProcellaCOR EC, florpyrauxifen-benzyl, is a synthetic analogue of an auxin. Auxins are plant hormones that regulate growth and development in plants — too little auxin impedes growth and too much auxin causes damage to the cell walls and death.
Florpyrauxinfen-benzyl mimics a persistent presence of a plant’s natural auxin and this results in over-stimulation of auxin-related gene synthesis. ProcellaCOR EC has a broad herbicidal spectrum, which ranges from broadleaf weeds to grass to sedge weeds; therefore, death can occur in a wide variety of plants, usually in days to weeks after exposure.
Thus, ProcellaCOR EC is not selective in targeting only nuisance weeds but will indiscriminately harm all aquatic and emergent plants in Vermont lakes.
Many anglers report reduced numbers of fish in lakes treated with herbicides. This seems like a paradox because herbicides are supposed to kill plants not fish. Plus, ProcellaCOR is considered nontoxic to fish.
Yet, Vermonters who fish often have a keen interest in and knowledge of the ecology of lakes and ponds. It is detrimental to the integrity of ecosystems for biologists to ignore the insights and observations of the people most in tune with these environments.
Consider that many anglers possess sophisticated sonar technology, so if the fish were there, the anglers would at least be seeing them on their sonar (catching them is another matter). But the reports from anglers indicate that they are simply not seeing fish in the treated lakes.
This might seem mysterious — but in fact this is a predictable scenario. When you kill the plants in a lake, you might not kill the fish, but you’ve taken their habitat and their food.
Try to imagine this. On land, an herbicide that killed or defoliated every plant in a given area would be obvious. There would be no birds, no squirrels, no bugs — just dead, dying and decaying plants.
No one would tolerate this kind of devastation for weed control in town fields or state parks. A homeowner would never obliterate every plant, shrub, bush and tree in their yard to rid their lawn of dandelions.
Think what would happen if homeowners treated their own 1-acre lawn in this manner, but the impacts seeped into the lawns of their neighbors. The removal of primary producers (plants and other photosynthesizing organisms) in an ecosystem is a phenomenon known as a “bottom-up trophic cascade” in the ecological literature. There are numerous studies that support the concept, regardless of whether the removal was due to an herbicide, fire, an herbivore (like a locust), or drought. In plain language, Vermont lakes treated with herbicides have experienced catastrophic food-web collapse.
One can argue that the treatment area for Lake Bomoseen is “only 200 acres.” In fact, it is 200 acres that can be treated up to three times in a season, plus two additional 200-acre lake sections that would be treated over three years.
Keeping the product in the designated 200 acres is impossible — just put a tiny drop of food coloring in a jar to see how solutes move in water. Undoubtedly, considerably more than 200 acres will be impacted.
Much of the defined treatment area is prime habitat for many of the lake’s animal species. The weedy regions are where aquatic insects, macroinvertebrates, small or juvenile fish and worms live, and these are the main food sources for many of the game fish anglers seek out.
These shallow zones, rich with aquatic plants, are where frogs and turtles live and these areas also serve as nurseries for juvenile fish. Marshy areas with emergent weeds are important for birds like song sparrows, red-wing blackbirds, great blue herons and more. In other words, these are vibrant and important communities of interconnected non-target organisms.
Using ProcellaCOR EC poses unacceptable risk and adverse effects to the nontarget organisms in Lake Bomoseen. The significant ecological risks alone should be enough to legally negate the permit request.
However, too often the desires and conveniences of people outweigh ecological concerns. I would like to think that in Vermont, of all places, we are better than that. I implore the Lake Bomoseen Association to withdraw its request for an aquatic nuisance control permit.
I also strongly encourage the aquatic and fisheries biologists of the Vermont Department of Environmental Conservation to place a moratorium on aquatic nuisance control permits that allow herbicide treatments for aquatic plants (unless there is a public health risk), until a more ecosystem-wide approach to risk assessment is defined and available.
