The Harrisons Bay Association (and other bays on Lake Minnetonka) employs several herbicides to manage aquatic vegetation in our lake. It’s crucial to understand the potential health and environmental risks associated with these chemicals. Below is an overview of the primary herbicides in use.
🧪 What Happens When Weeds Are Chemically Killed:
Aquatic plants (including weeds) store nutrients like phosphorus and nitrogen in their tissues as they grow. When you kill them with herbicides (like Diquat, Fluridone, or ProcellaCOR), they rapidly decompose in place. During decomposition, those stored nutrients are released back into the water column — especially phosphorus. This can lead to algae blooms, including toxic blue-green algae, which feed off the phosphorus. This leads to worsen water clarity and green water.
Diquat
here is a great read on Diquat: https://www.counterpunch.org/2025/09/01/america-is-still-using-diquat-a-toxic-weedkiller-banned-in-much-of-the-world/
Health Risks
- Diquat dibromide is highly persistent, with reported field half-lives of greater than 1000 days and 160 days in lake sediments due to it’s low bioavailability. [Source]
- Human Exposure: Diquat is a highly caustic substance that can cause severe mucosal injury to the mouth, esophagus, stomach, and small intestine. Acute exposure may lead to nausea, vomiting, diarrhea, severe dehydration, and disruption of fluid and electrolyte balance. In severe cases, it can result in multi-organ failure, including effects on the kidneys, liver, heart, lungs, and central nervous system. [Source, Source]
- Neurological Effects: Exposure has been linked to nervousness, irritability, aggression, disorientation, and, in severe cases, coma and seizures. [Source]
Environmental Impact
- Aquatic Life: Walleye and Perch are especially sensitive to diquat, displaying toxic symptoms when exposed at label application rates. In a study of early life stages of fish, 8–10-day-old walleye showed an LC50 of 0.75 mg/L, indicating a high level of sensitivity. [Source, Source]
Fluridone Herbicide
Environmental Impact
- Aquatic Life: Slight to moderate toxicity to freshwater fish and invertebrates [Source]
- PFAS Classification: The active ingredient, florpyrauxifen-benzyl, is classified as a PFAS (“forever chemical”) due to its persistence in the environment.
- Non-Target Plant Damage:
- It can kill or suppress native aquatic plants along with invasives. These native plants are vital habitat for fish spawning and protection. Loss of vegetation can lead to reduced biodiversity and destabilized ecosystems.
- Indirect Effects on Fish:
- Killing too much vegetation (including coontail and pondweed, which are habitat for walleye and panfish) reduces oxygen in the water when the plants decompose. This can stress or kill fish, especially in smaller or shallow bays.
🌿 Ecosystem Concerns
- Algae Blooms:
When plants die off from Fluridone treatment, they release phosphorus into the water. That phosphorus can fuel harmful algal blooms, which further reduce oxygen levels and hurt water quality. - Persistence:
Fluridone breaks down slowly in water. Depending on light, temperature, and sediment, residues can linger for weeks to months. - Food Chain Impact:
Fewer aquatic plants → fewer invertebrates → fewer fish → fewer loons, eagles, and other wildlife that depend on fish.
ProcellaCOR
Health and Environmental Concerns
- PFAS Classification: The active ingredient, florpyrauxifen-benzyl, is classified as a PFAS (“forever chemical”) due to its persistence in the environment. [Source] [Source]
- PFAS Definition from the State of Minnesota: “Perfluoroalkyl and polyfluoroalkyl substances” or “PFAS” means a class of fluorinated organic chemicals containing at least one fully fluorinated carbon atom. [Source]
- Regulatory Actions: Calls for a pause on ProcellaCOR’s use have emerged due to concerns over its safety. [Source, Source]
- Community Concerns: Residents in Lake George have voiced opposition to its use over environmental and health concerns. [Source]
Potential Risks and Concerns
- Non-Target Plant Damage: Studies show ProcellaCOR may harm native aquatic vegetation such as coontail, waterlilies, and watershield—not just invasive species. [Source]
- PFAS Concerns: The active ingredient, florpyrauxifen-benzyl, has been flagged by the Minnesota Department of Agriculture as a potential PFAS compound—a class of “forever chemicals” linked to long-term environmental persistence and possible health effects. [Source] [Source]
- Ecological Disruption: Critics argue ProcellaCOR may unintentionally impact aquatic ecosystems, affecting the food chain and biodiversity. [Source]
- Herbicide Resistance: There is a potential for weed populations to develop resistance to ProcellaCOR, especially if used repeatedly in the same area. This resistance could reduce the herbicide’s effectiveness over time.[Source]
Auxin-Mimicking Herbicides
Health and Environmental Concerns
- Non-Target Plant Damage: Despite their selectivity, auxin-mimicking herbicides can negatively affect native plant species, reducing seedling emergence and biomass. [Source]
- Herbicide Resistance: Repeated use can lead to herbicide-resistant weeds due to mechanisms like enhanced metabolic detoxification. [Source]
- Environmental Persistence: Some auxin mimics, such as aminocyclopyrachlor, persist in soil and can damage sensitive crops even seasons after application. [Source]
- Ecological Disruption: Sub-lethal exposure may alter plant-herbivore interactions, affecting feeding patterns and ecosystem balance. [Source]
Conclusion
While managing aquatic vegetation is vital, balancing these efforts with the potential risks of chemical treatments is crucial. Understanding the health and environmental impacts of herbicides like diquat, fluridone, ProcellaCOR, and auxin-mimicking herbicides will help the community make informed decisions to protect both our waters and our well being. We don’t believe that that Harrison Bay Association understands that these chemicals are really bad for our lake