How To Control Coontail
Updated: Aug 9
Hello fellow Pondologists, and welcome back to the third episode of “Pond Weed Problems”! In this series, we go over how to control aquatic weeds and pests to help you reclaim your water.
A weed is simply a plant growing where it is not wanted. Just like dealing with crabgrass in a Kentucky Bluegrass lawn, if you want to get rid of a weed in your pond, it is YOUR pond—don't let anyone tell you that you can't!
Your pond might look like a peaceful oasis from the surface, but underneath, a silent takeover could be happening. It’s called Coontail, and while it looks like a harmless underwater forest, it’s actually a "clogging" machine that can ruin your fishing, kill your fish's oxygen supply, and turn your swimming area into a tangled mess. But stop! Before you grab herbicide and start spraying, you need to know that if your water is too muddy or your pH is too high, you might just throw your money down the drain. Today, we are diving deep into the "Secret Weapon" techniques and specific "Killer Cocktails" you need to take your pond back.
Note: Always check with your local laws and regulations before using any recommended chemical or biological treatment options. The herbicide label is the law.
The Ecology of Nuisance Submerged Plants
Unlike floating duckweed, Coontail (Ceratophyllum demersum) is a fully submerged aquatic plant native to North America. In moderate amounts, it is incredibly beneficial, providing critical shelter and spawning areas for bluegill, perch, and bass, while supporting the insects those fish eat. However, it becomes a problem when it forms a dense monoculture.
Identifying the Right Plant: Coontail vs. Look-Alikes
Proper identification is your critical first step so you don't waste time and money treating the wrong weed. Coontail is a free-floating plant with no roots, featuring stiff, dark-green leaves arranged in whorls (clusters of 5-12) around a stem that can grow 11 to 15 feet long. Its key identifier is its forked or branched leaves that bunch at the tip, giving it a "raccoon tail" appearance.
Table 1: Identification Guide
Feature | Coontail (Native) | Eurasian Watermilfoil (Invasive) | Chara (Macroalgae) |
Plant Type | Submerged Plant | Submerged Plant | Macroalgae |
Roots | No roots (free-floating) | Rooted in sediment | Rhizoids (root-like) |
Leaf Structure | Forked / Branched | Feathery (10-21 leaflet pairs) | Bristly, stem-like branches |
Feel in Hand | Rough, spiny, stiff | Smooth, limp, collapses | Gritty, bristly |
Smell | No distinct smell | No distinct smell | Musky odor when crushed |
The True Driver: Nutrients
If Coontail is native and beneficial, why does it take over? The answer is excessive nutrients (mainly phosphorus). Runoff from fertilized lawns, crop fields, or golf courses fertilizes the water. Coontail is highly efficient at absorbing these nutrients directly from the water column, growing into problematic mats.
The Recreation and Respiration Problem
Coontail creates a severe "clogging" problem in the water column that frustrates fishing. But the hidden danger is ecological. When these dense stands inevitably die in late summer or fall, decomposing bacteria consume huge amounts of dissolved oxygen. This creates anoxia (low oxygen) which can stress or kill your fish. Chemical intervention is often warranted to manage this "biomass" before an oxygen crash occurs.
Pre-Treatment Assessment: Do Your Homework
Because Coontail is submerged, you are treating the volume of the water, not the surface.
Step 1: Calculate Pond Volume
● The Formula: Surface Acres X Average Depth (ft) = Acre-feet.
● Overdosing wastes money and kills fish; underdosing renders the treatment ineffective.
Step 2: "Right of Way" Water Testing
Before choosing a chemical, you must test your water to ensure the herbicide has the "right of way" to work:
● The Turbidity Test: If your water is cloudy or muddy, do not use Diquat, because suspended sediment binds to and deactivates the chemical.
● The pH Test: Flumioxazin degrades extremely rapidly if your pond's pH is consistently above 7.5.
● The Water Exchange Test: Fluridone requires a 30-to-90-day contact time; do not use it if your pond has constant inflow and outflow.
● The Alkalinity Test: If using a copper-based herbicide, ensure your Total Alkalinity is above 50 ppm to avoid toxicity to fish.
A Comparative Analysis of Coontail Control Methods and Herbicides
For effective Coontail control, your herbicide must be delivered into the water column. You have two main strategies:
1. Contact Herbicides (The "Sprinters")
These act fast to kill the plant tissue they physically touch, making them great for spot-treating swimming areas or boat ramps.
● Diquat (Reward®): Fast and excellent for control, with low fish toxicity at labeled rates. Rate: 2 gallons per acre in a 50-gallon tank, or 24 ounces in a 4-gallon backpack.
● Endothall (Aquathol®): Highly effective. You MUST use the Dipotassium Salt formulation (Aquathol®) because the Amine Salt formulation (Hydrothol®) is toxic to fish. Rate: 5 to 10 gallons per acre.
● Flumioxazin (Clipper®): Fast-acting broad-spectrum control. Rate: 12 ounces per acre (only in pH under 7.5).
● Copper Complex (Komeen): Excellent control, but can be toxic to sensitive fish like koi and trout. Rate: 5 gallons per acre.
The "Killer Cocktails" for Tough Infestations
● For Low pH (<7.5): Combine Diquat and Flumioxazin.
● For High pH (>7.5): Combine Diquat and Komeen.
2. Systemic Herbicides (The "Marathon Runners")
These are absorbed and translocated throughout the plant for a complete, long-lasting kill.
● Fluridone (Sonar®): The "gold standard." It inhibits pigment production, turning plants white over 30 to 90 days. This slow kill prevents sudden oxygen crashes. Rate: 45 parts per billion, or roughly 4 ounces per acre-foot.
● 2,4-D (Navigate®): Sinks into weed beds in a granular form. Avoid ester formulations (toxic to fish); use amine formulations instead. Rate: 50 to 60 pounds per acre-foot.
Field Guide to Herbicide Application
● No Surfactant Needed: Unlike floating weeds, you want the chemical to disperse into the water, so skip the surfactant.
● Application Techniques: Use subsurface injection (pumping liquids directly under the surface) or broadcast granular forms so they sink to the bottom.
Managing the Primary Risk: Oxygen Depletion
If you kill a pond-wide stand of submerged weeds all at once with a fast contact herbicide, the massive decay process will consume the dissolved oxygen and cause a lethal fish kill.
● The Rule: Treat only 1/4 of your pond at a time. Wait 10-14 days for oxygen levels to recover before treating the next section.
● The Exception: Fluridone, because its 30-to-90-day kill allows plants to decompose gradually.
Water Use Restrictions
Always read the label! While Diquat and Fluridone generally have no swimming/fishing restrictions, irrigation is a different story. Using treated water on your lawn or garden can cause severe collateral damage. (e.g., Fluridone often requires a 7 to 30-day wait, and Flumioxazin requires 5 days).
Alternative & Complementary Management Practices
To stop the cycle of chemical reliance, you must make your pond less hospitable to excessive weed growth.
● Nutrient Mitigation: Address the root cause by reducing fertilizer use near the pond and creating unmowed vegetative buffer strips to filter runoff.
● Aquatic Dyes: Blue or black dyes block the wavelengths of sunlight that submerged plants need. Apply early in the spring for best results.
● Physical Removal: You can use a lake rake, but be warned: Coontail reproduces from fragments. If you fail to remove all the cut pieces from the water, you will actively spread the weed. (It is generally recommended to avoid this method).
● Grass Carp: Results are highly mixed. Carp often prefer other desirable plants and may ignore the Coontail entirely. If you try this, use 6 sterile, triploid grass carp per littoral acre (water less than 6 feet deep).
● The Fertilization Myth: Do not deliberately fertilize your pond to create an algae bloom to "shade out" weeds. This adds fuel to the fire and trades your weed problem for a severe blue-green algae crisis.
Remember, Coontail is a native, beneficial plant. The goal should never be eradication, but rather balanced control. Keep an eye on those nutrient levels, always read your labels, and let's keep those ponds healthy and clear!
If you're more of a visual learner (like myself) click on the link below to watch the video version!
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