The Management Decision: When Is Control Warranted?
Before considering coontail control, the management team must honestly evaluate whether control is warranted. Coontail is a native plant with significant ecological value — providing fish habitat, waterfowl food, and invertebrate community support. Management is appropriate when coontail has reached densities that cause meaningful ecological or recreational harm that outweighs these benefits. It is generally NOT warranted simply because coontail is present, or when it occupies less than 20–30% of a water body's littoral area at moderate density. Control is most clearly warranted when: coontail forms near-complete surface-to-bottom mats across most of the littoral zone; when it is causing documented oxygen depletion; or when its density has displaced all other native plant diversity and the management goal includes restoring plant community diversity. All aquatic herbicide treatments require state permits.
Management Philosophy: Unlike invasive species management, coontail control should target a reduction in density rather than elimination. Preserve sufficient coontail for ecological function while addressing the specific harms caused by excessive density. Work with your state DNR to ensure management goals and methods are appropriate for your water body.
Addressing the Root Cause: Nutrient Reduction
Dense coontail growth is almost always a symptom of eutrophication — excess nutrients (primarily phosphorus and nitrogen) from human activities driving plant growth beyond what the ecosystem can balance through grazing and natural limitation. Nutrient reduction is the single most important long-term management action. Without addressing the nutrient driver, coontail will regrow after any control treatment, and the same management challenge will recur annually. Nutrient reduction strategies include eliminating fertilizer runoff through buffer strips and application management, reducing stormwater nutrient inputs, addressing internal nutrient loading through alum treatment or aeration, and managing livestock access to water bodies. See how nutrients drive aquatic weed growth for background.
Mechanical Control
Mechanical harvesting is the most ecologically sound immediate management tool for nuisance coontail because it removes biomass without chemical inputs, preserves the option for immediate reuse of treated areas, and can be targeted to specific areas rather than whole-water-body treatment. Properly equipped aquatic harvesters cut and convey coontail biomass from the water. Because coontail is rootless and free-floating, it can be harvested efficiently — cut stems rise freely to be conveyed to the harvester without extensive fragmentation. All harvested material must be removed from the water body and composted or disposed of on land. Mechanical harvesting requires repeated treatment during the growing season because coontail regrows rapidly from stem fragments not captured by the harvester.
Herbicide Treatment
Several aquatic herbicides are registered for coontail control, but the decision to use herbicides against a native plant requires careful consideration of impacts on the broader plant community and the ecological services being managed:
Fluridone (Sonar)
Fluridone at whole-pond concentrations will suppress or eliminate coontail along with other aquatic vegetation. It is non-selective (affecting most plant species) and requires 60–90 days of maintained concentration. Best reserved for situations where coontail has displaced all other vegetation and restoration of a more diverse native plant community is a management goal — fluridone treatment followed by native plant reintroduction may achieve this.
Endothall (Aquathol)
Endothall can be applied as a contact treatment for coontail spot control. It acts quickly and breaks down relatively rapidly, minimizing impacts on adjacent areas not targeted for treatment. Useful for spot-treating dense patches in areas critical for navigation or recreation while avoiding treatment of areas where coontail provides important habitat.
Diquat (Reward)
Diquat is a fast-acting contact herbicide that provides rapid knockdown of coontail biomass. Similar to endothall in its application profile for spot treatments.
Water Level Management
Fall water drawdown that exposes the shallow littoral zone to freezing temperatures can significantly reduce coontail density. Coontail has no tubers or other cold-resistant overwintering structures — the plant survives winter as living stems in the water column, and exposure to freezing and drying kills it. Drawdown must lower water levels enough to expose the coontail-bearing shallow zone (typically 0–2 feet) to sustained freezing temperatures. Refilling in spring before the growing season allows management of coontail density while minimizing chemical inputs. This is most applicable in regulated lakes and impoundments with controllable water levels. For management planning guidance, see the management planning hub.
References
- Nichols, S.A. (1991). Biology and management of aquatic macrophytes. Aquatic Botany 41:225–252.
- Wisconsin DNR. Coontail Management Guidelines. dnr.wi.gov