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Late summer cattail and floating-leaved plant control for ponds

Have the cattails in your pond taken over your favorite fishing spot or crowded you from one side of the dock or swimming area? 

Late summer or early fall is the best time to kill cattails, Lotus lily and other emergent or floating-leaved plants that are on the pond’s edge or are above the water. Spraying herbicides this time of year will kill the entire plant, and it will not regrow next spring. Since these plants die-back every year at this time and decompose slowly over the coming months, there is little risk of depleting the oxygen in the pond with treating these plants.

Starting in late summer, these plants move food to their roots to survive the winter, making systemic herbicides most effective. The most common active ingredient to use is glyphosate (a few brand names with labels for aquatic use include Aqua Neat, Aqua Pro, Aquamaster, GlyphoMate 41, Pond Master, Rodeo, Shore Klear and Touchdown Pro). Find these at local hardware, farm supply or garden stores or try an online search for “aquatic glyphosate.”  

Many of these herbicides need a surfactant or spreader-sticker added to the mix to help it stick to the plant’s leaves.  Read the label and check with your local or online retailer to select a surfactant that you can use in ponds.  Spray the above-water portion of the plant until just wet and follow other instructions on the product label.

When you compare product brands, consider the amount of active ingredient, if a surfactant is needed, and size of the container. A product with a higher amount of active ingredient or one that does not need a surfactant added may provide a better value.  The convenience of a ready-to-use (RTU) product that you do not have to mix or add a surfactant may outweigh price considerations. 

Be careful to:

  • Always read and follow the product label for application instructions and precautions.
  • Spray when calm, or when winds are low and out of a favorable direction to avoid accidentally spraying other plants valuable to landscaping.  Increase the droplet size of the spray to reduce drift. 
  • Spray early in the day with full sunlight to get the best results.
  • Obey State law.  Shoreline owners on public waters may not use herbicides to control aquatic vegetation without a permit.  Contact the DNR fisheries office near you for rules and instructions for removing vegetation from public waters.

Learn more about aquatic plants in ponds at www.iowadnr.gov/pondplants.

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