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Controlling Emergent Weeds – Pond & Lake Q & A

Picture of cattails with a pond in the background.

Pond & Lake Q & A

Q: What do I use to kill the emergent weeds on the shoreline? What sprayer should I purchase? NOTE: My kids swim in pond. – James of Wisconsin

A: At first sight or when controlled properly, cattails and other emergent weeds can add natural beauty, structure for fish and act as a buffer to reduce nutrients and sediment caused by runoff. But, beware! Emergent weeds can take over a pond very quickly if left alone for too long. It is best to pick an area of emergent weeds that you are acceptable with and mark it with boulders or other pieces of landscape. This will allow you to control only the emergent weeds that grow outside your acceptable boundary. There are 3 simple steps to control emergent weeds: 1) Spray… 2) Cut… 3) Repeat…

1.) Spray – Select the best product for the job. Shoreline Defense® & Treatment Booster™ PLUS Combo is best at providing long-term control for all types of grasses and cattails. It will also work for phragmites and/or purple loosestrife. Shoreline Defense® & Treatment Booster™ PLUS are mixed together with water and sprayed directly on to the target plant with a tank sprayer (We suggest using the The Pond Guy® Pond Sprayer). This will allow you to control all areas or select areas that you have set aside for this type of growth. Also note: Shoreline Defense® & Treatment Booster™ PLUS have no swimming use restrictions.

2) Cut – Emergent weeds can sometimes have a root base deep within the ground so removing them before they are completely dead will allow them to come back very quickly. Most emergent weeds are best treated when the foliage is around 12″ high. This will allow enough contact for the aquatic herbicide. After a successful treatment, they will turn brown and become limp within 7-14 days. After this occurs, use an Aquatic Weed Cutter to cut the weeds at their base and then simply rake them out with the Pond & Beach Rake.

3) Repeat – Repeat these steps as necessary. In some cases it may take several applications to gain control.

9 Responses

  1. I work at a non-profit and we have a large aquatic weed cutter that we have used in our lake, but we have no use for it now. Where can i sell it?

  2. […] Treat and remove emergent plants such as cattails that allow water to become stagnant around your shoreline. (Read More Info on Removing Emergents) […]

  3. Ken Yelle,

    Yes there are long term problems with this! Karmex (Active ingredient: Diuron) is an extremely bad chemical to use in your pond. Not only is very illegal to use in and around your pond, it is hazardous to your health as well! Karmex has been shown to cause cancer, and is very capable of entering the groundwater that runs underneath the pond causing problems with the neighbors as well.

    The biological effect is substantial. Karmex will kill almost every plant touching the pond. While this seems like a great idea, the problem lies in the few things that survive. These survivors are extremely hardy, and honestly if Karmex wouldn’t kill them, nothing will. Eventually these plants will take over the pond, and there is not much you can do to stop it.

    Karmex is a soil sterilant that was disigned to kill farm fields where no chance of runoff will occur. Sadly, many small stores and elevators sell it as a pond product, not knowing how extremely bad this chemical is for humans and the environment.

    Avocet and Kraken are approved aquatic chemicals that will kill the plants around your pond in a safe and less environmentally harsh way. Stick with them and you’ll find yourself much better off in the long run.

  4. Nancy Grimm,

    For duckweed I would refer to this post (Controlling Duckweed & Watermeal). It talks about how to use WhiteCap to control duckweed.

    Hope this helps!

  5. Wade Melton,

    To kill water lilies the best product to use, if you don’t have to irrigate, is called Kraken. We highly suggest to mix Kraken with a surfactant called Cide-Kick for best results. Cide-Kick will allow the aquatic herbicide to be absorbed by the water lilies better for optimum control. To treat approximate 2,500 sq. ft. we recommend mixing 4 oz Kraken, 2 oz Cide-Kick Surfactant & 1.5 Gal water into a tank sprayer. Spray to completely wet the leaf surface of the water lily. The above is a recommendation, I would always suggest to read the kraken label. If using your pond water for irrigation, another option would be to use Avocet. The dosage rate is a little different, but the same concept. You would use 8 oz Avocet, 4 oz Cide-Kick & 2 gal water.

    Hopefully this helps you Wade!
    Thanks for your question.

  6. I would like to find something to kill water lillies

  7. Thnks for this information…but I do not really understand what/when to use to use for duckweed which lays on the top of the pnd, grows very rapidly and covers the entire surface.

  8. I use Karmax powder to kill all my weeds on the banks of my pond. Is there any long term problems with this?

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