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How can I control the duckweed in my pond? | Ponds & Lakes Q&A

Q: How can I control the duckweed in my pond?

Q: How can I control the duckweed in my pond?

Kyle – Burke, KY

A: Duckweed is a tiny menace that definitely needs to be managed. Brought to your pond or lake by humans and their equipment or on the feet and feathers of visiting waterfowl, dense colonies of these plants can proliferate and eventually cover the water surface. It’s not something you want in growing your pond.

Duckweed or Watermeal?

Duckweed a very small, light green, free-floating plant with a single hair-like root and three 1/16- to 1/8-inch long leaves, or fronds. It tends to grow in dense colonies in quiet water that’s undisturbed by waves. You can fit six to eight of these plants of the tip of your finger.

Watermeal – another invasive plant that can be mistaken for duckweed – is also light green and free-floating, but it has no roots and is more of a grainy, seed-type plant. It’s also much smaller than duckweed; at less than 1 millimeter in size, you can fit 10 to 20 of them on the tip of your finger.

Duckweed and watermeal colonies can provide a habitat for microscopic critters and forage for hungry ducks, but the plants can reduce oxygen in the water if they grow to cover a lake’s or pond’s surface. That could compromise your fishes’ health and cut off sunlight to underwater plants.

Treat Effectively

To control duckweed, think short-term and long-term.

Short Term: Ultra PondWeed Defense® or Clipper™ used with Treatment Booster™ PLUS are your go-to herbicide products for short-term control of duckweed and other invasive aquatic weeds. They provide broad-spectrum pond weed control in slow-moving water and kill what’s actively growing in your pond. If duckweed hasn’t completely taken over your water surface, you may notice algae growth mixed in with the weeds – in which case you’ll need to treat the algae first. (Pro tip: Clipper™ will control both algae and duckweed.)

Long Term: For long-term control, you’ll need an herbicide like fluridone, which is found in Sonar™ A.S. When applied in early spring (or when you begin to notice weed growth), you’ll see the product controlling established plants in 30 to 60 days, and in 90 days, you’ll have full pond protection. Because exposure to sunlight can reduce Sonar’s effectiveness, use in combination with Pond Dye. If you use your pond water to irrigate, you will need to wait 30 days following treatment.

Improve Overall Pond Health

In addition to managing your menace with herbicides, you should also reduce muck and aerate the water to keep your overall pond healthy. The products in the ClearPAC® PLUS Pond Care Package – including PondClear™, MuckAway™ and EcoBoost™ – will help reduce the submerged and suspended organic debris. Combine that with some Airmax® Aeration, and your water will stay crystal clear all season long.

Pond Talk: What else do you do to control duckweed in your lake?

Treats Floating & Submerged Weeds - Valent® Clipper™ Aquatic Herbicide

How do I know which chemicals will treat my weeds? | Ponds & Lakes Q&A

Q: How do I know which chemicals will treat my weeds?

Q: How do I know which chemicals will treat my weeds?

Henry – Markesan, WI

A: Weeds. Whether they’re algae or submerged, floating or shoreline plants, they’re a nuisance—not to mention a potential hazard to your game fish and pond or lake health. In order to manage these green invaders, you should get to know them a little better. Don’t worry: you don’t need to be a Master Gardener to identify and treat them. Here’s all you need to know:

1. Know the Weeds

Before you start dumping chemicals on the weeds in your pond, you’ll first need to understand the different types of aquatic weeds that pop up in lakes or ponds. There are four basic categories:

  • Algae. Algae comes in three basic types: Planktonic, which causes the pea soup look in your water; filamentous, which creates blankets of stringy stuff or pond scum; and chara or muskgrass, which smells like musky garlic. When you take a closer look, these weeds have no defined root systems, unlike their other weed cousins.
  • Submerged. Submerged weeds live underwater. This group of troublemakers includes bladderwort, several types of pondweed, watermilfoil, parrot feather and hydrilla. They look like a typical plant, with leaves, stems and root systems.
  • Floating. Floating weeds generally reside in shallow water and have root systems that reach into the water or down into the soil, allowing their leaves and flowers to rise to the surface. They include watermeal, duckweed, azolla and even water lilies. When not kept in check, these floaters can take over a pond in no time.
  • Emergent. Emergent weeds live along your lake’s shoreline. These plants like to keep their feet wet; their foliage, leaves and flowers live out of water, but their root systems prefer wet, almost completely saturated soil. Emergent weeds include cattails, phragmites, purple loosestrife and bulrush.

2. ID the Weed

Once you identify the category of weed you’re dealing with, head over to our Weed Control Guide and try to match weed with the picture. For example, is it a floating plant with a root system? Then you’re dealing with a type of floating weed. Is it completely submerged? Then you’re dealing with a type of submerged weed.

Each weed included in our Weed Control Guide will describe the best treatment options to manage it. Not sure of the weed? Snap a close-up photo and e-mail it to us at weedid@thepondguy.com. Of course, you can always call us toll-free for advice, too, at 866-POND-HELP (766-3435)!

3. Treat the Weed

Once you’ve ID’d the weed, treat it with its appropriate herbicide, remembering to always follow label instructions when applying it to your pond or lake. If you have fish in your pond, we suggest treating in sections as sudden changes in water conditions can affect aquatic species. Treat 1/4 – 1/2 of pond at a time, while waiting 10-14 days between treatments.

4. Remove the Remains

Once the chemicals start working to kill the weeds, make sure you remove the decomposing foliage with a weed rake, like the Jenlis Weed Razer™ Aquatic Weed Cutter. Why? Because anything dead will turn into muck and start the weed/algae cycle again—which is not something you want to happen, right?

Pond Talk: What tips do you have for managing aquatic weeds?

Broad Spectrum Pondweed Control - Pond Logic® Ultra PondWeed Defense®

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