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I think I have duckweed or watermeal. How do I know? And how do I treat it? | Ponds & Lakes Q&A

Q: I think I have duckweed or watermeal. How do I know? And how do I treat it?

Q: I think I have duckweed or watermeal. How do I know? And how do I treat it?

Richard – Fishers, IN

A: Duckweed and watermeal are both pond pests. Dense colonies of these prolific plants can completely cover the surface of a lake or fish pond, causing dissolved oxygen depletions and fish kills. These tiny invaders need to be managed before they take over.

But before you control them, you need to get to know them. Let’s meet these troublemakers.

Watermeal

The smallest seed-bearing plants in the world, watermeal is a very tiny (less than 1 millimeter) light green free-floating rootless plant that resembles green cornmeal. They prefer quiet water that’s undisturbed by waves, and they’re often associated with colonies of duckweed and mosquito fern (azzola). Unchecked, these plants can be aggressive invaders.

Duckweed

Duckweed is another very small light green free-floating plant, but unlike watermeal, duckweed has a single root and one to three leaves, or fronds, that measure 1/16- to 1/8-inch long. Like watermeal, duckweed tends to grow in dense colonies in quiet water that’s undisturbed by wave action. Duckweed colonies provide habitat for micro invertebrates, but if it completely covers the surface of a pond for an extended period, it will cause oxygen depletions. As its name implies, duckweed is often gobbled by ducks, which also transport it to other bodies of water but you cannot count them for keeping the weed in control.

Stop the Invasion!

To control these aquatic bad guys, you’ll need a herbicide. Clipper™ and Ultra PondWeed Defense® are both selective plant killers that will attack watermeal and duckweed. They’re a short-term solution for both—be sure to apply as directed.

For long-term control of duckweed, you’ll need something a bit stronger. We recommend Sonar™ A.S.. It’s formulated to control stubborn aquatic weeds all season long. Don’t forget to add pond dye, it protects the Sonar™ A.S. from being quickly degraded by the sun.

Pond Talk: Tell us about your experiences with duckweed and watermeal. Do you have any additional management tips to share?

Deliver Fast & Selective Control Of Weeds - Valent® Clipper™ Aquatic Herbicide

How do I control floating and bottom-growing algae in my lake? – Pond & Lake Q & A

No Algae Here!

Pond & Lake Q & A

Q: How do I control floating and bottom-growing algae in my lake? – Tom in New York

A: Whether it’s floating or submerged, algae can turn a lake into a green mess in no time. It’s unsightly, it’s sometimes stinky and in extreme cases, it can cause a fish kill. The good news is that algae can be controlled no matter what time of year. It starts with controlling the population and ends with a long-term management plan.

Before we dive in, it’s important to understand the difference between algae and weeds. The term “algae” refers to a wide range of single and multi-celled organisms that live in the water and metabolize carbon dioxide into oxygen via photosynthesis, just like plants. They differ from plants or weeds in that they don’t have true leaves, roots or stems.

In lakes and ponds, the most common varieties of algae include: Green floating algae that creates a “pea soup” appearance; Chara or Stonewort, which are a bottom-growing, seaweed-looking type that can be mistaken for weeds, and string or filamentous algae, which are actually long strings of algae connected together.

Sometimes, pond and lake owners may mistake duckweed for floating algae, but if you look very closely, you’ll find that it’s actually duckweed or watermeal. Check out this blog entry to learn more about controlling this invasive weed.

Population Check

If your pond is coated in pea soup or the bottom is carpeted in Chara or string algae, you can knock back the population with a chemical herbicide like Algae Defense®. It provides quick results and it’s formulated to get a pond under control – especially during the hot summer months. Do not use if your pond or lake is stocked with koi or goldfish. If your pond has trout, check your carbonate hardness with a water hardness test kit, like the Laguna® Quick Dip Multi-Test Strips, and make sure the carbonate hardness is above 50 parts per million (ppm) before using Algae Defense®.

Long-Term Strategy

Algae Defense® by Pond Logic® will solve a crisis, but to keep your pond or lake looking clean and clear, you’ll need to be proactive and develop a plan to manage the algae. The most successful approach centers on cutting off the algae’s food supply – nutrients.

Nutrients can come from a wide variety of sources, like grass clippings, twigs, trees, fish waste, yard and farm fertilizers and runoff. As these nutrients break down, they produce ammonia, which triggers the nitrogen cycle. Nitrifying bacteria surround the ammonia, turning it into nitrites and then into nitrates (nutrients) – which then feed the algae.

So, how do you reduce the nutrients in your pond?
Try these tips:

  • Buffer before fertilizing: To prevent inadvertently fertilizing the algae, leave a buffer area around the pond. You can also try using organic or low-phosphorus fertilizers.
  • Aerate, aerate, aerate: Because that muck at the bottom of the pond feeds the algae, you should prevent the buildup with proper aeration.
  • Reduce the muck: Use natural bacteria like MuckAway™ by Pond Logic® to breakdown up to 5-inches of organic muck per year. You can also rake your pond using a Pond & Beach Rake to remove dead vegetation, leaves and other organics that will eventually decompose on the bottom.
  • Reduce sunlight: Like all photosynthetic organisms, algae requires sunlight to thrive. Adding pond dye can help provide shade. If possible, consider adding some non-invasive aquatic plants to your pond. The plants, which also consume nitrates, will also be a source of competition for food.
  • Add beneficial bacteria: You may also consider adding some additional beneficial bacteria, like PondClear™ by Pond Logic®, to your pond or lake. The bacteria gobble through nitrates, breaking down fish waste, leaves and other organics that accumulate in the pond, naturally improving the water clarity.
  • That green gunk can be controlled in your pond or lake. It just takes a little planning and some proactive management. When you see the results, it’ll be worth it!

    POND TALK: When was your worst algae bloom and how did you control it?

    There is an Oil Slick Film Covering My Pond. How Do I Get Rid of It? – Pond & Lake Q & A

    Algae, Duckweed, Watermeal & Pollen Identification

    Q: There is a brown rust-like film/oil slick covering my pond. Do you have an idea what this might be and how to get rid of it? - Several Customers

    A: There are several things this could be: Algae, duckweed, watermeal or pollen.

    Determining if Algae is a Problem: Filamentous Algae will float around the pond’s edges in mats while Planktonic Algae will make the whole body of water to look like a “pea soup” green color. If this is the case, using Algae Defense Algaecide will provide quick control. Follow up with Pond-Clear for long-term clear water.

    Determining if Duckweed or Watermeal is the Problem: Duckweed and Watermeal are very rapid growers and will cover an entire pond if they get out of control. Looking to the pictures to the left, you can see that Duckweed is a small plant the size of a pencil eraser, while Watermeal is about the size of the tip of a pencil. If you determine that you have Duckweed or Watermeal, your only long-term option is WhiteCap Aquatic Herbicide. If you only require short-term control (3-4 weeks) for an event or party PondWeed Defense may be used.

    Determining if Pollen is the Problem: What may look like a greenish, brownish algae, may actually be pollen. Pollen may even cause an oil-slick or film on the surface of the pond. There is no magic product that will give you a quick fix. Many times a heavy rain will settle it to the bottom. In many cases if your pond receives good circulation from an aerator or fountain you will not see pollen becoming much of a problem.

    Controlling Duckweed & Watermeal – Pond & Lake Q & A

    Q: I think I have duckweed and watermeal. It’s taking over my pond! I can’t seem to get ahead of it! What do I do?
    - Several Customers

    Picture of DuckweedA: Duckweed and watermeal are very prolific growers and can cover a pond before you know it. When covering a pond it can look like algae, but up close you can see it’s not (see pictures on the left). You can try to rake the duckweed and watermeal off the pond’s surface but more will be back within the week. The absolute best way to get rid of duckweed and watermeal is to use a product called WhiteCap. WhiteCap works by inhibiting the weed’s ability to produce carotene. Without this ability, chlorophyll is rapidly degraded by sunlight and the weeds die. The only water use restriction is a 30 day irrigation restriction.

    WhiteCap will also get rid of many other submerged weeds in the pond and will produce season-long results in as little as 30-45 days.

    Picture of WatermealFor more information on Whitecap and the aquatic weeds it will control, click here.

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