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I had a bad duckweed problem last year. How do I prevent it this year? | Ponds & Lakes Q&A

Q: I had a bad duckweed problem last year. How do I prevent it this year?

Q: I had a bad duckweed problem last year. How do I prevent it this year?

Alex – Alvada,OH

A: As you know, Duckweed is a persistent pond pest. 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.

ID Duckweed

Transported by waterfowl, Duckweed is a very small, light green, free-floating plant that sports a single hair-like root and three 1/16- to 1/8-inch long leaves, or fronds, that resemble a four-leaf clover. It tends to grow in dense colonies in quiet water that’s undisturbed by waves, and it’s often mistaken for algae.

Though Duckweed colonies can provide a habitat for microscopic critters and forage for hungry ducks, the plant can wipe out oxygen in the water if it grows to cover a lake’s or pond’s surface. That could compromise your fishes’ health and cut off sunlight to underwater plants.

Plant Pest Control

Because Duckweed is such a small plant that spreads very quickly, it can be difficult to control – and so it’s critical to treat your pond or lake early in the spring when the growth first appears.

To manage these aquatic bad guys, you’ll need an herbicide. We recommend Sonar A.S., a weed killer that provides season-long control against unwanted plants like Duckweed. It’s designed for water bodies that have no water outflow, as it can take 30 to 60 days to control established weed growth and up to 90 days for full protection of your pond.

Sonar A.S. degrades quickly in sunlight, and so you must add Pond Dye at the time of treatment. The dye will shade the water and allow the herbicide to work effectively.

Short-Term Solution

If you want to remove the Duckweed for a short period of time but your pond or lake has an outflow that prevents you from using Sonar A.S., you can remove the tiny plants with the Pond Skim. The floating tool, which is 5 feet wide, collects surface debris when dragged across the water.

Pond Talk: How do you remove duckweed from your farm pond or lake?

One Treatment for the Entire Season - Sonar™ Fluridone 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?

    Controlling Duckweed – Pond & Lake Q & A

    Duckweed

    Ponds & Lakes Q & A

    Q: Duckweed has taken over my pond! What do I do to eradicate it and prevent future outbreaks? – Sue in Michigan

    A: Common duckweed, or Lemna minor, can take over a pond in no time. Growing in dense colonies in quiet, undisturbed water, these tiny free-floating plants, if left unchecked, will blanket a pond or lake over the course of several seasons, depleting the water body of oxygen, destroying fish populations, and killing submerged plants by blocking the sunlight.

    Most often, these green invaders are transported to your pond on the feet of waterfowl, such as ducks, geese or even herons. The plants stick to their feet or feathers and can be carried for miles. Though water fowl and some fish eat duckweed, it typically reproduces faster than the animals can consume it.

    Short-Term Solution

    When controlling duckweed, you can use a fast-acting aquatic herbicide, like PondWeed Defense, to knock down the plant population. The contact herbicide is designed to work best on mature aquatic weeds in a contained environment, and you will need to apply it to the duckweed multiple times for effective short-term control.

    To spot-treat duckweed, mix 1.5 gallon of PondWeed Defense with at least 1.5 gallons of tap water and spray directly on the pond’s surface using the Airmax Pond Sprayer. One gallon will treat 5,000 square feet. To ensure safe oxygen levels, treat your pond in thirds, waiting 10 to 12 days between treatments.

    Long-Term Control

    For longer-term control, use WhiteCap, or Fluridone. It’s the least-expensive method of treating an entire pond, easy to apply, safe for aquatic life and lasts an entire season. The herbicide is absorbed by the leaves, roots and stems directly from the water, and it works by inhibiting the weed’s ability to produce carotene, a pigment that protects the plant’s chlorophyll. Without carotene, the sun quickly degrades the green chlorophyll and the weed dies.

    To treat one surface acre of duckweed in a 4 to 6-foot deep pond, we recommend you mix in a tank sprayer 32 ounces or 1 quart of WhiteCap with enough water to fill the tank. Place the spray nozzle directly under the water and disperse evenly around the pond. It can be applied in early spring before the weed even appears, which means you can get ahead of it before it becomes a problem. Keep in mind that it needs to stay in your pond for up to 90 days, so it’s not recommended to use in ponds with heavy overflow or during times of heavy rain. Also, WhiteCap will be degraded by the sun so we suggest to add Nature’s Blue Pond Dye or Black DyeMond Pond Dye right after treatment to ensure the longevity of the application.

    POND TALK: What kinds of invasive aquatic plants have taken root in your lake or pond? What did you do to control them?

    Controlling Pondweeds: Duckweed – Pond & Lake Q & A – Week Ending March 28th

    Picture of Duckweed Floating in a Pond.

    Pond & Lake Q & A

    Q: Last year I had an uncontrollable case of duckweed in my pond. It covered my entire 1/2 acre pond! I’ve heard of your product called WhiteCap and wanted to use it this spring. I don’t see any signs of duckweed yet, but was wondering if it is too early to treat.
    – Cameron of Michigan

    A: Duckweed can take over a pond. This prolific grower can come from many sources although most commonly brought in on the feet of waterfowl such as ducks, geese or even herons. The small plant can stick to the feet or the feathers of such birds and be carried for miles. Duckweed can start out slow and in some cases take several seasons to become a problem, although I would recommend treating for it as early as possible.

    There are a few options when treating duckweed. You can use a fast-acting aquatic herbicide such as PondWeed Defense or RedWing although this will only give you temporary relief and require multiple applications of spraying the duckweed directly. These are not usually suggested unless your treatment areas are not contained or you have heavy water turnover. When possible I always suggest WhiteCap. WhiteCap is the least expensive method of treating an entire pond, is easy to apply and lasts an entire season.

    We recommend to use 32 oz or 1 quart per surface acre (4-6′ deep) when treating for duckweed. This means Cameron’s 1/2 acre pond can be treated with just 16 oz of WhiteCap!

    To answer the question above, treat with WhiteCap in the early spring before the duckweed even appears. This will allow you to get ahead of it before it reaches the surface. Although you don’t generally see it Duckweed is actually growing at the bottom of your pond long before you see it at the surface.

    There are also other nice benefits to WhiteCap such as: It works very slowly so there is no chance of oxygen loss that could harm your fish or other aquatic life. WhiteCap is also very effective at controlling most other nuisance aquatic plants. So when your treat for your duckweed you will be controlling most other species as well.

    Please Note: WhiteCap needs to stay in your pond for up to 90 days. It is not recommended to use it in ponds with a heavy overflow or when during times of heavy rain. If you are unsure of your pond’s turnover (or amount of water that is exchanged) use Nature’s Blue Pond Dye to shade the water column and track the time it takes for the color to disappear. You may also use Nature’s Blue Pond Dye during a WhiteCap treatment to track turnover and shade the pond from sunlight which can also reduce the life span of WhiteCap.

    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 is to use a product called Sonar™ A.S.. The best way to get rid of watermeal is to use a product called Clipper™. Sonar™ A.S. 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.

    Both Sonar™ A.S. and Clipper™ 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 these herbicides and the aquatic weeds they will control, click here.

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