Duckweed and Algae

Overview

Duckweed and algae are common aquatic organisms that, when uncontrolled, can create significant challenges for a pond or lake. While small quantities of these are generally safe, these plants’ ability to rapidly grow can quickly make a water feature unusable and potentially harmful for fish and other aquatic life.

Duckweed is a plant and algae are not technically plants. They can grow independently of one another or together, floating on the same body of water. They can also be controlled separately or simultaneously. Read on for descriptions and control options.

Is Duckweed and Algae the Same Thing?

Although duckweed and algae are often found together in ponds and lakes, they are distinctively different. Duckweed is a multicellular plant that absorbs water and nutrients through its roots then photosynthesizes them by using chlorophyll. Algae are single-celled organisms that contain chlorophyll but do not grow stems, leaves, or roots.

Is Duckweed an Algae?

Duckweed is a small, free-floating plant with leaves and roots that dangle in the water. The bright green leaves form in groups of three to five and resemble a small clover. An entire plant can fit on a person’s fingertip. Duckweed flowers and reproduces in groups, but the flowers are only visible with magnification. While duckweed is not considered a type of algae, they both can grow alongside each other.

Types of Green Algae

There are multiple types of algae, including stoneworts, Chara, planktonic, and filamentous. Both planktonic and filamentous categories contain many more specific scientific names for algae. Filamentous algae are the most common types and regularly grow alongside duckweed in lakes or ponds.

Filamentous green algae are stringy and can often be picked up with a stick. These algae begin growing on the bottom or attached to rocks or sticks before they bubble up to float on the surface. They can look like green, slimy clumps or thick mats in the waterFilamentous algae also floats on the surface but are a colony of much smaller organisms that group together.

Where Do Algae and Duckweed Grow?

Duckweed and filamentous algae are common in still waters across the United States. They thrive in nutrient rich environments. Warm water temperatures between 60°- 85° F provide ideal conditions for algae blooms and duckweed growth. In the northern United States, peak season is April- October, middle states is March-November, and southern states is all year long. Competition between algae and duckweed can sometimes result in one dominating the water body entirely. When an overgrowth of either duckweed or algae is removed, sunlight can penetrate deeper, potentially triggering a resurgence of the other, which makes it important to treat both even if there is only a small amount of one compared to the other. Sometimes they coexist without significant competition, both growing aggressively under favorable conditions.

How to Control Algae and Duckweed

How to Control Duckweed

Controlling duckweed effectively requires a targeted approach. Seining the plants from the surface of the water is an option for some. Depending on the physical aspects of the water and the tools and time available, manually removing duckweed from the water every few days can prove successful.

Chemical duckweed control includes the use of herbicides, and Dibrox or Spritflo provide powerful solutions. Dibrox is a fast acting contact herbicide that is diluted with water and sprayed over the treatment area. This broad spectrum herbicide can be used in lakes or ponds. Dibrox gets absorbed into the parts of the plants it touches, then interferes with photosynthesis to stop plant growth, quickly killing the duckweed plants. Results on duckweed will be seen in 5-7 days. Remaining duckweed or new growth can be treated after this time.

Spritflo is designed for ponds with no outflow. It is poured directly into the water and spreads throughout the entire water column. This product needs a longer contact period, producing full results in 30-45 days. It stops the plants from making a protective pigment that keeps chlorophyll from breaking down in the sun, thus preventing duckweed plants from making food for themselves. Spritflo is also broad spectrum and can tackle other nuisance weeds as well. Always read herbicide labels before use.

How to Control Algae IN Duckweed

If the goal is just to control the algae and not duckweed, Mizzen is an effective and easy to use pond algae treatment. Simply dilute and spray this product across the treatment area, much like the Dibrox application. Results on algae will be seen in 7-14 days. After that, re-treat any new algae blooms, and as standard procedure, read the label before application.

How to Control Algae AND Duckweed

Duckweed and algae commonly grow together since their ideal conditions are similar. The key to effective control is using a targeted herbicide to kill both plants completely. The best products for this task are Semera or Flumigard. Both have the same active ingredient, flumioxazin, which controls algae, duckweed, and other weeds.

Semera or Flumigard should be mixed with a surfactant and water then sprayed directly over the plants and algae. Just like Dibrox or Mizzen, results will be seen in 5-7 days on duckweed and 7-14 days on algae. Re-treat any remaining plants/algae after that time. Always read product labels thoroughly before using.

Conclusion

Algae and duckweed can quickly turn a beautiful pond or lake into a murky, unmanageable mess, but with the right tools, control can be regained and balance restored. Duckweed is a floating plant that looks like a small clover with hairlike roots that dangle in the water. Duckweed pond control can be obtained by use of an herbicide such as Dibrox or Spritflo.

Algae are single celled organisms that form on the bottom of the water body and float to the surface in slimy groups. Filamentous algae control can be achieved by use of a copper algaecide such a Mizzen. Semera or Flumigard will address overgrowth for both duckweed and algae. Using these treatments can create a clear, healthy, and beautiful body of water.