Duckweed Problems

Duckweed grows in dense colonies that can harm other plants and animals.

Duckweed is a type of tiny, free-floating plant found on the surface of ponds and other still and slow-moving bodies of water. Despite its small size, duckweed grows in large, dense colonies that can harm the plants and animals in its habitat.

Identification

There are over 40 species of duckweed, according to Environmental Inquiry, a website associated with Cornell University and Penn State. Each plant has one or more fronds--leaf-like structures composed of both leaf and stem--and roots that dangle below the water.

Threats

Duckweed reproduces rapidly through budding, a process in which new fronds sprout from the parent plant, develop roots and detach. Left unchecked, duckweed colonies can cover an entire pond surface within a few weeks, says Carole Lembi, a botany professor at Purdue University. This depletes the oxygen supply and prevents sunlight from penetrating the water, killing other plants and fish.

Prevention/Solution

According to Lembi, herbicide use is the most effective way to control duckweed. Two such chemicals are diquat and fluridone. Diquat kills on contact; however, it wears off quickly, making multiple treatments a necessity. Fluridone is pricier, but tends to be more effective thanks to its ability to remain in water for up to 30 days. Non-chemical control options include skimming or draining the infested body of water.

References

• Aqua Plant: Common Duckweed
• Environmental Inquiry: Duckweed
• Purdue: Duckweed Prevention and Control