A Black Lagoon Case Study: Managing Duckweed in an HOA Pond

A photo of the pond during the initial site inspection; Photo courtesy of Benjamin Pollock, Aquatic Specialist

Applicator’s Notes: Located in Gloucester County, New Jersey, this 2/3 of an acre stormwater management pond is the focal point of this affluent community. Upon site inspection it was determined that the pond was significantly infested with Duckweed, Lemna minor, which presented a major aesthetic concern for the residents, especially those who lived on the water. A relatively shallow waterbody with a history of low dissolved oxygen, and a large warmwater fish population.

What is Duckweed: Common Duckweed, Lemna minor, is one of the smallest flowering plants on the planet. This small, easily distributed, floating plant can be found throughout most of the United States and Canada (excluding Hawaii and South Carolina), in slow moving or still waterbodies. Currently there are nine subspecies, which makes identification of individual species difficult. Despite its small size, the flowers can attract bees which use the plant’s pollen. A rapid grower, this plant can quickly cover a waterbody, serving as a food source to waterfowl and fish, but can become a nuisance to humans. Though duckweed can be a nuisance to the residents of a pond, scientists are using small plant as a bioremediation tool for waterbodies with increased amounts of phosphorous and nitrogen.

Despite its diminutive size, Duckweed can rapidly reproduce and become a nuisance in small ponds

Success Story: With a late start to the management of the pond (July) and the already substantial population of duckweed, the decision was made to use a systemic aquatic herbicide. In conjunction with the herbicide treatment of the pond, the decision was made to add a floating fountain to aid in the treatment and provide beneficial supplemental aeration. With a management plan and objectives in place, and original application performed, monitoring of the pond began to observe the effects of the treatment. 40 days after the initial treatment, no signs of duckweed were observed, and we are left with very satisfied clients! Management of the waterbody will continue to ensure that all aquatic vegetation and algae is kept below nuisance levels.

40 days after initial treatment, the pond is free of Duckweed