Common duckweed

Common duckweed (lat. Lemna minor) is a perennial aquatic plant belonging to the Araceae family. In agronomy, it is classified as an invasive aquatic weed characterized by extremely rapid vegetative reproduction. The plant consists of tiny leaf-like fronds that float on the surface of water, lacking distinct stems or leaves, but possessing small rootlets that hang into the water column.

This weed is found worldwide in still or slow-moving freshwater bodies, irrigation channels, and flooded rice fields. In agricultural settings, it is a problematic weed that can form a dense, uniform mat across the entire water surface, significantly disrupting the aquatic environment and interfering with farming operations.

The biology of Lemna minor is marked by its rapid colonizing ability. It reproduces primarily through budding, where daughter fronds separate from the mother plant. This plant thrives in nutrient-rich water, efficiently absorbing nitrogen and phosphorus, which allows it to cover vast areas in a very short amount of time when conditions are optimal.

The economic harm caused by common duckweed is primarily due to its physical presence. By covering the water surface, it blocks sunlight from reaching submerged aquatic life and prevents gas exchange between air and water, leading to hypoxia. In rice production, it competes with crops, impairs water temperature regulation, and creates physical obstacles that block irrigation flow.

Effective control measures include a strategic combination of methods:

• Mechanical removal: physical clearing of the mats using netting, rakes, or mechanized skimmers.
• Agrotechnical measures: maintaining steady water flow in irrigation systems to prevent stagnation and colonization.
• Chemical control: applying aquatic-approved herbicides that selectively target floating weeds while minimizing impact on other species.
• Biological control: introducing fish species, such as grass carp, which are known to consume large quantities of duckweed, helping to keep populations under control.