Opposite-leaved pondweed

Opposite-leaved pondweed (Groenlandia densa) is an aquatic plant belonging to the Potamogetonaceae family. It is a submerged perennial that acts as a significant weed in various hydro-engineering structures. Unlike typical pondweeds, it is categorized as a monotypic genus.

This weed is commonly found in slow-moving streams, ponds, and drainage or irrigation canals. In an agricultural context, it is considered a pest primarily due to its ability to clog irrigation networks, affecting water distribution in paddy fields and managed wetlands.

The biology of this species is characterized by aggressive vegetative growth. It forms dense, submerged mats that significantly reduce water flow speed. The plant thrives in diverse aquatic environments, making it highly adaptable and difficult to eradicate once established in a system.

The damage caused by this plant is mainly related to hydraulic obstruction. By slowing down the current, it promotes sediment deposition and siltation, which drastically reduces the carrying capacity of irrigation canals and requires frequent and costly maintenance.

Control measures rely on a combination of physical and chemical methods. Mechanical removal (dredging and mowing) is the most common approach to keep channels clear. Chemical control must be managed carefully using herbicides approved for aquatic use to prevent damage to the surrounding environment.

• Regular mechanical clearing of irrigation channels.
• Drying out canal beds during the off-season.
• Targeted use of aquatic-safe herbicides.
• Monitoring water intakes to prevent spread to new fields.