A dense surface cover of water lettuce can restrict stock access to water, increase water loss by transpiration, and impede drainage and navigational. It can also block water supply inlets, dam waterways, cause flooding, and prevent recreational use of water ways. This stolon production is repeated by each daughter stem. Dislodged plants are spread by waterflow and intentionally by humans. Seeds are normally spread by water action.
Eradication is achieved by way of hand clearance.
It is an offence for anyone to grow this plant. Class A Noxious Plants are deemed to pose an intolerable threat to NZ and must be eradicated. The government pays for and organises all eradication work needed on this plant. It is thought that water lettuce, a native of South America, was originally brought into New Zealand for decorative use, in 1973. It was known from only one field site in New Zealand, in thermal water at Welcome Bay, Tauranga, and it is now though to have been eradicated from all aquaria in New Zealand.