(Egeria densa)

Total Control Pest

Egeria is a vigorous, submerged, aquatic perennial that can grow to 5 metres tall in still water. The leaves are dark green, up to 4 centimetres long, in whorls of four to six. It has white flowers, conspicuously protruding just above the surface, up to 20 millimetres in diameter. It spreads through shoot fragments, a process often aided by humans.

Reasons for the Strategy

The white flowers of Egeria poking out above water.

Egeria can form extremely dense stands that reduce water flow. It is very effective at suppressing other aquatic species, including natives, degrading the natural character of rivers and lakes. It restricts water traffic and interferes with recreational activities. It also impedes irrigation, water supplies and hydroelectricity operations.

Egeria is assessed at “1” on the infestation curve. There are a small number of known sites in garden ponds in the Tasman-Nelson region, but it is likely that there are infestations in other ponds in the region. The low incidence of Egeria in the Tasman-Nelson region, extensive areas of suitable habitat, and the potential for it to cause significant adverse effects, mean the benefits of total control far outweigh the costs.


To contribute to the eradication of Egeria by ensuring that all known sites in the Tasman-Nelson region are inspected annually and all live plants are destroyed during the term of the Strategy.

Alternative Measures

The alternative option of “do nothing” or relying on voluntary control will not achieve the objective of eradication, and will result in significant additional costs to the community with respect to lost natural values and the increased cost of control in the future.

Strategy Rule for Egeria

The occupier shall destroy all adult and juvenile forms of Egeria on land that they occupy. A breach of Strategy Rule 4.6.5 is an offence under Section 154(r) of the Biosecurity Act 1993.

Biosecurity Act Requirement

No person shall knowingly sell, propagate, breed, release, or commercially display Egeria, under Sections 52 and 53 of the Act.