What does it look like?
Salvinia is a free-floating aquatic fern that forms large, dense mats. With its hairy leaves and ability to float, it can be hard to recognise as a fern. The spongy leaves are green to bronze, up to 5cm long, and their shape varies with the age.
Young, small leaves lie flat on the water surface, but mature leaves tend to become crowded and fold up. The upper surface of the leaf is water repellent and covered with distinctive white hairs and an eggbeater like tip. Salvinia has no true roots but has a root-like structure underneath each leaf pair.
Salvinia grows on wind-protected ponds, small lakes, artificial waterbodies (e.g. dams and reservoirs) and swampy backwaters. It grows best in nutrient enriched waters but can survive in frequently inundated, damp mud.
Why is it a problem?
Salvinia quickly forms extensive mats, completely smothering waterways. It can double in area within 10 days. The mats exclude native plants, block dams and waterways, impede drainage, disrupt recreational activities and reduce water quality by lowering oxygen levels.
The large mats also create a drowning risk for people and animals. The only conditions that are not suitable for salvinia are in cooler seasons, extreme shade or frosty mornings in winter, where the species can suffer from 'winter die-back'.
In New Zealand, salvinia does not produce spores. It spreads vegetatively from plants and plant fragments.
Control methods
The salvinia eradication programme consists of containing the infestation to an area, removing plants and/or applying herbicide treatments, and monitoring for 2 to 5 years after the last plants are detected (depending on site complexity), to ensure no viable plant material remain.
Related links
- https://www.mpi.govt.nz/outdoor-activities/boating-and-water-activities-preventing-the-spread-of-pests-weeds-and-diseases/check-clean-dry-for-the-north-island/
- Freshwater invasive species of NZ
- https://www.mpi.govt.nz/dmsdocument/3580/direct
- http://www.nzpcn.org.nz/flora_details.aspx?ID=2664
- https://www.mpi.govt.nz/biosecurity/long-term-biosecurity-management-programmes/national-interest-pest-responses-programme
- http://www.nzflora.info/factsheet/Taxon/Salvinia-xmolesta.html
- http://apps.mpi.govt.nz/applications/nzpests-view/Article/561/Salvinia
- https://www.weedbusters.org.nz/what-are-weeds/weed-list/salvinia
- National Interest Pest Responses programme
- How you can help get rid of salvinia and water hyacinth
Notify Council
If you think you've found this pest, please get in touch with our Biosecurity Team at biosecurity@hbrc.govt.nz or call us on 0800 108 838.
Management Programme
National Pest Plant Accord (NPPA)
The NPPA is designed to prevent the sale, distribution and propagation of a set list of pest plants (the Accord list) within New Zealand. If allowed to spread further, these pest plants could seriously damage the New Zealand economy and environment.
More informationUnwanted Organism
An unwanted organism is any organism that's capable of causing harm to natural or physical resources (like forests and waterways) or human health. A number of introduced pests in New Zealand are classed as unwanted.
National Interest Pest Responses programme (NIPR)
Nine harmful weeds are managed under the National Interest Pest Responses (NIPR) programme. These pests could cause serious harm to New Zealand's environment and economy if they are allowed to spread.
More informationNotifiable Organism
Some organisms must be notified to MPI if they're spotted in New Zealand. These include serious pests and diseases like foot-and-mouth disease, the rabies virus, fruit fly and disease-carrying mosquitoes. If a notifiable organism established in New Zealand, it could severely affect our primary production or trade and market access. If you spot a notifiable organism, you have a legal obligation under section 44 of the Biosecurity Act 1993 to tell MPI. Call the pests-and-diseases hotline on 0800 80 99 66.
The Biosecurity (Notifiable Organisms) Order 2016 lists notifiable organisms. New additions can be made by the Governor-General and MPI periodically reviews the list to ensure it is up-to-date.
Taxonomies
FamilySalviniaceae
TypePlants
GroupFloating
HabitatFreshwater
Management ProgrammeNational Pest Plant Accord (NPPA)Unwanted OrganismNational Interest Pest Responses programme (NIPR)Notifiable Organism
