Salvinia
Common name: Salvinia
Botanical name: Salvinia molesta
Management programme: National Interest Pest Response led by Biosecurity New Zealand (a business unit of the Ministry of Primary Industries).
17 March 2023
Salvinia weed find at old Waihī Beach reservoir
An infestation of the invasive aquatic weed salvinia (Salvinia molesta) has been detected at the old Waihī Beach reservoir. Biosecurity New Zealand is working on this with Western Bay of Plenty District Council, Bay of Plenty Regional Council, AsureQuality, Ngāti Tara Takonui and Te Whānau a Tauwhao.
The reservoir is part of the Western Bay of Plenty District Council stormwater system, and if salvinia spread further it could cause problems for the wider drainage system. To prevent spread, we are asking people to stay out of the waters and to keep pets out of the waters.
Control of Salvinia
Compared with other sites, this infestation is quite large and complex, which means it will be difficult to access and remove all plant material.
We are currently surveying the area to assess the extent of the infestation at this site and in connected waterways. Work will then begin to remove all existing plants, which could take a few months. Manual removal is the preferred method, however careful use of a low-concentration herbicide may be necessary. A fence will be in place while removal is taking place.
Given how serious salvinia is, once all the existing plants are gone there will be a monitoring period for at least two years before this site can be declared free of salvinia.
About Salvinia
Salvinia is not native and can grow rapidly. It can form dense mats that cover entire water bodies, crowd out native plants, increase shade in the water and decrease oxygen levels in the water, affecting the water quality and submerged plants and animals.
Salvinia is a notifiable and unwanted organism under the Biosecurity Act 1993. This means it is illegal to gather or move salvinia.
Salvinia can be spread by water currents, by animals and by contaminated equipment such as kayaks.
For more information about see the Biosecurity New Zealand factsheet about salvinia.
To report suspected salvinia in another location, please call Biosecurity New Zealand on 0800 80 99 66.
