Options for control of Vallisneria spp. include mechanical removal, (with weed harvesters or suction dredges), chemical control with herbicide, manipulation of the habitat by drainage or weed mats and biological control with agents such as grass carp (Environment B.O.P. Undated). However, biological control should be carefully considered in respect to all situation-specific biotic variables. Taking biological control out of context, especially when there is a lack of robust scientific data, might cause more damage to an ecosystem than it prevents. Froude (2002) notes that while some generalist herbivorous fish promoted as biocontrol agents will reduce the biomass of plants in an area, their browsing is not host-specific as they reduce both undesirable and favoured plants. As an example she mentions grass carp used to reduce aquatic plant biomass.
Location Specific Management Information
Auckland Region (North Island)
Vallisneria spiralis is designated as a Total Control and Surveillance Pest by the Auckland Regional Pest Management Pest Management Strategy 2002-2007.
Bay of Plenty Region (North Island)
Under the Environment Bay Of Plenty’s Plant Pest Management Strategy, plant pests, including aquatic plant pests, have been categorised according to the type and level of intervention that will be undertaken. The strategy was developed by assessment of the weediness of each plant and after consultation with the public and Government agencies. Eelgrass (Vallisneria gigantea (Vallisneria nana), V. spiralis) have been classified as a “Regional Surveillance Plant Pest”, a category that includes species that were formerly present in the region but have now been largely eradicated. Continued surveillance of former sites is required. Any new sites will be investigated and control carried out by Environment B•O•P.
Environment B•O•P Plant Pest Officers are available to help identify and advise on appropriate control measures for Aquatic Plant Pests. Vallisneria is banned from sale, propagation and distribution (Environment B.O.P. Undated).
Canterbury Region (South Island)
Vallisneria spp. is designated as an "Unwanted Organism" and is banned from sale, propagation and distribution throughout New Zealand. Please see the Pest management strategy Part II 3.1 for defintions of classification of pests.
Vallisneria spiralis is listed on the MAF Biosecurity Index with information on importation status/standards. All Vallisneria spp. (V. asiatica, V. americana, V. americana var. biwaensis and V. torta) are probably treated as one species by MAF (following Healy & Edgar 1980). It is a plant pest under the Biosecurity Act 1993 and is controlled under Plant Pest Management Strategy (PPMS). It is listed on the Landcare database of vascular plant species present in New Zealand (Champion & Clayton 2001).
Wellington Region (North Island)
Eelgrass Vallisneria spp. (except twisted leaf variety) is targeted as a plant pest for eradication. The public may inform the regional council of infestations on their property and they will be eradicated no cost. The long term objective is to eradicate this relatively rare pest plants from the region. It is also illegal to sell, propagate, or distribute any parts of these eradication pest plants in the Greater Wellington region (Greater Wellington Regional Council 2004c).
West Coast Region (NZ) (South Island)
Vallisneria is classified as a “Potential Plant Pest” by Environment Waikato, which means it is recognised as a potentially invasive weed in the Waikato Region.
3. Champion, P.D.; Clayton, J.S. 2001. Border control for potential aquatic weeds. Stage 2. Weed risk assessment. Science for Conservation 185. 30 p.
Summary: This report is the second stage in the development of a Border Control Programme for aquatic plants that have the potential to become ecological weeds in New Zealand. Importers and traders in aquatic plants were surveyed to identify the plant species known or likely to be present in New Zealand. The Aquatic Plant Weed Risk Assessment Model was used to help assess the level of risk posed by these species. The report presents evidence of the various entry pathways and considers the impact that new invasive aquatic weed species may have on vulnerable native aquatic species and communities.
Available from: http://www.doc.govt.nz/upload/documents/science-and-technical/SFC185.pdf [Accessed 13 June 2007]
4. Environment Bay of Plenty. Undated. Part 2: Plant Pest Management Programmes. Environment B.O.P. (Bay of Plenty Regional Council): Bay of Plenty.
6. Greater Wellington Regional Council. 2004a. Eradication Pest Plants.
7. Greater Wellington Regional Council. 2004b. Eelgrass. [Accessed 9 February 2005, from ]
8. Greater Wellington Regional Council. 2004c. Help Stop Aquatic Alien Invasion. [Accessed 9 February 2005, from: ]
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