Feasibility of biocontrol for purple loosestrife
Feasibility of biocontrol for purple loosestrife
Lythrum salicaria (Purple loosestrife) is a noxious weed in North America and Canada and is naturalised in New Zealand, South Africa, Chile and Argentina.
Scattered and isolated populations are known in the Auckland, Taranaki, Bay of Plenty, Wellington, West Coast and Marlborough regions where it is targeted for eradication. In the Canterbury and Manawatu-Whanganui (Horizons) regions fully naturalised populations of L. salicaria occur.
L. salicaria has the ability to invade lakesides, riparian zones, wetlands, roadside ditches and pasture. Once established, L. salicaria can expand rapidly forming dense stands and displacing wetland and riparian flora and at high densities transform ecosystems. Conventional control methods are generally unsuccessful in the long term and require a high amount of effort and cost. Options for control are also limited due to the sensitivity of the wetland and riparian habitats where the plant is generally found.
Lythrum salicaria in flower growing along a lake. (Credit: Trevor James)
To explore other options for control of L. salicaria, Horizons Regional Council secured an Envirolink grant and contracted Manaaki Whenua - Landcare Research to investigate the prospect of developing a biocontrol programme for the plant in New Zealand.
The work focused on the following three areas:
- A review of relevant literature and identification of potential biocontrol agents for salicaria and assess their feasibility for release in New Zealand;
- Assessment of the prospects of achieving successful biocontrol of salicaria;
- Estimation and an outline of the cost of implementing a biocontrol programme for salicaria in New Zealand.
The report also provides key steps to implementing a biocontrol programme for L. salicaria and what work and process would be required.
Craig Davey, Biodiversity and Biosecurity Manager for Horizons said the work has been valuable at a regional as well as national perspective. He says “We’ve used the work as reference material to create plain English documents to present across the country for use by both ourselves and other regional councils and organisations”. Craig also spoke of the opportunity that Biocontrol can provide as an option to help control L. salicaria without needing to use other methods leading to effective use of resources. When asked what the most important outcome of the work has been Craig said “this work has provided us with the confidence to go out and have a robust conversation with the public on the biocontrol options”.
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