Biocontrols in NZ

New Zealand has a 90 year history of working with insect and pathogen (rusts/blights) biocontrol agents. So far, 59 biological control agents have been released against 22 target species. There has been no significant non-target attacks in New Zealand.

Some biological control agents have been enormously effective in New Zealand. Many Northlanders will recall the fields of yellow ragwort that were once a common sight. In the late 1980’s and 1990’s the ragwort flea beetle was widely distributed and is responsible for the decline of ragwort in New Zealand. The current saving to just the dairy industry in herbicide expenditure (without taking into account equipment or labour) for ragwort, is $44 million annually. In the 1920’s New Zealand had the opportunity to bring in ragwort flea beetle but turned it down – this is estimated to have cost the country $8.6 billion in lost production over the past 90 years.

Recently biocontrol agents have been released in New Zealand for tradescantia, woolly nightshade, Chinese privet and Japanese honeysuckle.
Biocontrols are a safe and effective management tool – there have been around 550 agents released worldwide against 224 weed species with only 8 instances of non-target attack and 7 of those were predicted. Scientists can predict what biocontrols will attack because of something called ‘host-specificity’. Related plants use the same chemicals for defence, so most insects can only attack closely related plants that they have evolved to feed on.


Landcare Research are funded by the National Biocontrol Collective (10 regional councils, 3 unitary authorities and the Department of Conservation) to investigate biological controls on behalf of New Zealand. They have been working with the Centre for Agriculture and Biosciences International, a UK-based research organisation in Nepal to identify the best prospects for import into New Zealand.

Unfortunately because of India’s strict export controls and lack of funding, these biological controls have not been researched enough for import and India will not as yet allow their export.

We need assistance at diplomatic levels and increased funding to make sure these biocontrols are suitable for New Zealand.

Each species costs around $50,000 a year initially to research, with costs increasing if they are successfully imported and mass-reared and then declining as the programme turns to monitoring their spread and no longer importing new insects.

$400,000 a year would cover the cost of research, host-testing, mass-rearing, import and bureaucratic support. Wild Ginger is already estimated to cost Northland close to $3 million annually. Wild Ginger could cost our economy even greater amounts in the future if we lose our valuable native forests.

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