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 (All regional authorities in New Zealand and the Department of Conservation) to investigate biocontrols on behalf of New Zealand. They have been working with CABI (Centre for Agriculture and Biosciences International), a UK-based research organisation who sends scientists to Nepal to identify the most appropriate species for import to New Zealand. Due to lack of previous funding, these biological controls have not yet been researched enough for import into New Zealand and India’s strict export requirements may also prevent agents from reaching New Zealand.

Each species costs around $50,000 annually to research, with costs increasing as agents are imported and mass-reared for release in special quarantine laboratories, and then declining as the programme shifts towards monitoring their spread and impact. 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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