The Environmental Protection Authority (EPA) has approved a rust fungus and a flower weevil to control Darwin’s barberry, a spiny invasive shrub.

Environment Canterbury, on behalf of the National Biocontrol Collective, applied to use two biological control agents to combat Darwin’s Barberry ( Berberis darwinii) in New Zealand. Those biocontrol agents are a rust fungus ( Puccinia berberidis-darwinii) and the Darwin’s barberry flower weevil ( Anthonomus kuscheli).

Darwin’s barberry is a resilient noxious weed found in disturbed forests, pastures, shrubland and short tussock-land. It is a threat to indigenous ecosystems throughout the country, as well as to pastures where livestock graze. Standard control methods such as herbicides or weeding are often costly, impractical and harmful to the environment.

It is native to Chile and Argentina and was introduced to Aotearoa New Zealand as a garden plant in the 1940s. Fruit-eating birds deposit seeds far from the parent bush, increasing its spread.

The plant can be found throughout New Zealand - particularly in the Canterbury, Otago, and Wellington regions. These biocontrol agents could also be used to target Darwin’s barberry elsewhere in the country.

Both the flower weevil and the rust fungus proposed for introduction are native to South America. All organisms new to New Zealand must receive approval from the EPA before being released into the New Zealand environment.

"The independent decision-making committee approved the introduction of these two organisms following a rigorous, evidence-based assessment," says Dr Chris Hill, General Manager of Hazardous Substances and New Organisms at the EPA.

"The applicant’s risk assessment showed that these agents are highly unlikely to harm native plants or animals. The weevil does not bite or sting, so there is no health risk to people, and the rust fungus is also benign."

Dr Hill says the decision followed public consultation, engagement with mana whenua, and consideration of international best practice.

"New Zealand has a strong track record of using biological control agents to manage invasive weeds with minimal impact on native ecosystems," he says.

In recent years the EPA has approved other biocontrol agents for weeds such as purple loosestrife, old man’s beard, Sydney golden wattle and moth plant.

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