Help us combat Darwin’s barberry using biological controls
We invite you to share your views on our joint application to introduce two biological control agents to manage Darwin’s barberry (Berberis darwinii), an invasive woody shrub.
We applied, on behalf of the National Biocontrol Collective, to introduce Darwin’s barberry flower weevil (Anthonomus kuscheli) and Darwin’s barberry rust fungus (Puccinia berberidis-darwinii) to target this unwanted shrub in late February. If approved, these agents could also target Darwin’s barberry across New Zealand.
The National Biocontrol Collective is a collaboration between Regional Councils, Manaaki Whenua Landcare Research, Department of Conservation and Ministry for Primary Industries.
Any organisms new to New Zealand must receive approval from the Environmental Protection Authority (EPA) as the national environmental regulator.
Identifying Darwin’s barberry
Darwin’s barberry is an invasive, spiny shrub found in forests, scrublands, and degraded pastures. It has:
- tough, woody stems with sharp spines and glossy, dark green, spiny-edged leaves
- golden-yellow flowers (July–February) in clusters and oval, purple-black berries
- it spreads rapidly as birds and possums disperse its abundant seeds.
- dense infestations outcompete native seedlings, altering the understorey.
The species is widespread in Waitaha/Canterbury, with over 250 known sites covering 2,500 hectares.
Find out more about this invasive weed: Darwin’s barberry.
Darwin’s barberry
What is biological control?
Biological control is the use of one living organism to control another. The organism that undertakes the control is called the ‘biological control agent’ or ‘biocontrol agent’ with the target species called ‘the host’. In weed control, this is often an insect or a fungus.
Most plants introduced into New Zealand do not have the same natural enemies that they have at home. This means they can flourish here, as there is nothing to naturally keep them under control. Over time they can spread into the natural environment, affecting biodiversity, economic, cultural, and recreational values.
Benefits of biological control
- Once established, biocontrol is inexpensive compared to other control methods.
- Some weed populations can’t be suppressed effectively by other methods. They can re-sprout after herbicide application, or they become resistant to herbicides over time. Biocontrol agents, however, adjust in response to weed populations.
- Biocontrol agents can be used in inaccessible areas where it’s unsafe or expensive for manual or chemical control to occur.
- Biocontrol agents are safer for non-target species than herbicides or other agrichemicals.
- They can be introduced into sensitive habitats near waterways or areas with important flora and fauna.
Selection process for biocontrol agents
Biocontrol agents are extremely specific to their host and rigorous testing is undertaken to ensure they won’t affect non-target species like native plants and crops or become pests themselves.
Selecting a new biocontrol agent is a long and thorough process, often taking between 5–10 years of research before an application is submitted to the EPA - longer in extreme cases.
Proposed biocontrol agents for Darwin’s barberry
The two proposed biocontrols are:
- Darwin’s barberry flower bud weevil (Anthonomus kuscheli)
- Darwin’s barberry seed weevil (Berberidicola exaratus).
Both agents have been rigorously tested with little to no negative impact on our native ecosystem.
Successful biocontrol in Waitaha/Canterbury
Many biocontrol agents have been successful at controlling their host plants in Canterbury including:
- Green thistle beetle (Cassida rubiginosa) for Californian thistle.
- Broom gall mite (Aceria genistae) for Scotch broom and white broom.
- Uromyces pencanus rust fungus - recently approved fungal tackling the highly invasive Chilean needle grass.
- Tradescantia yellow leaf fungus released in Christchurch and Kaikōura to help control tradescantia, an invasive creeping weed also known as wandering willie.
Help shape our efforts against Darwin’s barberry!
If you care about tackling Darwin’s barberry and support our proposed approach, we’d love to hear from you – make a submission to the EPA.
Submitters can provide information, make comments, and raise issues to contribute to the EPA decision-making process.
If you have any questions relating to the application process, please contact the EPA.
Submissions close at 5.00pm on 22 April 2025.