He aha te mana koiora?
What is biocontrol?
Pest plant biocontrol is the act of introducing a natural enemy to control a pest plant. These natural enemies are either insects or pathogens. Once released in a new region, they are referred to as ‘biocontrol agents’.
Biocontrol agents controlling pest plants in Tāmaki Makaurau / Auckland
Many biocontrol agents have been successful at controlling their host plants in Tāmaki Makaurau / Auckland. For example, ragwort used to be widespread across the region. The introduction of the ragwort flea beetle led to a huge reduction in ragwort across the region. A result manual control alone could not achieve at that scale.
Other biocontrol agents also active in the region, include;
mistflower rust fungus
tradescantia yellow leaf spot fungus
tradescantia leaf beetle
Biocontrol is a long-term method, not a quick fix. Here's what to expect:
Years 1–2: Insect or pathogen establishes at the release site
Years 3–5: Populations grow, damage to pest plant becomes visible
Years 5+: Pest plant becomes easier to manage alongside other method
Biocontrol benefits
Long-term sustained control of the pest plant to low densities.
Native flora regeneration and improved biodiversity at site.
Cost-effectiveness.
Reduced reliance on herbicides.
Overall reduction in the dominance and impacts of widespread pest plants in the region.
Biocontrol safety
Each potential biocontrol agent is subject to years of testing to ensure it is safe to release. This includes examining whether it will feed on desirable plants or have any negative interactions with other native insects or birds. The Environmental Protection Authority (EPA) must approve every release, through a process that includes public consultation, iwi engagement and consideration of mātauranga Māori.
See the EPA website for information about the process of safely bringing a biocontrol agent into Aotearoa.
Auckland Council also carries out engagement with mana whenua across the region on biocontrol and you can find a report on Knowledge Auckland.
If you find a biocontrol site don't disturb it
Always look for biocontrol signage before starting any pest control work (herbicide or manual). If biocontrol is in place at a site, it’s essential to leave that site uncontrolled with other methods (herbicide or manual). This is the most important thing the public can do.
If biocontrol is happening at a site:
don't spray
don’t pull weeds or remove any parts of the pest plant
Removing the pest plant removes the food source for the beetles or other biocontrol agents causing them to die off. Other types of disturbance can reduce the biocontrol agent’s ability to control the pest plant. If you're a community group working on public land and you're not sure, contact us first: pestfree@aucklandcouncil.govt.nz
Find biocontrol 'no go' sites
You can find the current biocontrol 'no go' sites on the Auckland Council GeoMap.
Instructions:
Click on the 'Switch themes' button in the top blue tool bar of the map (hover over each icon to see what they are called).
Select 'Environment' - the left-hand side panel will change and the 'Legend' tab will list headings for the various layers.
Click the down arrow for 'Natural Environment Conservation'.
Select 'Biocontrol Release Zones' - these will show in red on the map.
