Horizons Regional Council seeking consent to release wasp

Horizons Regional Council, on behalf of the National Biocontrol Collective, have applied to introduce a bud-galling wasp to control the invasive pest plant Acacia longifolia, more commonly called Sydney golden wattle.

This friendly wasp has no bite or sting and has already been through rigorous testing in South Africa and Portugal before the respective countries successfully released the wasp to control Sydney golden wattle.   
Horizons Biodiversity and Biosecurity Manager Craig Davey says he is confident there is sufficient local and international research to indicate the wasp will be successful in New Zealand and not pose a threat to other species. 
“Through testing in Australia we’ve determined the wasp would not impact our native plants,” says Mr Davey. 
“New Zealand native plants are not closely related to the acacia, but those that are similar were assessed in Australia where the wasps remained only on the wattle. Testing in Portugal was an intense process as the wasp was only the second biocontrol agent to be introduced to Europe.
“Horizons has been working on this application since 2018. It’s been a robust, well thought out process, as it is every time we apply to introduce a biocontrol agent, to ensure there are no negative implications.” 
Mr Davey says acacia was introduced to New Zealand as an ornamental plant and had established itself by 1897.
“The pest plant grows well along our coasts and has significant negative impacts on this environment. It suffocates other native species, preventing their growth to create what is known as a mono-culture meaning that only the acacia can thrive.
“Coastal communities have been the motivating factor behind securing the wasp. They’ve experienced first-hand the devastating impacts on dunes with the acacia covering coastlines from Whanganui to Waikawa. Others are likely familiar with the plant, especially in places like Himatangi Beach where the infestation covers most of the dunes, although they may not realise it’s a pest.
“The wasp affects seed production of the wattle, meaning it can’t spread as easily. During the research phase for the wasp we also discovered that a seed-eating weevil was already present in New Zealand. 
“This means we would have two biocontrol agents active, one preventing seed growth and the other eating any seeds that manage to make it through.”
Mr Davey says a biocontrol agent is the best approach to managing acacia effectively.
“Using herbicides and physical control is expensive and can lead to increased fire risk and dune erosion. With plants weakening due to gall (a small crab-apple like ball that grows around the flower bud or stem) production we could see a slower-paced change from acacia dominated dunes to dunes with much more indigenous species being present.
“While we are wanting to introduce the wasp for our coastlines, the acacia infestation is not unique to the Horizons Region and it will be intentionally introduced to other regions.”

If you would like to make a submission on the wasp you can do so here.