Manawatū and Whanganui could soon be home to a new foreign wasp.
The bud-galling wasp (Trichilogaster acaciaelongifoliae) has been shown to help prevent the seed production of Sydney golden wattle. Photo: CBG Photography Group, Centre for Biodiversity Genomics
On behalf of the National Biocontrol Collective - a consortium of regional councils, unitary authorities and the Department of Conservation - Horizons Regional Council has applied to import and release the bud-galling wasp to control the spread of an invasive acacia shrub.
Biosecurity and biodiversity manager Craig Davey told Morning Report the insect had been shown to stop most seed production of the plant.
"It is only existing to live on Sydney golden wattle. So when we release it, if the application is successful, it's only going to live on those acacia that are in our coastline."
"It spends about 360 days inside the plant, and only flies around about three days of its life" - Horizons Regional Council biosecurity and biodiversity manager Craig Davey
Since it was introduced, the Sydney golden wattle has become widespread throughout coastal areas of the North Island, and is considered a threat to biodiversity and to the conservation of dune and other ecosystems.
While the wasps would not remove the plant, stopping the spread of Sydney golden wattle was essential because it invaded native plant communities and was a fire risk, Davey said.
"Up in Northland, the fires that occurred up there, triggered and supported and accelerated by the huge infestation of Sydney golden wattle," he said.
"Because it's a good dune stabiliser, it layers so it creates stems that can be rooted, so it doesn't just rely on the original plant. It gets bigger and bigger and bigger, so the dunes get huge and then can create sand blows.
"Another bad thing is it's an allergen, so people get really bad hay fever symptoms from it as well."
The wasp, which spent most of its life inside the plant and only about three days outside, laid its eggs in the flower buds, which prevented flowers forming and seed production, he said.
"It's perfectly tuned for this plant and so when a flower tries to grow, it can't, because the wasp has an egg that means a plant puts all its energy into stopping this insect, so the plant ends up not producing seeds."
The wasps do not bite or sting, and there are no native New Zealand insects that are closely related.
"You're going to be lucky to see it, it's only about 3 millimetres in size. It's quite cool, it's brown with a big red head, red eyes," Davey said.
The Environmental Protection Authority, which is considering the application, is asking for submissions to be made before midnight on 30 September, 2022.