Tuesday, June 25, 2024

Horizon wasps winning wattle battle

A bud-galling wasp introduced by Horizons Regional Council is showing promising signs to deliver on the promise of being a viable control tool against the highly invasive pest plant Sydney golden wattle.

The Council was granted permission by the Environmental Protection Authority to introduce the non-stinging wasp (Trichilogaster acaciaelongifoliae) late last year, after assessing the use of the wasp in South Africa and Portugal against Sydney golden wattle and determining it would not impact native plants.

Horizons environmental manager ,Craig Davey says a recent inspection found the wasps had created galls on Sydney golden wattle growing along our western coastline.

“This was a really exciting discovery because it was the first opportunity for our pest plant team to determine if the release of this friendly, non-stinging wasp has been successful – finding galls means it has,” says Mr Davey.

“The wasp lays its eggs on areas that would become flower buds, which instead produce growths – known as galls – and these prevent flowering and thus seed production. No flowers, no seed, no spread of Sydney golden wattle.

“These galls feed the young wasps, which then emerge as adults for only about three days to lay eggs, thereby creating more galls the following year. The process repeats and the population grows over time.

“Sydney golden wattle, a pest plant that grows well along our coasts, has significant impact on the environment. It suffocates other native species, preventing their growth and creating a mono-culture of Sydney golden wattle.”

He said people 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 is a pest.

Coastal communities were the motivating factor behind securing permission to release the wasp, said Mr Davey.

“These communities have experienced first-hand the devastating impact on dunes, with the wattle covering coastlines from Whanganui to Waikawa.”

“I’d like to thank staff from Manaaki Whenua Landcare Research for their assistance throughout the many years of the project and with inspecting the sites, we are grateful for their help and expertise,” he said.

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