Kānuka could halt kauri dieback disease, study finds

Tuesday, 20 August 2019

With many of Auckland's kauri forests closed to visitors, Stuff takes a look at how rangers are upgrading forest walking tracks to protect our kauri trees.

The cleansing powers of a small native tree could hold the key to helping scientists discover a way to stop the spread of kauri dieback.

Kānuka, a small evergreen, has long been considered by the Ngāpuhi iwi to be a cleansing plant crucial to maintaining healthy forests.

New research now suggests kānuka could actually help halt kauri dieback, in a research paper published on Monday.

Kauri dieback disease has spread rapidly through New Zealand's forests, and last year iwi confirmed it had infected a young tree less than 60 metres from NZ's largest known living kauri tree, T ā ne Mahuta.

**READ MORE:

* This kauri tree-stump has stunned the science world because it refused to die

* Kauri dieback: National treasure on the brink of extinction

* Kauri dieback five-year survey under way: How far has it spread?

Kānuka, a small evergreen native, has long been considered by Ngāpuhi to be a cleansing plant that is crucial to maintaining healthy forests.

* Five years on and diseased kauri injected with phosphite are growing strong**

The disease is 100 per cent fatal to trees and it is spread through soil movement, largely by human visitors to the bush who do not clean their boots properly.

As a result, many walking tracks around the country have been closed.

But scientists have found kānuka's compounds have the ability to halt kauri dieback by paralysing the spores that spread the disease.

'If the spores can't move through the soil, they can't infect kauri, which could spell hope for our forests,' the authors of the paper said.

Numerous walking tracks have been closed in an attempt to stop the spread of kauri dieback.

The pathogen, Phytophthora agathidicida, causes the disease.

Researchers identified four native plants: kānuka, karamū, kawakawa and nīkau that produce anti-Phytophthora compounds. The knowledge used to select these plants descends from Te Whare Wananga o Ngāpuhi.

Extracts of the plants' leaves and roots were tested for their ability to inhibit the disease pathogen.

The research showed the kānuka leaf was the most effective at inhibiting germination and completely eliminating the germination of the pathogen spores.

Overall, the results from the study emphasise the value of using mātauranga Māori in the response to kauri dieback, authors said.

Mātauranga-guided screening of New Zealand native plants reveals flavonoids from kānuka (Kunzea robusta) with anti-Phytophthora activity, was published on Monday.