Stopping kauri dieback in its tracks

  • Kauri canopy.

    Kauri canopy.

  • Kauri cone. Image - Vicky Forgie

    Kauri cone. Image - Vicky Forgie

  • Kauri gummosis.

    Kauri gummosis.

Project 2.7

Leader: Dr Monica Gerth, University of Otago

‘A biosecurity team of 4.7 million’ is the first of five strategic direction statements in the draft Biosecurity 2025 Direction Statement for New Zealand.

The National Science Challenge for NZ’s Biological Heritage is funding two new programmes, including this one, to enlist the public’s help in dealing with the very worrying disease killing our kauri trees.

Summary

This project, led by Dr. Monica Gerth at the University of Otago, will use a combination of biochemistry and mātauranga Māori to try to foil the spread of kauri dieback. Kauri dieback is a fungus-like disease (Phytophthoraagathidicida) that is causing the decline and death of thousands of kauri. Phytophthora pathogens are problematic worldwide.  Another host-specific form (P. infestans) caused the Irish potato famine, and one with a more general appetite is attacking many Australian natives and avocado trees (P. cinnamomi).

A major way kauri dieback disease spreads is by free swimming zoospores in soil.  With their long flagella and rudders, these spores can swim through water-logged soil at amazing speeds of up to 0.7 metres per hour.  Once they find their target kauri roots, they encyst and initiate an infection that eventually starves the tree to death.

The question at the heart of their research is:  what is it about kauri roots that attracts the zoospores? These spores seem to find the smell of kauri as alluring as coffee is to humans. Dr Gerth and her team will identify the chemical signals from kauri and other native plants that attract, repel or generally disrupt the 'homing' ability of zoospores - and then, in collaboration with Dr. Amanda Black (Lincoln University), they will test the effect of these compounds on the movement of zoospores through soils.

The overall goal of their research is to provide new tools to protect New Zealand's kauri forests. For instance, zoospore repellents could potentially be applied around kauri trees to deter the spores. Long term, the general principles of their research may also be applied to the battle against other plant pathogens.

Understanding the interactions between P. agathidicida and its host plant kauri is an essential step in developing disease control strategies. The overall goal of this research is to prevent P. agathidicida from spreading to uninfected trees. Our hypothesis is that infection can be prevented by interfering with the chemotactic responses of this pathogen. Some Phytophthora species, such as the pine pathogen P. pluvialis, produce airborne spores that infect leaves. In contrast, P. agathidicida and other root rot Phytophthora use motile zoospores to infect the roots of their hosts. Phytophthora zoospores can travel great distances in waterlogged soil, and once they have located a host’s root, they encyst on the surface to initiate infection. Although chemotaxis is clearly an important part of Phytophthora pathogenesis (and a prerequisite for infection by some species), this behaviour in P. agathidicida remains almost completely uncharacterised. Here, we will investigate critical aspects of P. agathidicida chemotaxis and how this contributes to its movement through landscapes.

Mātauranga Māori offers important insights for this research, as native plants are almost certainly important sources of naturally occurring chemo-attractants or repellents. As part of our proposed project, we will seek to build research collaborations with kaitiaki and other experts in ngahere kauri, building on Dr. Amanda Black's strong connections to Iwi, kaitiaki and Māori researchers, and the Kauri Dieback Programme Tāngata Whenua Rōpū. This will also help us to ensure that any treatment or methodology is compatible with tikanga. As a first step, we have undertaken a formal consultation with our local Iwi, Ngāi Tahu, via their Research Consultation Committee. The Ngāi Tahu Committee supports our proposed research, noting that it is “of interest and importance” and that “any work to aid in its [i.e. kauri’s] health and proliferation is very important”. Our next steps will be to liaise with Far North Iwi and hapū to develop more of a research partnership approach based on sites suggested by them.

Overall, successful implementation of our research has the potential to prevent the spread of kauri dieback, and stop the loss of these culturally and environmentally important trees. These benefits are encapsulated both within the Challenge Mission and the Vision Mātauranga Taiao (environmental sustainability) theme.

Keep Kauri Standing

The collaborative effort to address kauri dieback includes the Ministry for Primary Industries, the Department of Conservation, Auckland Council, Northland Regional Council, Waikato Regional Council, Bay of Plenty Regional Council and Tāngata Whenua. We are working together as one team to ensure the integrity of kauri ecosystems remains, to protect high value kauri areas and iconic kauri trees.

Kauri Dieback Recreation Project

This project is DOC's on the ground response to the disease killing kauri trees in the North Island. It aims to control the human spread of kauri dieback on public conservation land.

What is Kauri Dieback Disease

Alison Ballance, Our Changing World, 16 May 2013

Several years ago a new plant disease was identified in New Zealand – Phytophthora taxon Agathis, also known as PTA, or kauri dieback disease, which infects and kills giant native kauri trees (Agathis australis). The effects of kauri dieback disease were first noticed 40 years ago in a stand of trees on Great Barrier Island, but the organism was wrongly identified as another species of Phytophthora and it wasn’t until the mid-2000s that the late Ross Beever realised that organism was actually PTA. There is no cure and no vaccination for PTA, which is found only in New Zealand and infects only kauri trees.

What's new

Kauri dieback zoospores
How kauri dieback spreads between trees

20 June 2017 - Whats new

A University of Otago team have captured amazing video of how kauri dieback zoospores swim through wet soil…

Kauri gummosis. Image - Richard Gordon
Kauri dieback and how microbes sense the world

7 June 2017 - Whats new

Alison Ballance talks to Monica Gerth about her research using a combination of biochemistry and mātauranga Māori to…

Dr Mels Barton, left, and Dr Marie McEntee are conducting a public survey on kauri dieback disease as part of Kauri Recue. Image - Simon Smith, Fairfax NZ
New research to work out how to help kauri

10 January 2017 - Whats new

Simon Smith reports on two new studies, funded by the National Science Challenge for New Zealand's Biological Heritage,…

Kauri dieback desease. Image - NZ Herald
Why is killer disease drawn to our kauri?

10 January 2017 - Whats new

Scientists are seeking to solve one of the most intriguing mysteries of the disease that's killing our kauri…

Radio-collared rat. Image - Andrea Byrom
Research funding announcement

20 December 2016 - Whats new

The National Science Challenge for NZ’s Biological Heritage has approved six new research projects from its latest contestable…