Origin and current locations

Where did it come from?

Spores of kauri dieback were first discovered along with sick kauri on Great Barrier Island in the 1970's.  Identification methods at the time led to these samples being misclassified as a morphologically similar species.

Kauri dieback was formally identified in April 2008. Its closest known relative is a chestnut pathogen from Taiwan (Phytophthora katsurae).

It's origin and time of arrival in New Zealand is still unknown, but evidence suggests it was introduced from overseas. This assumption is currently based on the narrow genetic variation found in the disease population (indicating a relatively recent introduction that hasn't had time to evolve variation) and the preference for high soil temperatures which suggests a more tropical origin.

Kauri dieback growth rate in agar culture, at various temperatures.
Dr Ian Horner, May 2007
graph
Mycelial growth rate, averaged across eight different kauri dieback isolates.

Is kauri dieback really a 'new disease to science'?

Spores of kauri dieback were first discovered from the soil underneath sick kauri and in soil near seemingly "healthy" kauri on Great Barrier Island in the 1970's.  Identification methods at the time led to these samples being misclassified as a morphologically similar species and known kauri associate Phytopthora hevae considered to pose a low risk to kauri.

Kauri dieback was formally identified by Landcare Research work in April 2008 following reports of kauri tree death in the Waitakere Ranges. Laboratory investigations found kauri can be very susceptible to this disease, with seedlings dying within weeks of infection.

So although kauri dieback has been in New Zealand for at least 40 years, it was not correctly identified as a 'new species to science' or understood to threaten kauri ecosystems until 2008.

NB. Spores recovered from soil around healthy trees does not necessarily indicate that those trees are not or will not be affected by the disease. This may indicate a lag phase (period of time between the introduction to an area of soil and the activity/infection of the tree) or early infection at root level.

There is a small chance, that a degree of tolerance or resistance to the disease may also explain such findings.

 

Where is it?

Kauri dieback has been found in the Waitakere Ranges Regional Park, on private land throughout the Auckland region, in the forest plantations of Omahuta, Glenbervie and Russel in Northland, Department of Conservation reserves at Okura, Albany, Pakiri, Great Barrier, Trounson Kauri Park and Waipoua Forest in Northland, home of our most iconic kauri - Tane Mahuta.

In March 2014, kauri dieback was also unfortunately found in bush in the Coromandel Peninsula - work is underway to determine the extent of this infection.

At this stage, the disease has not been detected in many areas of Northland forest, the Hunua Ranges and Hauraki Gulf Islands (excluding Great Barrier). It's imperative that we protect these uninfected areas.

Download map to view locations.

A national surveillance programme is underway to determine the distribution of kauri dieback in New Zealand. Knowing which forests are still healthy and which are contaminated is critical to ground management.  As kauri dieback spores are microscopic and invisible to the naked eye, our surveillance programme often depends on reliable detection and diagnostic methods to confirm if soil or plant samples are PTA positive.  A collaborative partnership between our programme and Landcare Research, Scion Research and Plant & Food Research have successfully developed a standard method to bait PTA out of soil into pure culture and then genetically sequence each isolate to confirm the identity of each cultures as being PTA.  Using the genetic sequences of PTA, a direct DNA probe is also under development which may allow for the faster detection in the field.