KEY POINTS:
Most of the great North Island kauri forests were felled to build the villas of colonial New Zealand and post-earthquake San Francisco. Now, an insidious fungus-like disease has emerged which threatens to finish off the remnants of this forest giant.
The only good news is that Biosecurity New
Zealand, the division of Ministry of Agriculture and Forestry charged with guarding the borders from unwanted diseases, has changed its mind about joining the Auckland Regional Council in fighting this threat.
Not that the ARC hasn't done sterling work but this is a national calamity in the making that needs the resources of central government.
Earlier this year, Biosecurity NZ had refused to undertake biosecurity management to mitigate further spread or containment of phytophtora taxon agathis (PTA) because it wasn't a "new organism" as defined by the Hazardous Substances and New Organisms Act 1966.
This was technically true, because PTA had been found on Great Barrier Island in 1972, but at the time it was misdiagnosed as a known species of phytophtora. In April this year Dr Ross Beever of Landcare Research searched the records and found the present killer of kauri in Huia and Cascades in the Waitakare Ranges had never been scientifically identified. However, through DNA technology not available in 1972, he discovered it was also the Great Barrier disease.
To the ARC's credit, it leapt into action by seeking to identify the cause and setting up a management plan to identify the spread of the problem and control its spread.
Credit for sparking off the hunt must go to Dr Peter Maddison, Forest and Bird president and Waitakere Ranges champion, who in 2006 discovered dying kauri in a stand of regenerating trees on the Maungaroa Ridge. He noticed that unlike other phytophtora-related kauri deaths, in this case, all age groups were affected.
Humans and wild pigs have been identified as the two vectors, so signs and shoe-cleaning disinfectant mats have been placed at all entries to the Waitakere park, and eight pig-hunters hired to blitz the ranges.
A pig toxin is also being developed as a permanent solution.
Unfortunately, closing the Waitakere gate is not enough. PTA has also been unearthed in both private and at least three Department of Conservation forests, including Trounson Kauri Park near Waipoua Forest, home of iconic Tane Mahuta.
The worst-affected site is in DOC land at Pakiri, north of Auckland, where 100 trees are dead or dying. How no one seems to have noticed this calamity - or done anything about it - seems incredible.
At this stage, Dr Beever and his team have many questions to answer. Phytophthora is a terrible genus - its translation from the Greek, plant killer, sums it up. It caused the 19th-century potato famine and sudden oak death. Our avocado industry wouldn't exist if every tree wasn't treated each year. It's a grapevine killer as well.
That said, cousins of PTA, thought to have arrived with the first Polynesian settlers, now co-exist in our soils with kauri without the dire results now being experienced.
The samples of PTA, including the Great Barrier one, are all genetically identical, which suggests they come from a single transference, perhaps 50 years ago, perhaps longer.
This begs the question: why has it only now become so deadly? Some are arguing that kauri are delicate at the best of times, and that possibly stress from drought or climate change has now made them more susceptible to PTA. If this is true, and PTA is as widespread as it seems, it is a time bomb that could go off anywhere given the right - for it - conditions.
A fly over of the Hunua regional park and of Kawau by the ARC last week showed no visible signs of outbreak. Nor have two brief surveys on the Coromandel Peninsula. However, a check of the original 1972 Great Barrier site shows a five to 10-fold increase of the disease, with an area of 10ha now affected.
A possible solution is to use a phosphite fungicide similar to that used to protect avocados, but that would involve either regular overhead spraying, or individually injecting each tree. Talk about a nightmare in the making.
