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Deadly kauri tree disease found close to Tane Mahuta

28 April 2010

The deadly fungus Phytophthora taxon Agathis (PTA) has been found infecting a kauri tree just 500 metres from Tane Mahuta.

This is the first time that the pathogen has been confirmed in the world-renowned Waipoua Forest, and puts the iconic kauri and other nearby giants at risk of being attacked by the pathogen.

Previously, the closest PTA to Waipoua Forest was found at Trounson Kauri Park in 2005, one kilometre south of the Waipoua boundary.

Landcare Research scientist Stan Bellgard believes that increased efforts are required to ensure Tane Mahuta does not fall victim to the pathogen.

The kauri killing fungus PTA (Phytophthora taxon Agathis) has been found infecting a kauri tree just 500 metres from Tane Mahuta.

Dr Bellgard and his team were shown trees in the Waipoua Forest with classic PTA dieback symptoms by Te Roroa kaumatua Davy Paniora and Stephen King of the Waipoua Forest Trust.

Many of the infected trees discovered to date on Great Barrier Island and near Auckland have been rickers, young regenerating trees up to about 200 years old.

However, at Trounson Kauri Park PTA was recovered from a 2m diameter large tree, at least 600 years old.

Team member Dr Nick Waipara from the Auckland Regional Council said that they had discovered a similar-sized infected tree in a survey at the Cascades Park near Auckland.

The fact that such large trees are becoming infected confirms the possibility that the iconic giants are at risk.

PTA was also found in Raetea Forest to the north of Waipoua, an old kauri logging area planted with kauri in the 1950ís.

Department of Conservation scientist Tony Beauchamp, who has inspected many of the Northland forests for PTA symptoms, says it could have been introduced into this area at the time of planting although further sampling is required to verified this.

Symptoms of the disease caused by PTA include yellowing of foliage, canopy thinning, girdling of the lower branches and the eventual death of the tree.

However, its most distinctive symptom is the excessive bleeding of gum from lesions in the bark near the base of the tree trunk Dr Bellgard says.

Detailed tests have confirmed that one tree with characteristic 'puss-like gummosis' was infected with PTA.  "This is of particular concern because the tree is so close to Tane Mahuta" said Dr Bellgard.

Landcare Research scientists have been working with colleagues at Scion, Plant & Food Research, and the Auckland Regional Council to investigate the threat posed by PTA since it was discovered on the mainland in 2006.

Kauri

Above: The second largest living kauri Te Matua Ngahere located near Tane Mahuta.
Above right: Holdsworth, Alice Mabel, 1878-1963, Agathis australis Kauri. Mr Guy's bush Helensville, May 1937.  Permission of the Alexander Turnbull Library, Wellington, New Zealand, must be obtained before any re-use of this image.
See more on kauri

Project leader Dr Ross Beever says there is still a lot to find out about PTA.  ďIt is a bit of a sleeper, it was first recognised on Great Barrier Island in 1972 but was undoubtedly more widespread even then.

While it is highly pathogenic to kauri, we know very little about how it spreads and infects trees in the wild. We suspect it is exotic, and are investigating it relationships with strains from overseas, especially South East Asia and Queensland.

Present evidence suggests PTA is a soil-borne disease with long-lived resistant spores that can spread by soil movement, and short-lived swimming spores that can be moved in water flow in soil as well as spreading tree to tree through close contact of the roots.

Soil containing the long-lived spores is likely to be transported around on human footwear and by animals such as pigs.

Kauri

Help protect kauri from dieback disease .....

People heading out to enjoy the bush are being asked to do their part to limit the spread of kauri dieback.

Andrew Harrison, kauri dieback long term management programme spokesperson, says ďwe need the publicís help to stop the disease spreading further.  There are simple things people can do".

As a precaution, people should stick to defined tracks in parks and reserves, clean their footwear, tyres and any equipment that comes into contact with soil before and after leaving areas of kauri forest, and avoid disturbing the roots of kauri trees.

Precautions are important for people moving between areas of kauri forest as there are some areas, such as the Coromandel and Hunua Ranges in Auckland, that arenít showing signs of the disease.

Kauri forests are an essential part of New Zealandís ecosystem and home to many other plants and wildlife. Everyone needs to act to prevent the spread of PTA, to prevent the loss of such an iconic species to disease.

The kauri dieback management programme is made up of MAF Biosecurity New Zealand, Department of Conservation, Auckland Regional Council, Northland Regional Council, Environment Bay of Plenty and Environment Waikato.

In October 2009, the Government announced funding of $4.7million into a five year programme to contain the disease, and regional councils involved in the programme have also committed funding which brings total funding for the future management of kauri dieback to $9.8 million.

There are signs up at parks and tracks across the natural range of kauri. More information is available by calling 0800 NZ KAURI, and from the website www.kauridieback.co.nz.

PTA is specific to kauri and can kill trees of all ages. Affected trees show yellowing leaves, canopy thinning, dead branches and lesions that bleed resin across the lower part of the trunk.



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