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ARC tackles new Kauri tree disease

ARC tackles new Kauri tree disease

11 July 2008

The Auckland Regional Council is tackling a newly identified disease attacking kauri trees in the Waitakere Ranges.

The disease is a kauri collar rot, caused by a soil pathogen known as Phytophthora Taxon Agathis (PTA). It causes a progressive collar rot that can girdle the tree and eventually kill it. Affected trees show yellowing leaves, canopy thinning and dead branches and they can develop lesions that bleed resin across the lower part of the trunk.

Diseased kauri trees were first discovered along the Maungaroa Ridge near Piha in 2006, but it was not known what was causing the symptoms. Extensive research has been done since and it was confirmed in April this year as a kauri collar rot caused by PTA.

Until then it had not been identified as a new species, nor was it known that PTA caused kauri to die, but this was confirmed by research led by Dr Ross Beever from Landcare Research and assisted by Dr Nick Waipara from ARC.

“We are very concerned and will be doing everything we can to control the spread of the disease,” says Cr Sandra Coney, Chair of ARC’s Parks and Heritage Committee.

“The ARC owns the largest area of kauri forest in the Auckland region, most of it regenerating from milling 100 years ago. We are putting in place preventive measures to stop the spread of the disease and we need research to understand how widespread it is in the Ranges.”
“We need the public to help stop this disease from spreading within the Ranges and further afield, and to tell us if they notice sick trees.”

“PTA is a pathogen that attacks specifically kauri and it’s essential that we do more research into where it is, what its vectors are for spread and how to stop it,” says Dr Waipara of ARC Biosecurity.

“We do know that it is a threat to kauri at ecosystem level as well as individual trees and that it is soil-borne, which means we can act now to prevent further spread.”

“A likely vector for spread is feral pigs, and we will be making a concerted effort to reduce pig numbers significantly in the Ranges” says Dr Waipara.

“Pig control is something the ARC can action very quickly.”

The ARC is also rolling out standard operating procedures to their own staff and to contractors working in the Waitakere Ranges as well as communicating with all the relevant organisations and local communities that use the Ranges regularly and for one-off events.

Measures will be similar to those for biosecurity risks like didymo in the South Island and will include things like disinfectant footwear mats for events and information for the public who will be asked to clean their shoes before entering and after leaving the Ranges.

Councillors will consider allocating research funding at the next Parks and Heritage Committee meeting.


Notes for editors:

Kauri collar rot disease has been observed in the ARC Cascades Park by Dr Nick Waipara (ARC Biosecurity) and Dr Ross Beever (Landcare Research).

• The disease is caused by a pathogen, currently known as PTA (Phytophthora Taxon Agathis). Until April 2008 it had not been identified as a new species, nor was it known that PTA caused kauri mortality.

• Symptoms include yellowing of foliage, canopy thinning, appearance of dead branches and tree death. Affected trees can also develop lesions that bleed resin.

• A Phytophthora disease was first identified in the Waitakere Ranges in 2006 and observations are similar to those from Great Barrier Island in the 1970s.

• PTA has also been isolated from soil in Waipoua Kauri Sanctuary, Northland

• PTA is a soil borne species – spread by soil and soil water movement, plant to plant transmission through underground root-to-root contact, water movement, human and animal vectors.

• It kills trees of all ages and sizes.

• Kauri dieback caused by a Phytophthora was first discovered on Great Barrier Island in the 1970s.

• Its closest known relative is a chestnut pathogen from Korea (Phytophthora katsurae)

• The assumption is it’s an exotic pathogen, possibly tropical in origin, however nothing is known about this species worldwide.

• PTA isn’t listed as Unwanted Organism under Biosecurity Act 1993 as it would not be regarded as a new organism under the Hazardous Substances and New Organisms Act 1996 (HSNO) because it is now known to have been present in New Zealand prior to 29 July 1998.

• There are significant information gaps about the disease, its vectors and management options. Although kauri damage has only recently been discovered, the disease may have been in the Ranges for many years, as symptoms may take years to become apparent.

• More research is needed urgently into the biology, pathology and management of PTA and the extent of PTA in the Waitakere Ranges, its vectors of spread and possible control methods. ARC is looking at co-funding this initial research until national funding can be obtained, or even underwriting this research if other funding partners cannot be found.

Management options:

• Eradication is unlikely to be achievable due to the extent and widespread nature of the pathogen and time since it was first recorded. The disease may have been here for many years.

• Containment options can be considered for some affected areas but we urgently need more survey information to determine the extent of distribution.

• Protection of PTA-free areas is possible through exclusion of vectors (closing tracks, restricting access, disinfection of equipment), however water and feral pig movement may be more significant vectors.

• Control through tree injection or foliar spray is an option, as related Phytophthora diseases are effectively managed in NZ and Australia.

• Common phosphate-based fungicides are not known to be effective against PTA, we would need to know more about safe application rates.

• Education/public awareness Information for the public is being developed by the ARC

• A Standard Operating Procedure for ARC staff and contractors working in affected areas is currently being rolled out.

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