A newly identified disease killing kauri trees in the Waitakere Ranges is threatening to devastate the population in the Auckland region.
The kauri collar rot is caused by a soil pathogen known as Phytophthora Taxon Agathis, and kills trees of all ages and sizes.
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.
Nick Waipara from Auckland Regional Council the council, who helped identify the disease, says it could devastate the Kauri population as it is too widespread to eradicate.
Dr Waipara says people can help prevent its spread by washing shoes, and sticking to walking tracks when in the Waitakere Ranges or on Great Barrier Island.
Diseased kauri trees were first discovered along the Maungaroa Ridge near Piha in 2006, but it was not known what was causing the symptoms until April this year, following intensive research.
Scientist are assuming the pathogen is exotic, possibly tropical in origin, however nothing is known about this species worldwide.