Northland's iconic 2000-year-old kauri Tane Mahuta is under threat.
A kauri-killing fungus has been found just 500m away from the Lord of Waipoua Forest.
Stephen King, from the Waipoua Forest Trust, said the fungus - Phytophthora taxon agathis (PTA) or kauri dieback disease as it is also known - was a serious
threat to Tane Mahuta and the other giants in Waipoua Forest.
Mr King said Tane Mahuta and the other giant kauri in Waipoua were national icons and urgent action was needed to protect them.
That would include putting up boardwalks around the trees, starting trial treatment methods on the infected trees and dealing with the wild pig problem in the forest.
Landcare Research scientist Stan Bellgard, who was part of the team that discovered the fungus in the Waipoua kauri after being guided into the forest by Te Roroa kaumatua Davy Paniora and Mr King, said the fungus was a soil-based pathogen and would be spread by people or animals disturbing the kauri roots.
"PTA has come from overseas and is almost identical to a Taiwanese [fungus] in molecular structure, but looks different," Dr Bellgard said.
"We now have to find out how widespread it is in Waipoua and it's up to the authorities to decide what to do about it."
Of major concern for Dr Bellgard was that the latest infection was on a more mature tree. Increased efforts are required to ensure Tane Mahuta does not fall victim to the pathogen.
"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," Dr Bellgard said.
"That's a major concern."
DoC conservation support manager for Northland, Hilary Aikman, said the Kauri Dieback Response Team, which was made up of DoC, MAF Biosecurity NZ and regional councils from the upper North Island, took the threat seriously.
Work was progressing on walking tracks around the iconic Waipoua kauri to prevent people spreading the disease, she said.
Toxicology work was also being carried out to determine methods of treatment.
Te Roroa spokesman Alex Nathan said the iwi was in regular contact with the scientists involved in the find.
