Dutch elm disease has been found on a large Huntingdon elm tree in Auckland Domain.
The fungal disease can spread quickly through a tree and is almost always fatal, Auckland Council said.
Under the Biosecurity Act 1993, it is classified as an unwanted organism and infected trees must be removed to halt further spread of the disease, and to prevent dying trees becoming a hazard.
The tree, located near the band rotunda, is scheduled for removal on January 29.
Auckland Council arboriculture and eco specialist Simon Cook said it was heart-breaking to have the disease confirmed on another of Auckland's iconic trees.
"The disease is arbitrary in nature, making it difficult to eradicate, and as such our programme has focused on ongoing monitoring, followed by identification and removal of any infected elm material," he said.
"There is another elm about 30m away from this infected tree, so we are keeping a close eye on its condition or signs of deterioration."
What is Dutch elm disease?
• It is caused by the fungus Ophiostoma novo-ulmi
• The disease is commonly spread by the elm bark beetle carrying fungal spores from an infected tree to disease-free trees, but can also be spread between trees via root grafting
• Elm wood must not be carried outside Auckland, especially as logs or firewood
• To spot an affected tree, watch for signs of wilting, curling, or yellowing leaves or dying or dead branches and trees
• If you think you've seen an infected tree, contact Auckland Council immediately