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.