It was first discovered in a nursery in Kerikeri earlier this month.
A statement today from the Ministry for Primary Industries (MPI) said the riparian plant depot concerned has been closed and is under treatment.
There are four other similar plant depots in Taranaki and movement of plants from these sites has been restricted while investigations continue.
MPI said this means farmers who were intending to collect trees this week will not be able to do so. The regional council is notifying affected parties.
The eight properties affect are: a nursery and adjoining residential property in Kerikeri, two plant nurseries in Waitara, two Taranaki residential gardens, a garden centre in New Plymouth and the regional council plant depot.
MPI said it expects to continue to find new locations of infection given the most likely scenario is that the fungal spores entered New Zealand from Australia during a major wind event.
All infected properties are Restricted Places, meaning there are restrictions on the movement of plants or other risk materials off the sites.
Locations are being treated with fungicide, risk plants are being safely destroyed, and surveillance is underway in the areas surrounding the properties for signs of the disease.
The public is encouraged to report any suspected signs of myrtle rust to MPI's Exotic Pest and Disease Hotline on 0800 80 99 66.
Do not touch the rust or the plant. Note the location and take photos of the symptoms and the plant.