The myrtle rust plant disease has shown up at a third site in Northland, bringing the number of infected properties to 17.
The Ministry of Primary Industries said a private garden in Kaikohe had tested positive, after the yellow rust appeared on plants bought from an infected nursery in nearby Kerikeri.
The total number of affected properties nationally now stands at 17 in three regions - Northland, Taranaki and Waikato.
Most of the sites were in Taranaki, where the fungus had affected plants in nurseries, plant retailers and distributors, an orchard and private gardens.
To date myrtle rust has been found on pōhutukawa, lophomyrtus, gum trees and a single instance of mānuka - but not yet on feijoa trees.