The fungal plant disease myrtle rust has now been confirmed in King Country after earlier finds in Northland and Taranaki.
The disease was identified in a small number of plants at a nursery in Te Kuiti after Ministry for Primary Industries officials tracked the sale of plants from another nursery, it said on Tuesday.
Restrictions have been in place on the movement of risk goods from the property and it will be treated with fungicide. Surrounding areas are being searched for the disease.
This new find, along with a further three properties in Taranaki, brings the total number of confirmed infected properties to 16.
The majority of properties are in Taranaki with just two confirmed in Northland and the one new Waikato find, says MPI response director Geoff Gwynne.
The disease-causing fungus has been found at a mix of properties including nurseries, plant retailers and distributors, an orchard and private gardens.
The fungal plant disease was first found at a Kerikeri nursery in early May and then in Taranaki, before the King Country discovery.
Around 420 reports of rust have been made to officials and they are able to distinguish the highest risk reports from photographs.
Myrtle rust attacks native trees, such as pohutukawa and rata, and could cause serious damage to manuka trees, used in honey production.
There is no known method for controlling it in the wild, other than applying fungicide in very small areas.
MPI says it expects to continue to find new locations of infection as it was likely the fungal spores entered New Zealand from Australia during a major wind event.