Biosecurity staff fear the deadly myrtle rust plant disease could spread across Auckland as they scour an infected farm in the region.
The Ministry for Primary Industries says the city's warm, humid weather provides the perfect conditions for the wind-borne disease to spread.
Biosecurity on a military scale, serious precautions are being taken to contain the disease.
Will Frances's family planted ramarama trees four decades ago. They sell the foliage to florists.
Now infected with the deadly myrtle rust fungus, hundreds of trees have to be ripped out.
"We've made a living off them for 40 years," he said. "We have other crops, but a good portion of our income will probably no longer be there."
Myrtle rust spores are microscopic and spread across large distances on the wind.
"I think, under the right conditions, which is humidity and warmth, it will spread quite rapidly," said myrtle rust response controller Dr Catherine Duthie.
"This is a wind-borne disease. We think that it originally came over from Australia on the wind, so if it's capable of spreading from Australia to NZ, then it's capable of spreading a lot further."
The Waimauku outbreak is the largest on an individual property, and is surrounded by farmland and large stretches of native bush.
Neighbours, including a large nursery, told Newshub that they're very concerned.
They've been checking plants, but so far, there have been no other reports of myrtle rust in the area.
Native trees at risk include pohutukawa, manuka, kanuka and rata.
MPI wants anyone who spots myrtle rust to alert them.