There's concern not enough is being done to monitor the spread of myrtle rust throughout New Zealand.
It comes after the wind-borne fungal disease, which can infect natives like Pohutukawa and Rātā, has been identified in Auckland's Waitākere Ranges for the first time.
The disease was spotted on a branch of Ramarama by two friends hiking through the Regional Park, who are self proclaimed "plant nerds".
"We're always checking out all the different plants around us trying to identify them", said Harrison Sollis.
"We noticed Ramarama which we know is quite a severely affected plant by myrtle rust... after looking at some of the new growth, Eliah discovered some of the myrtle rust pustules on the leaf," he said.
Eliah Murdoch-Pike added: "At first I was surprised and then I was pretty disappointed to have found it... although we don't want it to be here we do need to find it wherever it is."
The pair who discovered more infected leaves today with 1 NEWS, logged their finding on the platform iNaturalist and realised it was a first.
"When we recorded it we were able to see all the other recordings... but in the Waitaks, there was none... that's when it hit home, this was pretty bad," said Murdoch-Pike.
Murray Fea, Auckland Council senior plant pathogens advisor, said people should look out for "yellow dust".
"It's unfortunate myrtle rust has been found in the park boundary...although it's not surprising this has happened 'cause Myrtle Rust has been in the area of West Auckland for a long time."
In a statement, Landcare Research says people in New Zealand should be concerned, "given myrtle species (targeted by the disease) are throughout the ranges."
It says the disease has likely been in the park for many months.
"It can be difficult to see and there is currently a lack of systematic, nationwide monitoring/surveillance for this disease," the organisation said.
The disease was first found in New Zealand in 2017.
In a statement, the Ministry for Primary Industries said: "MPI funded research was completed mid-2019 ($3.7m over two years). We no longer fund science or undertake surveillance for myrtle rust or activities to manage it."
Joris De Bres, an environmental campaigner from Project Crimson, said because of that "we have no idea just how far myrtle rust has spread and to what extent it has spread within the regions that it's spread too."
"We want to know and we want other people to know just how bad this is. The last time that there was national monitoring, co-ordinated monitoring, was a year and a half ago", he said.
"Pohutukawa and Rātā, these are iconic New Zealand native trees and any extensive damage to those is really a fundamental change to our landscape."
Fea told 1 NEWS myrtle rust wouldn't knock a plant out suddenly, but does infect the new growth of plants.
"If it keeps destroying those over repeated seasons, the plant may run out of energy and succumb to the infection," he said.
“There's concerns about the longevity of the Ramarama plants in this population, luckily it seems this particular stand has been able to put on new growth despite the myrtle rust and there's also new seedlings that aren't infected."
Landcare Research recommends avoiding planting non-native myrtles, like the popular garden plant, Lilly Pilly. It also recommends removing such non-native myrtles.
“These are susceptible to myrtle rust and they can form a reservoir population for the disease," said Fea.
He advises dealing with the plants in cold and drier months, as that’s when myrtle rust is less of a risk.
“It is a tropical disease and prefers warm temperatures," he said.