Pohutukawa flowers on Mauao, looking down Mount Main Beach. Photo / Alan Gibson
Pohutukawa flowers on Mauao, looking down Mount Main Beach. Photo / Alan Gibson
Teams working to prevent the spread of myrtle rust detected on Mauao in Mount Maunganui are warning people to stay away from pōhutukawa trees on the mountain.
This is to prevent people from spreading myrtle rust from tree to tree, Mauao Trust kaitiaki group facilitator KawanaWarahi said.
Myrtle rust first appeared in New Zealand in 2017, raising concerns it could threaten myrtle-family species such as mānuka, feijoa, and kānuka.
These species, which Warahi described as “money trees”, have so far escaped damage from myrtle rust. But other trees, like the pōhutukawa on Mauao, and ramarama in Rotorua, have been hit hard.
“Rotorua has already lost the ramarama,” Warahi said.
“It then sticks around for a few months and dwindles off as it gets cooler.”
There are currently no conclusive methods to eliminate the disease.
While herbicides may suppress it temporarily, McLeod said it remained unclear whether they actually eradicated the pathogen.
“There is still research to be done on our part around that.”
One proposed mitigation measure is a seed bank, where pōhutukawa trees would be cloned from cuttings, rather than growing from seed, which takes decades, said McLeod.
Mauao is jointly administered by the Mauao Trust and Tauranga City Council, and the project is funded by Genomics Aotearoa — a national research initiative supporting the use of advanced genomics and bioinformatics in health, the environment, and primary industries.
Pohutukawa flowers on Mauao, looking down Mount Main Beach. Photo / Alan Gibson
Three varieties of pōhutukawa grow on Mauao: Pītau pōhutukawa, Kermadec pōhutukawa, and a hybrid formed from the merging of native and introduced types.
The Kermadec variety originates from the Kermadec Islands, more than 1000km northeast of Aotearoa.
Now the northeast side of Mauao has been affected by myrtle rust, with the pathogen blowing across from Australia, McLeod said.
“A whole lot of planting was done, and nobody knew that there were different types.” Taranaki iwi consider the Kermadec variety a taonga species, brought over by their ancestors on waka centuries ago, she said.
Hybridisation — the mixing of two different species to produce a new form with combined traits — contributed to the decline of native eucalyptus in Australia, Warahi said.
To identify the pōhutukawa on Mauao, Warahi analysed 4000 leaves from 200 trees to determine key traits.
The team of kaitiaki, all with ancestral ties to Mauao. Photo/ Brydie Thompson.
This enabled the kaitiaki to begin identifying individual trees across the maunga.
His team then employed artificial intelligence, using satellite imagery and deep learning to map the canopy.
“We managed to get to around 580 pōhutukawa trees,” he said.
Hybrids pose a threat to native species and could eventually replace them, Warahi warned.