‘Devastating’ tree deaths
Myrtle rust killing mature natives on East Cape: Scientists
The first cases of mature native trees dying from myrtle rust have been recorded, with scientists warning localised extinctions could soon be a reality.
The “devastating” discovery, in a valley of ramarama on the North Island’s East Cape, comes as the windborne fungal disease has also been found to have infected our native Christmas tree, po¯hutukawa, there for the first time.
Myrtle rust was first discovered in New Zealand in 2017, having blown over from Australia’s east coast, where it has led to localised extinctions in myrtle species.
Department of Conservation ranger Graeme Atkins first spotted the fungal disease in ramarama, a shrub that grows 8 to 10 metres high, in the East Cape in April 2018.
By that stage it was accepted the national war against myrtle rust was lost, and efforts had moved on to management and research, including seed banking and seeking out resistant populations.
At first myrtle rust seemed to proliferate in summer, also among rohutu, and die down during the cooler months. But now it was there year around, thriving.
Since myrtle rust infects new plant tissue most easily, seedling carpets were the first to die off. Then it started preventing mature trees from producing flowers and seeds.
By 2019, Atkins noticed young trees were dying, and this year he found fully mature trees dying — the first known cases in the country.
“I think in two years ramarama could be all gone,” said Ruatoria-based Atkins, of Nga¯ti Porou and a ranger of 26 years.
“If someone told me four years ago ramarama was going to be on the threatened plants list, I would have laughed. Where I live there are tens of thousands if not hundreds of thousands . . . in seedling carpets.”
Without adult trees, there will be no seeds, no more seedling carpets and no possibility of recruitment.
Ultimately, ramarama could disappear from the local environment.
While it is not a “celebrity tree” like po¯hutukawa, Atkins said it had huge cultural and ecological values.
“It is a beautiful shrub that has beautiful flowering, and is found in many home gardens. It has heaps of nectar, a crucial food source for our tu¯¯ı, bellbird, ka¯ka¯, and bats in the past.
“But most crucially, it has loads of fruit on it through the winter, which is critical for the survival of our birds, lizards and bat. To lose this species would leave a massive food gap.”
On Tuesday at Lottin Point, west of Whareka¯hika/Hicks Bay, Atkins found two mature po¯hutukawa, about 20m tall, with some of their inner leaves laden with the distinctive rust-coloured fungal spores.
“It is devastating . . . I can’t help but feel it could go the way of ramarama eventually.”
Myrtle rust, affecting plants in the myrtle family, is caused by the pathogenic fungus Austropuccinia psidii.
The windborne fungal disease has been spreading around the world with heavy infections leading to localised extinctions in places.
Since May 2017 it has spread to Auckland, Te Puke, Waikato, Taranaki, Wellington and further south.