Myrtle rust ravaging East Cape, with ramarama dying and pōhutukawa infected for the first time

Pōhutukawa, pictured here at Langs Beach in Northland, are susceptible to myrtle rust. Photo / File

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, pōhutukawa, 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.

East Coast 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, the infection started preventing mature trees from producing flowers and seeds.

By 2019, Atkins noticed young trees were dying, and just 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 Aktins, of Ngāti 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 of ramarama in seedling carpets."

Myrtle rust infection seen on a pōhutukawa near Lottin Point, East Cape, this week for the first time. Photo / Graeme Atkins

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 pōhutukawa, 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, which is a crucial food source for our tūī, bellbird, kākā, 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, and to lose this species would leave a massive food gap."

Over the past few years it appeared pōhutukawa might be showing some sort of resistance.

"We thought maybe pōhutukawa had a thicker shield on its leaves, or maybe because they grew close to the sea the salty breezes might protect them," said Atkins.

A dying ramarama tree on the East Cape. Photo / Roanne Sutherland

Then on Tuesday at Lottin Point, just west of Wharekāhika/Hicks Bay, he came across two mature pōhutukawa, about 20 metres tall, with some of their inner leaves laden with the distinctive rust-coloured fungal spores.

"It is devastating. All trees are special, but everyone has their favourite pōhutukawa.

"We've got a bach down near the local beach, perched under one. Here it signals fat fish, fat kina, it signals summer. I can't help but feel it could go the way of ramarama eventually - it is incredibly sad to find."

Myrtle rust, a disease affecting plants in the myrtle family, is caused by the pathogenic fungus Austropuccinia psidii.

Myrtle rust infects new plant tissue most easily, including leaves and new seedlings. Photo / Graeme Atkins

The windborne fungal disease has been spreading around the world with heavy infections leading to localised extinctions in places.

After arriving in Australia in 2010 westerly winds brought it across the Tasman Sea to Raoul Island in the Kermadecs in March 2017, where it was found in pōhutukawa trees.

In May 2017, it turned up for the first time on the New Zealand mainland, in Northland, in a Kerikeri nursery.

The disease has spread rapidly to Auckland, Te Puke, Waikato, Taranaki, Wellington, Tasman and even the South Island's West Coast.

However, it appears to have affected the East Cape most intensely, likely due to its abundance of native myrtle species and warm temperatures.

It has been found to affect ramarama most intensely, but it has also been found on the leaves of pōhutukawa and northern and southern rātā. So far it hasn't been found to infect wild mānuka.

Scion field technician Roanne Sutherland visited the East Cape last week with Atkins to see first hand the devastation.

"I've been monitoring myrtle rust in native forests for the last three years. We've had seedling death occur, but this is the first time the deaths of large, mature trees [in ramarama] have been reported."

Myrtle rust on the leaves of a ramarama tree. Photo / Roanne Sutherland

The wider ecological effects of losing a local species were unknown, Sutherland said.

"What birds and insects are going to be impacted by the loss of this species? What plants will take their place?"

Sutherland said it appeared parts of the East Cape had the "perfect" climate conditions for the fungal spores.

She also feared this summer, predicted to be extra hot and humid thanks to a La Nina system, could make things even worse.

The extent of myrtle rust across New Zealand was not well understood, nor was what could be done to stop the spread and how bad it could get, Sutherland said.

"It arrived in Australia in 2010, and they saw some localised extinctions after about four years. But we don't yet know what might happen here."

"Everybody has their favourite pōhutukawa," says DoC ranger Graeme Atkins. Photo / File

Researchers were working hard to understand the disease and develop management tools within the Beyond Myrtle Rust and Ngā Rākau Taketake research programmes.

However, long-term monitoring of native forests on a much greater scale than was currently taking place, was essential to measuring the impact of myrtle rust and to find natural resistance, Sutherland said.

The key was to closely monitor the spread of the disease, and to try and identify populations that appeared to show a form of resistance, Sutherland said.

The public could also play their role. If they came across myrtle rust, they should not touch the plant, but take a photo and upload the image to the iNaturalist app.

Atkins was hoping to get a local monitoring programme up and running with local hapū, to track the spread and find health populations of their taonga species.

"Who knows we might find a gully full of healthy ramarama that holds the key to resistance. All I can do is hope that is the case."