Can we save iconic plants from myrtle rust?
The invasive fungal pathogen is decimating forests – but research and field trials offer hope.
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Myrtle rust on ramarama leaves. Image credit: Peter de Lange.
It’s been six years since myrtle rust was first detected in mainland New Zealand, after winds carried the invasive fungal pathogen across the Tasman Sea from Australia. Since then, the orange spores have infected trees across the North Island and into parts of the South Island. The fungus attacks soft new leaves, shoot-tips and stems, and can result in plant death. Iconic species such as pōhutukawa, ramarama, rōhutu and rātā – which are all part of the myrtle family – are susceptible.
Dr Stuart Fraser, a forest pathologist, says that Scion Research monitoring sites in the Bay of Plenty are being hammered by myrtle rust. “You see a pretty devastating impact on Lophomytrus species [e.g. ramarama]. You just see them in a terrible state.” Pōhutukawa also got hit pretty hard for the first time this summer, Fraser says, “I saw one tree and it was the worst I’ve ever seen.”
We will lose populations if we don’t do something, according to Stuart – but luckily, plenty of people are doing lots of brilliant research and field trials to stop the spread.
Field trials show promising results
The Āwhitu Peninsula is home to one of the last remaining stands of rōhutu in the Auckland region – a “nationally critical” species. Here, Dr Michael Bartlett from Scion has been monitoring rōhutu since 2019, watching as the plants steadily decline. But in 2022, funding from Auckland Council allowed Āwhitu Landcare to undertake a trial with 27 plants, applying a rotating regimen of fungicides over spring and summer. By December last year, when Fraser visited the site, the trees were “a lot happier and healthier,” he says. Specimens were in flower and fruit was beginning to set, with very little sign of myrtle rust. “If nothing had been done, they would’ve just died,” says Fraser. The trials are set to continue this year.
Remote sensing tech enhances detection
Myrtle rust infection can now be detected even before the bright orange rust appears, thanks to Scion researchers led by data scientist Elizaveta Graevskaya. Using a rose apple plant deliberately inoculated with the fungus, the Scion team deployed thermal imaging to detect a dip in leaf temperature up to one day before the infection showed its orange spots. A hyperspectral sensor, which detects changes in the colour of the leaf, could pick up infections even earlier: up to three days before visible symptoms. Early detection is comparable to Covid-19 testing: the sooner you pick up sick plants, the better your chances of stopping the spread. While the sensors aren’t ready for wider roll-out yet, the Scion team are excited about the possibilities of handheld myrtle rust detectors in nurseries, and even adapting the tech for use in the field.
There’s plenty more in the works, says Fraser, including research into myrtle rust’s genetics, life cycle and reproduction – and the little fly that appears to munch on myrtle rust too. While we’ll never be able to eradicate myrtle rust, all this activity gives Fraser hope that we can save species: “If we can mobilise people, if we can give people tools and resources and funding, then I definitely have hope.”
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Post-Paora palaver, more kiwi news
The controversy ignited last week, when videos of a captive kiwi named Paora in Miami went viral, has raised questions about why kiwi are overseas in the first place. The NZ Herald’s Jamie Morton outlines where (and why) around 60 kiwi are overseas. It’s also sparked reflection on how we treat kiwi here at home: Kate Green from RNZ reports that Cape Sanctuary in Hawke’s Bay is under investigation for its treatment of resident kiwi, including offering kiwi encounters with a licence. For some more positive news about our national bird, the latest Side Eye comic from Toby Morris tells the story of the Capital Kiwi Project, returning North Island brown kiwi to the wild corners of Wellington.
The carbon offsets controversies continue
A New Zealand carbon offset company is claiming it meets standards set by a new watchdog – except the watchdog hasn’t even started evaluations yet, Olivia Wannan reports for Stuff. Overseas, fallout from The Guardian’s big investigation into “worthless” rainforest credits proffered by Verra continues, with the company’s CEO stepping down. The Guardian has continued exposing “junk” offsets, with new analysis revealing that fossil fuel giant Chevron’s climate pledge relies on “environmentally problematic” offsets and “unviable” technology.
Keep your eyes peeled for this invasive clam
The highly invasive gold clam has been found growing in the Waikato River, the first time this species has been detected in New Zealand. The gold clam is a prolific breeder, reaching densities that can clog infrastructure and potentially out-compete our native freshwater mussels. MPI is deploying environmental DNA (eDNA) technology to try to figure out how far the clam has spread, but you can help too, by learning what the gold clam looks like and reporting sightings. In other invasive species news, the superspreader seaweed Caulerpa has been discovered in more than a dozen Bay of Islands locations, after spreading to the mainland from Aotea Great Barrier Island.
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Kiwi scientists are working on a livestock vaccine to reduce their methane-producing prowess, but it’s still a decade away
France has ostensibly banned short-haul flights (<2.5 hours) this week, but this New York Times article explains that there are so many exceptions that the ban is practically toothless
In the wake of last Friday’s Global Climate Strike, Newsroom’s Marc Daalder comments that young people have a right to be angry. (More on young people and climate in this past issue of Future Proof)
Also on Newsroom, Nikki Mandow takes a look at polarising carbon capture tech in a New Zealand context
Scientists are worried about flaws in a database meant to capture deep-sea biodiversity, as the International Seabed Authority faces its first request for mining authorisation coming up in July
To finish this issue, a pod of killer whales off the Iberian Peninsula have taken to ramming into boats, chewing on rudders and in some cases even sinking vessels. These intelligent animals have a fearsome reputation, but this type of behaviour is considered unusual. National Geographic reports that the pod is led by a matriarch called White Gladis. A new research paper speculates that Gladis may have it in for boats after being involved in an accident with one – but not everyone is convinced by that explanation. Maybe they’re just doing it for fun. For more interesting orca behaviour, earlier this year I covered some recent New Zealand research on orca-sunfish interactions, featuring sunfish frisbees and a move called the “mola moustache”.
Have a killer week,
Ellen
Got some feedback about Future Proof or topics you’d like covered? Get in touch with me at futureproof@thespinoff.co.nz
