Extinction for some native plants could become a reality following the first known mature tree death in the East Cape due to myrtle rust infection, Manaaki Whenua – Landcare Research has announced.
The research institute has partnered with Biosecurity New Zealand to develop the NZ Myrtaceae Key – an easy-to-use free app for citizen biosecurity volunteers.
SCION myrtle rust researcher Roanne Sutherland had been monitoring the fungus for the last three years and had seen seedling death.
"This is the first time the deaths of large, mature trees have been reported."
The fungus is windborne and arrived on westerly winds from Australia in 2017.
Myrtle rust has now spread across the North Island and parts of the South Island, threatening New Zealand's native myrtles, including pōhutukawa and mānuka.
"The wider ecological effects of this are unknown," Sutherland said.
"What birds and insects are going to be impacted by the loss of this species? What plants will take their place?"
Dead trees were first observed this spring by Graeme Atkins, a local ranger who has worked for the Department of Conservation for 26 years.
Atkins found infected plants in the East Cape in 2018. However, by then it had been acknowledged that myrtle rust could not be permanently eradicated, and efforts had moved on to management and research.
Atkins has detected infection on several species, although ramarama and rohutu have been hardest hit in the East Cape.
People keen to support the fight against myrtle rust, which threatens many native trees, shrubs, and climbers, now have a new tool to help identify vulnerable plants in the myrtle family.
Manaaki Whenua – Landcare Research and Biosecurity New Zealand have partnered in the development of the NZ Myrtaceae Key – an easy-to-use free app for citizen biosecurity volunteers.
The app will help to identify susceptible plants and keep an eye out for the fungal disease myrtle rust.
Myrtle rust has already spread across the top half of the North Island and cases have been recorded as far south as Greymouth.
Ministry for Primary Industries diagnostics and surveillance services director Veronica Herrera said science partnerships like this would help the country stay on top of plant pests and diseases.
The NZ Myrtaceae Key is a Lucid identification tool envisaged and funded by Biosecurity New Zealand and developed by botanists from Manaaki Whenua, the National Forestry Herbarium, Unitec, and other experts.
The app is interactive and comprehensively illustrated with more than 1,600 fully captioned images built in, and is available for both iPhone and Android smartphones.
Herrera said the key included more than 100 of the most commonly found Myrtaceae species, subspecies, hybrids, and cultivars in New Zealand.
"Of these, 27 species, such as the iconic pōhutukawa, mānuka, and kānuka, are indigenous to New Zealand: others, such as feijoa and eucalyptus, are exotics of economic importance."
Manaaki Whenua – Landcare Research researcher Murray Dawson said the arrival of the windborne myrtle rust in 2017 gave a new importance to being able to identify Myrtaceae as heavily infected plants inevitably die.
"The disease is a threat to the important and substantial mānuka and kānuka honey industry. Using the new app to accurately identify species of Myrtaceae in New Zealand will make it easier to monitor and report cases of myrtle rust.
"By using the key, anyone, from farmers and trampers to gardeners and park users, will be able to identify plants to check for and report the tell-tale yellow spores, and diseased leaves," says Mr Dawson.
How to use the app
Enter in the characteristics of the plant and the app sorts plants with these features, progressively choosing different features, eventually narrowing the results to just one or a few matches.
Once the plant in the myrtle family has been idenified, and the app-user thinks they see signs of the disease on it, don't touch it.
Take a photo and submit it to the iNaturalist website. Experts can check to confirm whether it is myrtle rust.
This information makes it available to agencies and scientists to analyse the rate of spread and observed impacts.