Myrtle rust fears for native flora
Conservation Minister warns of possible ‘localised extinctions’
While some growers feel like they have dodged a myrtle rust bullet, others have concerns the plant disease will kill off native flora.
Myrtle rust was found for the first time in New Zealand five years ago, posing a threat to native species.
The Bay of Plenty was one of the first regions impacted, and it soon became obvious the disease could not be contained. It became widely dispersed throughout the North Island.
The disease has been reported throughout the region, including Tauranga and Rotorua, and threatens native myrtle species such as po¯hutukawa, ma¯nuka and ra¯ta¯.
Feijoa growers were also thought to be affected.
But NZ Feijoa Growers Association manager Ian Turk said the industry had since been struck off the list of those at risk.
“We’ve dodged a bullet there. We’re just keeping an eye on it.”
Comvita head of industry affairs Tony Wright said it monitored for the disease across the whole of its ma¯nuka operations and there had been no issues.
“It’s been a bit of a non-event, really.”
He said the company had done its research and had worked to understand the sensitivity of ma¯nuka to myrtle rust.
“It demonstrated ma¯nuka has a pretty high level of natural resistance.”
Other species were less resistant, however. While not native, the popular hedging plant “lilly pilly” appeared to be susceptible.
Te Puna-based Grower Direct nursery and landscapers owner Paul Nielsen said, in his experience, it “almost exclusively” affected that plant.
However, most of the time the client had no idea what it was that painted their plant with the yellow fuzz.
He recently ripped out a whole hedge with an owner’s approval, after he told her what it was.
The response had shifted from containment to research in 2018, and late last year the Government announced a Jobs for Nature-funded collaboration.
Conservation Minister Kiri Allan said the disease posed a threat to some of the most abundant native myrtle species, as well as a threat to the ma¯nuka and ka¯nuka honey industry.
There were two projects, including one in the Bay of Plenty, to focus on monitoring myrtle rust infestation, mapping its spread and ramping up the propagation of plants showing the most resistance to the disease.
She said the effects of the disease were becoming increasingly apparent.
“Overseas experience indicates localised extinctions are something we need to be prepared for.”
It led to a loss of biodiversity, which in turn impacted the wider ecosystem and cultural identity, she said.
The project, based in Rotorua, would identify where the most vulnerable myrtle species were in native forests in the Bay of Plenty region, determine the extent of each population and record the incidence and severity of myrtle rust within them.
Cuttings will be taken and seed collections started with the intention of establishing a resistance-breeding programme.
Scion was leading the recently launched project and Ka¯uru coleader Mariana Te Rangi said many of the things New Zealanders enjoy could disappear if the disease spread out of control.
Death of mature ramarama trees had been recently observed in the East Cape and the disease was escalating in the Bay of Plenty.
Scion scientist Heidi Dungey said while the work would not prevent infections, it would help with understanding when and where the most susceptible myrtle species were within the region and provide ways to support them.
Biosecurity New Zealand’s pest management group manager John Sanson said not all native myrtle species were equally susceptible to myrtle rust.
“While plants like ma¯ nuka, ka¯ nuka and rawiri ma¯nuka show some level of resistance, other native species like po¯hutukawa, ra¯ta¯ and swamp maire (waiwaka) are more susceptible to the disease.”
If people suspect they have found myrtle rust they should photograph it and send the photo to the inaturalist website, where experts can check and confirm whether the observations are correct, he said.
We’ve dodged a bullet there. We’re just keeping an eye on it. NZ Feijoa Growers Association manager Ian Turk