Jamie Morton is the NZ Herald's science reporter.

Myrtle rust implications for NZ still unclear

A worker sprays a building at Kerikeri Plant Production where the fungal disease was first discovered. Photo / File
A worker sprays a building at Kerikeri Plant Production where the fungal disease was first discovered. Photo / File

What myrtle rust could mean for New Zealand remains unclear, say biosecurity officials battling to contain the major fungal disease's incursion in Northland.

The discovery of myrtle rust at a Kerikeri plant nursery last week holds potentially devastating implications for myrtle trees such as pohutukawa, manuka, bottlebrush and feijoa, and has sparked a major biosecurity operation by the Ministry for Primary Industries (MPI), the Department of Conservation (DoC) and other agencies.

Kerikeri Plant Production, where the fungus was first found, remains under lockdown, while a 100-strong team of officials has completed checking all properties within the incursion's 500m-radius ground zero.

There were now two confirmed properties where myrtle rust has been found: Kerikeri Plant Production and a neighbouring residential property where the disease had been isolated on one tree.

Geoff Gwyn, the MPI director heading the response, said there were also two other locations where there had been a "suspected" find.

One was another Kerikeri plant nursery, which lab tests had since cleared, and a further neighbouring property to Kerikeri Plant Production, where sampling and testing was underway.

Checks were today being made on a slightly wider area, taking in the new confirmed find in the same road, with all suspect and confirmed infected properties under a restricted place notice, Gwyn said.

"This means there are controls on the movement of materials from the sites and people need to take precautions to ensure their clothing and footwear is clean prior to leaving the properties."

Gwyn said while MPI was trying to do the best job possible to prevent the spread.

"We have to be realistic, though, that this is a disease that spreads by microscopic spores that can be carried by the wind and on people, vehicles and equipment," he said.

Containing it may not be possible, he said, and there had never been a successful eradication of myrtle rust anywhere in the world.

Biosecurity officials battling to contain a major fungal disease in Northland still can't say what the incursion could mean for New Zealand. Photo / File
Biosecurity officials battling to contain a major fungal disease in Northland still can't say what the incursion could mean for New Zealand. Photo / File

"We do not know yet what the impacts of this might be on myrtle species in New Zealand.

"We know that internationally its effects have varied from country to country and plant to plant."

Scientists Dr Andrea Byrom and Dr Amanda Black earlier told the Herald the threat to New Zealand species was "real" and sectors - particularly the $300 million manuka honey industry - would be scrambling to react as soon as there was more information.

The extent of the effects for each species like New Zealand manuka were yet to be quantified, mainly because scientists had previously been unable to carry out extensive research on our plants because the disease was still undetected here.

But any loss in plant function would mean that the manuka honey industry would be affected, because the window for honey production was short and manuka was not generally the preferred food for bees if they had other options available, like fields of clover.

They characterised myrtle rust as far more widespread and mobile than biosecurity disasters kauri dieback disease and Psa-V, both of which were soil-borne pathogens.

Gwyn said his team had received a positive response from Northland residents providing useful information, including a number of potential finds which they're looking into.

• If you think you've seen signs of myrtle rust, don't touch it or the plant. Take a photo and call MPI on 0800 80 99 66.

- NZ Herald

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