The Ministry for Primary Industries is "throwing the kitchen sink" at a plant disease found in Kerikeri.
Myrtle rust threatens native species such as the pohutukawa and manuka which would hurt the lucrative manuka honey industry.
About 50 MPI staff and contractors are in the Bay of Islands town in a bid to stop the spread of the fungus which has devastated some Australian plants since it was discovered there in 2010.
That number will be ramped up to 100 within days according to Primary Industries Minister Nathan Guy, who made a flying visit to Kerikeri yesterdayalong with Conservation Minister Maggie Barry, a sign of the seriousness of the incursion.
Ms Barry said Bay of Islands DoC staff had been taken off all but the most urgent duties and were checking conservation areas for any sign of the disease.
The fungus was found by the owners of Kerikeri Plant Production on Riddell Rd on Tuesday evening, who immediately notified MPI. Lab testing confirmed it was myrtle rust late on Wednesday.
Yesterdaythe nursery was in lockdown as contractors sprayed buildings with fungicide and MPI staff in white overalls inspected thousands of seedlings. A sign on the gate said the nursery was closed until further notice.
Geoff Gwyn, the head of MPI's response, said all plants in the nursery had been sprayed on Thursday and by the end of Friday all plant nurseries in the Kerikeri area would have been inspected.
Much effort was going into tracing all plant sales in the past three months. The nursery kept thorough records of its commercial sales but private sales were not recorded.
He urged anyone who had bought plants from any nurseries in the Kerikeri area recently to check their plants for signs of the disease. Infected plants had yellow pustules on the leaves, particularly on new growth, which then started to curl up and die.
Anyone who found signs of the fungus should take a photo and call MPI immediately. It should not be touched, he said. It could affect any of the 300 species of myrtle, including pohutukawa, rata, manuka, kanuka, feijoa, gum and bottle brush.
Restrictions had been placed on the nursery so nothing could be moved in or out, and MPI staff were checking all plants within 500m. Information leaflets were being printed and distributed, including at Kerikeri markets today and tomorrow.
Mr Gwyn said surveillance at 1400 "high risk" sites across New Zealand, including 800 in Northland, had been stepped up since the discovery of myrtle rust on Raoul Island, 1100km north of Cape Reinga, about two months ago.
He said MPI was "absolutely committed" to eradicating myrtle rust and was "throwing the kitchen sink at it".
However, it would be "naive and foolhardy" not to plan for long-term management of the disease. That included seed banking, resistance breeding and fungicide trials.
Lessons had been learned from Australia where authorities had waited six months before trying to eradicate the fungus, by which time it had become established in the wild.
Mr Gwyn said the nursery owners were not at fault and should be thanked for their diligence and prompt action.
The news has alarmed manuka honey producers who are already facing their worst season in many years.
Long-time beekeeper Graham Wilson, of Kerikeri, said the disease could be a huge blow to an increasingly important industry in Northland.
"But you have to suck it in and get on with it. Kiwifruit growers had PSA, everyone has their turn."
■ If you think any of your plants have signs of myrtle rust take a photo and call MPI immediately on 0800 80 90 66. Go to www.mpi.govt.nz for more information and photos of the fungus.
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