A disease threatening native trees and fruit crops in Northland has spread to a second site, the Ministry for Primary Industries (MPI) says.

Photo: Supplied

A biosecurity response team from the ministry has been in the region since the yellow fungus was found in Kerikeri last week.

Test results have confirmed the fungal plant infection is present at a second site in the town.

The ministry received the results this afternoon, confirming the infection at a private residential site on the same street as the originally-infected nursery.

A second nursery in the town had been under suspicion of having myrtle rust, but lab tests on samples proved negative.

The ministry was arranging re-testing of further samples to rule out a false negative result.

Its director of intelligence, planning and co-ordination, Geoff Gwyn, said today's find in a nearby garden was not unexpected, given the ability for myrtle rust to spread as invisible spores on the wind.

There would be conditions placed on the property to prevent the spread of the disease from the new site and affected plants would be treated, he said.

Further testing was being done.

Officials have been carrying out a high-priority search since the discovery of the first mainland case of the disease last Tuesday.

The ministry was doing everything it could to contain its spread, Mr Gwyn said earlier today.

Restricted notices were in place as a precaution until the result of the samples were confirmed.

Action to prepare for myrtle rust arriving in New Zealand had been ongoing since 2010, Mr Gwyn said.

Nursery that discovered disease hoping to be allowed back

Tom Lindesay, an owner of the nursery that detected myrtle rust last week, said he was hoping MPI would lift the quarantine on the nursery today.

Kerikeri Plant Production has been in lockdown since the fungus was found under the leaves of five pōhutukawa seedlings.

Mr Lindesay said the family business was impressed with the MPI staff who had been on site for days.

"They finished yesterday afternoon and it's just closed up at the moment and we're just waiting to find out whether we are allowed back to work there. They are going to let us know today sometime."

Mr Lindesay said, if the quarantine was lifted, he thought they would probably still face two or three weeks where they would not be able to trade.

The fungus originally from South America has been killing large numbers of native trees in Australia since 2010.

It spreads by air and is thought to be a threat to natives including pōhutukawa, rātā, mānuka and kānuka, as well as introduced species such as feijoas, guavas, gums, bottlebrush and other members of the myrtaceae family.

At this stage MPI was assuming that the outbreak came from the Eastern Coast of Australia, Mr Gwyn said.

NIWA would study wind plumes to help identify its point of origin and more research was being done to identify the particular strain of myrtle rust found in Kerikeri.