New Zealand's Ministry for Primary Industries says it believes the insect to be part of the same localised population as previous detections in the Grey Lynn area of Auckland.

The news comes as Auckland is yet to decide on what to do with next month's annual celebration of Polynesian culture at Western Springs, well inside the fruit fly control area.

The Queensland fruit fly, if it became established here, would represent a major threat to New Zealand's $2.6 billion horticultural export trade.

Following the discovery of a fifth fly, MPI's chief operations officer said there would be no changes to the control area.

"We have been expecting to find more flies so the latest detection is no surprise and confirms that the trapping systems continue to be successful," Andrew Coleman said.

"The find was close to the original detections so we believe the fly is likely to be part of the same population."

MPI has more than 180 staff working in the field on the response.

The response involves the use of movement controls, traps, public awareness and treatment. Stricter controls continue to be applied at New Zealand's borders.

Ground-based spraying has also been completed under the fruiting trees where positive finds have been made.

"We continue to appreciate the outstanding public support we have received for our movement controls," Coleman said.

"We have every confidence that our measures will effectively eradicate this population."

Auckland's Pacifika Festival, the biggest celebration of Pacific Island culture in the world, is due to be held on March 14 and 15.

Auckland's events agency ATEED and the Ministry of Primary Industries (MPI) are in discussions about whether the event may have to be moved to another location while the effort to eradicate the pest continues.

"Discussions are ongoing, with no final decision being reached today," an MPI spokesman said.

ATEED said there were a wide range of possible alternative sites, from Ellerslie Racecourse to one of the regional parks.

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No whole fresh fruit or vegetables, except for leafy and root vegetables, can be taken outside a controlled zone.

Over 80,000 people are expected to attend Pasifika, where villages representing the various Pacific Island cultures put on performances and sell food and hand made crafts.

MPI has not extended the controlled area since the fourth fruit fly was found on the weekend.

Residents within the smaller central "zone A" are being asked to dispose of all store-bought fruit and vegetable waste in special disposal bins that have been provided by MPI.

Zone A residents are being asked to leave any home-grown fallen fruit on the ground in their garden for inspection by MPI.