International yachts arriving in Northland this summer will be scrutinised by officials carrying out extra biosecurity checks to prevent fruit fly entering the country.

The Ministry of Primary Industries has teamed up with customs and the New Zealand Defence Force (NZDF) and focusing on Northland ports where most international vessels arrive in the country.

MPI quarantine officers will also work with the Royal New Zealand Air Force P-3K2 Orion aircraft and the Royal New Zealand Navy's Seasprite helicopters and carry out surveillance of the Northland coastline.

The Orion aircraft will provide early warning of yacht arrivals, while the Seasprite conduct surveillance of the Northland coastline and ensure all vessels are checked.

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The NZDF's surveillance missions will help identify incoming yachts and look for any boats that try to seek shelter in local coastal bays prior to arriving at their designated port of arrival - an offence under the Biosecurity Act.

Two extra MPI staff will be based at Opua for the season, and other biosecurity staff would be available to help out during busy periods.

"The primary driver for this operation is to mitigate the biosecurity risk posed by fruit fly," MPI spokesman James Reed said.

"An outbreak of fruit fly would have a significant and detrimental effect on New Zealand's horticulture industry and on New Zealand's international trade."

Single Queensland fruit flies were detected on two separate occasions in Whangarei in 2014.

One male Queensland fruit fly was found in a garden in the Riverside/Parihaka area, on January 21.

The scare cost taxpayers almost $1.6 million, but it was money well spent to protect the important sector, the man in charge of the biosecurity operation said.

The second scare occurred in April, when a single fly was discovered 400m from where the January fruit fly was detected.

MPI said in both instances it was unclear how the fly arrived in New Zealand.

Around 500 international boats were predicted to arrive in Northland over the next few months.

There were two authorised ports of first entry for visiting boats in Northland - Marsden Cove and Opua.

It was expected 85 per cent of all boats arriving in the country would arrive in Opua and 10 per cent would arrive in Marsden Cove. The remaining 5 per cent are spread around other ports in New Zealand.

MPI were planning to send biosecurity detector dogs to Northland to help with yacht inspections.