The Minister for Biosecurity says the fruit and vege lockdown in Devonport, Auckland will be in place for weeks.
A Queensland fruit fly was discovered in the North Shore suburb on Tuesday.
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The fruit fly is a serious threat to our horticulture industry and Minister for Biosecurity, Damien O'Connor, said protecting against an incursion is a costly business.
"A guestimate would be about $1 million per fruitfly," he said.
We hope it's just the one fruit fly, but we don't concerntrate on cost - we're just carrying out our plan," said Mr O'Connor.
The minister joined the field operation in Devonport, where a team of more than 60 people are working on the response. Another 20 are in Wellington.
Signs on Sunday went up on Devonport ferry terminal and arterial routes to inform locals about the Controlled Zone.
Biosecurity NZ's Catherine Duthie said so far, no further signs of fruit flies have been found.
"We are looking at likely pathways to entry it likely came in as - possibly as egg or larvae inside a fruit or vegetable - but like most incursions, we are very unlikely to know how it came in," she said.
Bins are now going into the Controlled Area for safe waste disposal, as a fruit and vegetable lockdown remains in place in Devonport.
No fresh fruit or vegetables can be taken outside a 200-metre radius of where the fruit fly was found, while no homegrown fruit or vegetables can be moved beyond the wider zone B.
Leafy and root vegetables are exempt.
"We have a lot of people on the ground, but we are relying on people to support the programme to check fruit and veges and help in any way," said Mr O'Connor.
This is the fifth time a Queensland fruit fly has been discovered in the upper North Island in the past 10 years.
Only once has a population been found. That was four years ago, and it took $16 million and 10 months to eradicate.