Biosecurity officials hope to declare Auckland's Grey Lynn free of Queensland fruit fly by Christmas.
The warmer spring months will see any flies that survived winter take to the air, and hopefully to their doom, the Ministry for Primary Industries says.
"Now that the weather's warming up, if any flies did manage to survive the earlier treatment blitz, they'd be on the wing and we'd trap them in our extensive network of lure traps," said planning manager Edwin Ainley.
MPI had increased its checking of the surveillance traps and was confident the fly had been eradicated.
But Mr Ainley said it needed these next couple of months of trapping to verify this.
"We can't assure our trading partners that the population is gone until the empty traps confirm our success. At this stage, we hope to declare eradication and end the movement controls on fruit and veges before Christmas."
Fourteen fruit flies were found in traps in February and March, but none since, prompting restrictions on the movement of fruit in the area.
New Zealand exports about $2.5 billion worth of fruit and vegetables each year and the domestic market is estimated to be worth $4b. A fruit fly invasion could render the fruit unsalable.