Mount Roskill residents will have to stick to exclusion zones for fruit and vegetables for at least another week and a half.
That's while officials make sure the Queensland fruit fly that's been discovered there is on its own.
Ministry for Primary Industries spokesman Andrew Coleman says they're following international recommendations.
"And unfortunately it is a two week period, which might seem a long time, but after that you're reasonably sure that that was the only fruit fly that was that there."
Mr Coleman says residents need to realise how serious the situation is, and not take fruit or vegetables outside the zones.
Who would have guessed a fruit fly could be so expensive? The operation could cost millions.
Mr Carter says as the exercise heads into its fourth day, he expects it to go on for another couple of weeks.
"The exercise could cost in the realm of three of four million dollars but it does depend on how long the exercise goes on for which of course does depend on whether we find any more fruit flies."
Mr Carter says the threat to the industry is huge and the exercise is well worth the money.