The failure to find any more Tau flies in south Auckland is proof the country's pest prevention measures are working well, says the Ministry for Primary Industries (MPI).
The agency has now confirmed the male fly found in a south Auckland trap a fortnight ago was a lone invader and surveillance manager Brendan Gould suspects the tropical fly hitched a ride into New Zealand as a larva attached to a piece of fruit.
"It was a bit of an odd one. It's a tropical species so it could well be a one-off," says Mr Gould. "We've got great measures at the border and we have our surveillance in the post-border space so we're fairly confident if one does come we'll pick it up again."
He says the response by MPI was warranted.
"It's the same approach we use for any fruit fly, it's very robust, it's worked for us several times before, it's internationally recognised the approach we apply, so I don’t think it was over-the-top. And you just have to look at the size of the horticulture industry that would be impacted."
The Tau fly is a threat to a number of crops, including pumpkins, melons, cucumbers and passionfruit.
Mr Gould says it's "extremely unlikely" the Tau could have established itself here because of the country's climate.