An invasive weed that can reduce water quality and block irrigation systems has been discovered in the Waikato River.
"New Zealand cannot afford to let its guard down despite no further fruit flies being found in Whangarei," O'Connor says.
"An infestation of Queensland fruit flies would have a devastating effect on our horticulture industry. They are the horticulture equivalent of foot and mouth disease.
"The Whangarei ports said it didn't arrive via its facilities because no produce is imported on its docks.
"We still don't know how the fly got here. It is important we know so we can protect our valuable industries from the decimation these flies have caused on Australian crops.
"Other routes into the country such as recreational yachts must be considered.
"New Zealand has been let off with a warning. Next time we won't be so lucky.
"This Government has run our biosecurity services into the ground. Our biosecurity resources are spread so thin, officers would be seriously stretched by a large-scale infestation."