MAF Biosecurity New Zealand believes it has eradicated a potentially dangerous Australian insect, the southern saltmarsh mosquito.
Spraying to kill off the mosquito - a carrier in Australia of the debilitating Ross River virus - began over a decade ago when it was discovered in Napier.
Aerial spraying in the last site of infestation, in Marlborough, ended this week.
MAF Biosecurity says there have been no signs of the mosquito for a year, but it will be another 12 months before its eradication is certain.
Spokesperson David Yard says the $75 million cost of eradication has been worth it, as the health service would have incurred greater costs if the Ross River virus had become established in New Zealand