Days after an infestation was found on a ship in New Plymouth, hundreds of Australian plague soldier beetles have been gassed on another ship in Wellington.
The beetles are a prohibited pest in New Zealand because of fears they could carry diseases and devour native insects.
Primary Industries Ministry enforcement staff interviewed the captain of the AAL Brisbane in Wellington on Thursday and could charge him for failing to declare the beetles.
Another beetle-infested ship docked in New Plymouth earlier this month.
Geoff Gwyn, of the border clearance service, said the ministry was already on high alert when the AAL Brisbane arrived.
"The vessel underwent a full inspection. It was found to be literally crawling with hundreds of beetles," he said.
The ship was fumigated and the port checked for surviving beetles, none of which were found, he said.
It was unknown what impact the beetles would have on New Zealand, but overseas they were deliberately used to control other insects, such as aphids. "They could eat our indigenous insects," Mr Gwyn said.
Australian Museum entomologist Chris Reid said the beetles could have a huge impact on New Zealand.
'They are generalist and they appear in huge masses," he said. "Introduce something like this with no control mechanism, and who knows what would happen."
The plague soldier beetle is about 1.3cm long, with a green back and an orange collar. They are native to Australia, where they form large swarms and infest gardens from spring through till autumn.
The swarms can be so large that they weigh down plants, but usually the beetles are more intent on mating than eating.
One study found that, on a plant holding a swarm of beetles, 92 per cent were copulating.
It is the second time the AAL Brisbane has been detained in Wellington.
In August, the ship was stopped after it was nearly involved in a collision at Pencarrow Head.
The ship's listed New Zealand agent, Seaway Agencies, referred all questions to another agency, Concept Cargo, which acts for the ship's owner, Austral Asia Line, in New Zealand.
Cargo Concept's New Zealand managing director Elizabeth Bentley did not respond to repeated calls from Fairfax Media yesterday.
The ship is now in Tauranga but will not be detained. Fairfax NZ
- Taranaki Daily News
Should councils hold by-elections?
View marriage and birth notices from around the region
View obituaries from around the region