Biosecurity New Zealand is asking the public to report any sign of the wood-boring granulate ambrosia beetle.
The unwanted pest has been detected in 5 Auckland areas since 20 February.
This is the first time the beetle has been found in New Zealand. While it is unclear how the beetle arrived in New Zealand, the evidence to date suggests it may have been in the country for at least 2 years.
The beetle is regarded as a serious pest overseas. It is known to damage a wide range of broadleaf trees, including horticultural species such as avocado, and can spread fungal diseases.
Biosecurity New Zealand is currently assessing the potential risk from the beetle to New Zealand, says Brendan Gould, biosecurity surveillance and incursion manager.
"We need to know if New Zealand has a wider population, which is why we are asking the public to report any possible sightings."
The beetle resides under bark, making it difficult to detect.
Mr Gould says a tell-tale sign is distinctive protrusions of frass (compacted sawdust) from bark that look like toothpicks. They are caused by the beetles pushing frass out of tunnels bored into the trees. Other symptoms include sap oozing from the tunnel entrances and branch dieback.
He says officials are working with local authorities to identify the extent of the spread, including inspecting known host trees and placing lured traps around the detection sites.
Biosecurity New Zealand has also directed the removal of infested oak trees at one of the sites.
The beetle is native to tropical and subtropical East Asia. It has been found in many areas in the world, including Africa, the USA, Central America, Europe, some Pacific Islands, and most recently in Queensland.
Anyone who believes they have seen the granulate ambrosia beetle or any sign of frass on trees should take a photo and call Biosecurity New Zealand's exotic pests and diseases hotline on 0800 80 99 66.
Fact sheet about the beetle [PDF, 427 KB]