An avocado tree-loving beetle, regarded as a serious pest overseas, has been discovered in Auckland, local media TVNZ reported.

The wood-boring granulate ambrosia beetle has been detected in four Auckland areas since late February, according to Biosecurity New Zealand.

The beetle is known to feed on a wide range of broadleaf trees, including horticultural species such as avocado, and can spread fungal diseases.

The discovery of the beetle is the first of its kind in New Zealand, but Biosecurity NZ said early evidence suggested it may have been in the country for at least two years.

Biosecurity NZ surveillance and incursion manager Brendon Gould said the potential risk of the beetle being in the country was being assessed.

"We need to know if New Zealand has a wider population, which is why we are asking the public to report any possible sightings."

Gould said the beetle lives under bark, making it difficult to detect.

However, he said 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.