On the lookout for beetle pest

Wood-boring granulate ambrosia beetle

BIOSECURITY New Zealand is asking the public to report any sign of the wood-boring granulate ambrosia beetle (pictured) that can threaten a wide range of broadleaf trees, including horticultural species like avocado.

The unwanted pest has been detected in five Auckland areas since February 20.

“This is the first time the beetle has been found in New Zealand,” an MPI spokesman said. “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 two years.”

The granulate ambrosia beetle is regarded as a serious pest overseas.

Biosecurity New Zealand was currently assessing the potential risk from the beetle to New Zealand, surveillance and incursion investigation manager Brendan Gould said.

“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 said a tell-tale sign was 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.”

Brad Siebert from New Zealand Avocado said that “avocados looked to be relatively low risk”, based on people he had talked to in the US and Australia.

“Ambrosia beetles are fungus farmers, having a symbiotic relationship with one or more fungi, which they introduce into the tree as an exclusive source of food for the adults and larvae — they never feed on the tree itself,” Mr Siebert said.

“The beetles transmit this fungi into tunnels that they excavate.”

The beetle has not been found on avocados in New Zealand, and the fungi detected in Auckland does not present a major threat to tree health.

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 on 0800 80 99 66.