More beehives will need to be destroyed in NSW after another infestation of varroa mite was detected outside the initial eradication zone.
The mite was discovered in a hive at a property near Cessnock, outside the current "red zone" which encompasses Newcastle and surrounding areas.
In response, the Department of Primary Industries on Thursday expanded the area in which hives are required to be destroyed in order to stop the spread of the mite.
"The detection was kind of just outside an existing red zone so it pushes that zone out by another 10 kilometres," DPI spokesman Mark O'Brien told AAP.
"But it's obviously significant in the context of the response."
An extensive tracing effort is ongoing involving the testing of 85,000 hives so far, which Mr O'Brien described as similar to COVID-19 contact tracing.
"They identify an infected property and then they interview the property owner and find out where all the hives have been in the last 24 months," he said.
"Just like COVID when you're contact tracing of a person infected at the pub and you go back and interview all their friends, it's the same thing."
Australia is the only major honey-producing country that is largely free of varroa mite, considered the most serious pest affecting bees worldwide.
"NSW DPI has put significant measures in place to arrest the spread of the threat beyond the perimeters of the eradication zones," NSW DPI Chief Plant Protection Officer Satendra Kumar said.
"The cooperation of industry and the community is vital in helping the response to achieve the goal of eradication."