Fresh cases of Varroa mite infestation in eastern NSW have prompted mandatory monitoring of beehives in Sydney for the first time since the outbreak began.
The potentially devastating mite was detected in six new hives across four locations including Mooney Mooney on the Central Coast, directly north of Sydney, authorities revealed on Tuesday.
It takes the total number of infested premises to 137.
An eradication zone, within which all beehives must be destroyed, now applies to Sydney's northernmost tip of Palm Beach, according to a map on the Department of Primary Industries website.
New rules also apply to any hives within a broadened surveillance zone, where officials will monitor and conduct inspections to reduce spread.
The new surveillance zone reaches as far south as Hornsby in Sydney's north, and extends to Long Reef on the coast.
Other infestations were detected in Clarence Town, Mitchell's Flat and Booral, which are all in the vicinity of Newcastle where the original outbreak was detected in June last year.
The department's Varroa mite response state co-ordinator Chris Anderson said the new sites have low mite loads, suggesting they are very recent infestations.
"The recent detection on the Central Coast, however, has meant DPI is now concentrating its Varroa response surveillance activities into the northern suburbs of Sydney, to ensure the infestation is localised and that there is no mite population in the area," Dr Anderson said.
"DPI has also had to extend the eradication (red) zone west of Stanhope, and west of Bulahdelah, following the new detections on the mid-north coast."
Earlier this year, other states and territories reopened to bees from the majority of NSW after most of the state was declared free of Varroa mites.
"Changes in the number of infected premises are expected at this stage in the response, however what is encouraging is that these mites are being found quickly," Dr Anderson said.
"We know that this is a difficult time for impacted beekeepers, but controlling and eradicating this destructive mite is critically important to NSW and Australia."