Neil Livingstone, of Newcastle, in the NSW Hunter region, said he checked the six sentinel hives as a volunteer for a decade for the NSW Department of Primary Industries.

"It was taken off me because of COVID. The DPI ruled that once COVID hit, volunteers had to get out of the picture," Mr Livingstone said.

Mr Livingstone said he had been checking the hives "every four weeks".

"It used to be six-weekly checks 10 years ago. Then they brought it to monthly. I kept saying we should be doing it every two to three weeks, keeping a much closer eye on it. They could have asked us volunteers to do it on a fortnightly basis instead of a monthly basis.

"I kept on saying, gee a month's a long time. A lot can happen in a month. It's quite obvious, they got caught out."

The parasite's entry into Australia, through Newcastle, threatens the country's multi-billion dollar pollination and honey industries.

A NSW DPI statement said the sentinel hives were "checked approximately every six to eight weeks".

"The hives were inspected in January, February, April and May before the detection in June."

NSW Agriculture Minister Dugald Saunders said "biosecurity is one of my top priorities".

"Beekeepers have been working with the government through the National Bee Pest Surveillance Program to act as an early warning system. The sentinel hives at the Port of Newcastle have demonstrated just how effective our surveillance methods are in picking up potential threats," he said.

"If it weren't for the diligent monitoring of hives and catch boxes at strategic locations around our ports and airports, this incursion may have gone undetected. Thanks to the sentinel system we were able to act swiftly to set up biosecurity zones and immediately start the crucial contact tracing process."

Mick Veitch, Shadow Minister for Agriculture and Regional NSW, said a "well-funded and well-drilled biosecurity system is our frontline defence in protecting NSW's multi-billion agricultural sector". "Timing is critical when it comes to varroa mite incursions and our broader biosecurity response," Mr Veitch said, as he called for transparency.

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The varroa destructor mite was first detected at two sentinel hives in Mayfield on Wednesday, June 22. Those hives were destroyed.

The NSW government has established three biosecurity zones that cover a massive area from Forster to Sydney in a bid to eradicate the parasite. The first zone was around the Port, with subsequent zones around Bulahdelah and Calga. Millions of bees have already been euthanised within the eradication zones.

Mr Livingstone has two hives at Warabrook that have tested positive for varroa mite. The government knows about this, but has not euthanised these hives.

"They're not killing those at the moment, they're mapping hives to get an indication which direction the mites could be travelling."

Mr Livingstone has checked his other hives at Hamilton, Stockrington and Raymond Terrace and they were clear of the mite. This gives him some hope that the mite could be contained.

"Our advantage is we're in the middle of winter. Bees prefer to be warm. If this happened in September or October, they'd never contain it."

The mite threatens the $70 million honey industry and $14.2 billion pollination sector.