Over six million bees were euthanised across Australia's east coast this week, an official said Wednesday, in an attempt to eliminate a devastating parasite which has continued to spread despite a lockdown of hives.

600 hives have been destroyed since the "Varroa destructor" mite was detected, with each containing anywhere between 10,000 and 30,000 bees, New South Wales agriculture minister Dugald Saunders said.

"It's a lot of bees," he said, noting the number was likely to grow.

Bee ecologist Jay Iwasaki from the University of Adelaide described the tiny red-brown Varroa mites as "a little vampire" that feeds on larval honey bees.

They can also spread "some very serious viruses" through honey bee colonies, which are not native to Australia but vital to the country's agriculture industry.

"Even if this incursion is snuffed out, the global nature of trade will continually bring infested honey bees to Australia," Iwasaki said.

Australia is the only major honey-producing country where the mite is not already endemic, prompting a biosecurity lockdown of hives after it was detected at the country's border earlier this week.

Hives within a 10-kilometre radius of four varroa mite zones must be destroyed, while keepers elsewhere in New South Wales will not be able to move hives, bees, honey or comb until further notice. 

The state's Department of Primary Industries said the measures aimed at "ensuring we eradicate the parasite". 

Iwasaki noted that if the mite does get a foothold, there may be an unexpected beneficiary - native bee populations, which are not affected by the pest.

Native bees compete with feral honey bees for scarce resources, an issue exacerbated by habitat loss, including land clearing and climate disasters.