Mite could indirectly threaten native bees

Tracey Ferrier |

Native bees and plants could suffer an indirect hit from the varroa mite if it gets away in Australia, an expert warns.

Biosecurity officials have imposed a strict ban on the movement of bees and hives in NSW after an outbreak of the parasite near the Port of Newcastle.

The discovery has prompted the destruction of hives in an effort to stamp out the invader, which feeds on the blood of adult and larval honey bees and can kill colonies.

Native bees are not afflicted by the mites but that doesn’t mean they’re out of danger, University of Queensland bee researcher Tobias Smith says.

He says any widespread outbreak could put native bees at greater risk of viruses.

“If you think about mosquitoes and humans, when they bite us they can leave something nasty behind. It’s the same with varroa mites which can transfer viruses to honey bees through their bite,” he says.

“We know that when bees visit flowers they can leave behind viruses and pathogens on flowers that other bees or other pollinators can get.

“There’s evidence from other parts of the world that do have varroa mite that some of these viruses from honey bees can get passed onto various native bee species too.”

Native plants could also suffer if the mite establishes itself and takes a heavy toll on native bees.

“Introduced honey bees do have the potential to pollinate some native plants but not all,” Dr Smith says.

“Some flowers are just not attractive to European honey bees, but it can also be about the mechanics of pollination.

“We have lots of plants in Australia that need to be shaken to be pollinated and lots of our native bees shake their bodies when they pollinate. European honey bees can’t do that.”

John Roberts is a CSIRO expert on honey bee pathogens and says it’s yet to be determined if the mites found in NSW have one particularly nasty virus called deformed wing virus, which does as the name suggests.

“There are several bee viruses that get spread very well by varroa mites and become part of the problem for European honey bees,” Dr Roberts says.

“When those virus levels get high in colonies, they start to spill over into the native bee populations, and other pollinators potentially. That’s been observed at different places around the world.

“It’s still a little uncertain, when these viruses do spill over, whether they have much of an impact or not.”

He says that any spread of the varroa mite without problematic viruses could actually be a leg up for native bees.

“It will reduce the levels of feral European honey bees in the environment, and the varroa mite is not able to be a parasite of the native bees.”

Tests are underway to identify any viruses carried by the mites found in NSW.