The varroa “destructor” mite has spread across the globe in the past 50 years, decimating bee populations everywhere, and now it is in Australia.
Key points:
- New research challenges the thinking on how to control varroa mites
- The mites are feeding on bees’ fatty liver tissue, not their blood
- A US laboratory is looking for better ways to control and perhaps kill the pest
Could new research in the United States help to stop the spread?
For years scientists and beekeepers thought the varroa mite attached itself to bees to suck their blood.
But a young researcher from Colorado, Samuel Ramsay, conducted PhD research that showed they are actually liquefying the bee’s fatty liver tissue and sucking it out.
The research shows they focus on the underbelly of the bees to access the liver.
“When these mites feed on the bees, they release a huge amount of saliva,” Professor Ramsay said.
“The saliva is what’s liquefying it [the liver], and so even though they can’t eat all of it, they destroy a big chunk of it when they feed.”
Other weird facts about varroa
It’s not the only finding Professor Ramsay has made as he looks deep into the life cycle and the anatomy of the mite.
The varroa have a very unusual breathing system.
“They have appendages on their shoulders they can use like snorkels, so if they fall into a shallow amount of fluid, they can stick them out and still breath.”
The mites are also able to hold their breath for long periods.
That is important for beekeepers because varroa mites may be surviving fumigation because of it.
“If the mites are able to hold their breath for long periods of time they may be able to escape some mechanisms of the treatments,” Professor Ramsay said.
Professor Ramsay describes varroa mites as very successful, invasive species with a unique breeding system which allows them to establish a new colony with just one mite.
They climb into a cell with a juvenile bee, and produce two eggs, one male and one female.
They mate and when the cell is uncapped and the bee escapes, the female mite is already pregnant and ready to reproduce.
‘Dreams crushed’
Authorities in NSW have held varroa at bay by launching the state’s biggest biosecurity response ever, locking down beekeepers, halting trade with other states, torching hives and killing millions of bees.
Bianca Giggins, beekeeper and varroa coordinator for the Australian Honey Bee Council, had hives in Newcastle, just a short distance from where varroa mites were first detected in New South Wales.
“It was a crazy time, when varroa first arrived and we were all working together very hard to get our head around what was happening,” she said.
She regards it as one of the most stressful times in her life.
“This has definitely crushed a few dreams, watching people around me have difficulty accepting the loss of their colonies,” Ms Giggins said.
Is eradication still possible?
The industry is pushing ahead with a strategy to eradicate the mite, but Professor Ramsay warns that will be difficult.
“You guys are the largest land mass to keep varroa out since the 1950s and it’s quite remarkable that you’ve been able to shift to controlling the mite instead of eradication,” he said.
“When it is officially established in the environment … it is unlikely to be eradicated and it would be a worthwhile endeavour to transition to management.”
Professor Ramsay, who his own laboratory in Colorado, is searching for a targeted chemical solution.
“A lot of the chemicals that are available for management of varroa are broad spectrum … so a dosage that’s slightly too high can kill the big bug we love: the honey bee,” he said.
There is one other possibility for controlling the mites, based on a discovery Professor Ramsay has made that they extract egg yoke proteins from the bees.
“We’re trying to disrupt their ability to move those proteins into their eggs,” he said.
And while Professor Ramsay continues his search, apiarists such as Queensland bee breeder Joanna Read hope he succeeds.
She works for NT Bees and spends 11 months of the year travelling with her bees to pollinate crops all over Australia.
“Maybe he’s able to find something that we can feed the bees that feed the varroa which then kills it,” she said.
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