Researcher carries out post-mortem on Varroa mites
December 3, 2012
From: Australian Broadcasting Corp.
By Kim Honan
The researcher who named the species of Varroa mite, that’s decimated bee populations around the world, says it’s only a matter of time before the pest invades Australia.
Twelve years ago, bee pathologist Dr Denis Anderson discovered that although there were many different Varroa mites on Asian honey bees, the one switching onto European honey bees and causing damage to colonies was a species new to science, and he aptly called it Varroa destructor.
The CSIRO research fellow says Australia is in a good position to research alternatives to chemicals to control the mite.
“Things like looking at the reasons why the majority of the Varroa mites are actually harmless to the European honey bees,” he said.
“We know that the reason for that is that those female mites can’t recognise a particular signal on the European honey bee that tells them to reproduce.
“If you could find that signal and look at what it does and how it operates there might be alternate ways of controlling the mite available.”
Dr Anderson says honey bee industries in other countries have had to rely on the use of acaricides to control Varroa mite.
“Mites are what we call acarids and they respond to insecticides and acaricides are a form of insecticides,” he said.
“But they’re given at very low levels, because mites are small and those small levels of insecticides in this case don’t affect the bees but they will kill the mites.
“But the mites, like with any chemical regime that you’re using, will develop a resistance which they’ve done here to many of the chemicals that’ve been produced and then you need another chemical and then you end up getting on what we call the chemical treadmill.”
Last week, a swarm of 2,000 Asian honey bees, carrying more than 150 Varroa mites, were detected and destroyed on a bulk fuel carrier in Sydney.
Dr Anderson has been conducting a post-mortem examination on the bees and expects to have the full results by the end of the week.
“At the moment, just from morphology, we’re able to determine that the mites are Varroa jacobsoni, a particular species of Varroa mite,” he said.
“We haven’t been able to type the mites just yet, it’s just going to take a little bit longer from DNA analysis and we’ll be able to determine where those mites come from.”
But Dr Anderson says that generally the Varroa jacobsoni mite had been harmless to European honey bees until a couple of years ago.
“We did find one particular population of the mite managed to switch host to the European honey bee in Papua New Guinea,” he said.
“Prior to that, all Varroa jacobsoni were harmless principally because they spread onto them if they’re living side by side, but the female mite’s unable to lay eggs or produce offspring on the European honey bees so they just can’t exist there, whereas the Varroa destructor are a little bit different from that.
“So the fact that a mite that was previously harmless on that bee has developed a pathogenic trait is of major concern.
“But the chances of that mite that turned pathogenic in Papua New Guinea actually getting here on a swarm of Asian honey bees from that region look to be fairly small, because it now looks like the population that did turn pathogenic in Papua New Guinea is restricted to the European honey bees.
“In other words, now that it’s made the change and able to switch onto the European honey bee, it cannot now go back and reproduce on its original host, the Asian honey bee.”
The results from the bee autopsy will be given to the Department of Agriculture, Fisheries and Forestry to decide what further action will be taken.
“It’s looking at the moment that the autopsy will tell us that these bees are Asian, they were on a boat that we think orientated from the South East Asian area, the bees were carrying mites, those mites we’re 99 per cent sure that they’re Varroa jacobsoni, Dr Anderson said.
“I don’t think the government will do a great deal.
“The bees have been killed on the boat. Even if some have the mites had come in contact with the European honey bee and got back onto land, they probably almost certainly won’t exist there, that they would peter out.”
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