Lab Notes: Varroa is here but honey bees strike back
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For a long time, Australia was known for being Varroa mite free. That's the parasite that's responsible for destroying bee colonies all around the world. Then in 2022, the mite was discovered at the port of Newcastle in New South Wales. A new biosecurity zone has been established in New South Wales after the destructive Varroa mite was discovered at three properties... The pest, whose scientific name is Varroa destructor,

has since been detected in Victoria and, just last month, in hives five kilometres from the Queensland border. Now, to date, Varroa hasn't been seen this far north in New South Wales, where it's slowly spreading and causing colony collapses in wild honeybee populations. The good news in all this is that some honeybees can fight back, and they're being helped by breeders, scientists and artificial insemination on the tiniest scale.

Hi, I'm Belinda Smith and this is Lab Notes, the show that brings you the science behind new discoveries and current events. Joining me to find out how the devil you inseminate a queen bee is Dr Nadine Chapman, National Varroa Management Education and Training Coordinator and a friend to honeybees everywhere. So varroa mite, it's relatively new to Australia. What is it and what makes it so dangerous to bees?

It's an ectoparasitic mite. That just means that it's an external mite of honeybees. It feeds on the brood when they're developing. That's where it reproduces. And it also feeds on the adult bees. Right. So it literally latches on and it just sucks the life out of them?

Yes, so it feeds on their fat body, which is akin to our liver. So imagine having something the size of a side plate or dinner plate attached to your torso, sucking out your liver.

What else does the mite do? How else does it harm bees? It can also transmit viruses and these viruses are often worse than the actual feeding on the bee. They can result in the wings being deformed or them having paralysis and obviously that's going to have a big effect on a hive if a lot of the bees are unhealthy and unable to forage.

We hear the phrase colony collapse when talking about varroa. What does that actually mean? It's used to describe when basically the bees have just left and there's no bees left in the hive. And certainly one contributor to that will be varroa and the viruses that it spreads. But other things can have a role in that, such as pesticides. Music

So varroa mites hurt honeybees in a few ways. They infiltrate bee nurseries and feed on the babies. They latch onto adults and feed on them too. And spread awful diseases. All this can destroy entire colonies. Now, the varroa mite's arrival is relatively fresh here in Australia, but other countries have been battling the pest for decades. So I was curious to find out what impact the mites had had on bee populations elsewhere.

So for example, in America, they, I think last year, lost about 50% of their bee colonies over the year. And it's natural, particularly in climates that are much cooler, to have some of your bees die over winter. But what's not natural is losing that many. And then the proportion can vary each year.

But certainly it's becoming more and more of a worry and Varroa will be contributing to that, but there'll be other contributors to that as well. So in terms of Australia, Varroa was first discovered in Newcastle. Last year it was detected in Victoria and now it's very close to the border of Queensland.

How does the mite spread so far? So varroa will naturally spread through the managed and feral populations, expanding their range each year. But what's made it be able to travel so far is that we have migratory beekeeping in this country. So the beekeepers, they need to find places

food for their bees all the time. So they're looking for a good area that's got flowers in bloom and they'll take their bees there. And unfortunately, they also take varroa as well. So what can we do now that it's here? Like what steps are being taken? We do have a number of chemical treatments and there's also

some mechanical controls that beekeepers can use because I know that some beekeepers are really hoping not to use chemicals. But what we advocate is for an integrated pest management approach so that you're keeping your chemical use as low as you can if you are using chemicals.

That's because varroa mites can quickly develop resistance if you use too much of one chemical. And then we'll have one less tool in our toolbox to use against them. One type of mechanical control is what's called a brood break.

You temporarily take the queen away from her hive, so no more babies get born, and any Varroa mites in the hive eventually end up on adult bees, which can then be treated with pesticides. Of course, they can pick up more Varroa after that from possibly feral colonies in the area or if there's other managed honeybees in the area because bees will go and rob out weak colonies, for example, and then they can bring Varroa home on that colony.

The best thing is to combine a brood break with one of the chemical treatments, but it just depends on the beekeeper's ability to do that. Okay, so beekeepers have developed ways to control varroa mite, but we can't underestimate the role the bee plays in all this.

Yeah, there's some what are called naturally resistant populations around the world, mostly on islands where they've been left isolated and not had any management of them. So any susceptible colonies die and then the survivors can repopulate all of those nests as time goes on and that keeps on going until more and more of the population becomes resistant to it.

There are downsides to these naturally Varroa-resistant bees. They tend to be more aggressive and make less honey, and they're more likely to up and leave the hive and find a new home. Not ideal for beekeeping. But Australian bee breeders have already bred queen bees with specific male bees to try to create colonies that are less vulnerable to Varroa attack, but still, you know, make lots of honey.

So what does this Varroa resistance look like? It's really anything that helps keep the mites loads low. So this can be things that kill the mites or prevent them from reproducing. For example, if the bees recognise that there's something wrong in a cell because the bee is ill or it's infested by Varroa, they might open that cell and that changes the temperature and humidity and any immature mites in there will die.

They can leave it at that or they can remove that pupae. So they're also removing the varroa. So the bee nurses who tend to the developing baby bees smell the varroa and get rid of it.

And there's also signals from the brood that Varroa needs in order to commence reproduction. Baby bees emit different chemicals at various stages of development, which the mites pick up on. And if they don't get those signals, then they might not reproduce at all, or they might be delayed. And of course, when the bee emerges, if the mites are not yet mature, they will die. And then, just like monkeys or even humans...

Bees help a sister out. Bees can also try to groom themselves to get Varroa off. If they're not successful, they can do a little dance to get one of their sisters to groom them and then Varroa will hopefully end up on the bottom of the colony and unable to get up or it might suffer damage to its body or legs, which will reduce its lifespan. And obviously not having Varroa

four different dinner-sized plates feeding on your liver while you are developing would mean that you're going to come out much healthier. So fewer mites, fewer viruses, happier bees. Yes.

So these antiviral behaviours are a good sign, but for bee breeders who want to make sure these traits get passed on to the next generation of bees, it's a slow process. The bee breeders will be needing to test these traits in a lot of colonies and then selecting the best ones and then they...

raise queens from the best colonies and also drones. And this is where artificial insemination can be super helpful, giving breeders way more control over whose genes get passed on. You're collecting the drones straight from the colonies that you want to use and using that to artificially inseminate the queen. How do you extract sperm from a bee? Um,

You just squeeze. I guess you have to squeeze in a special way. They kind of like their head to be squeezed a bit. Okay. The head, the head head. Not their penis head. No, no, their head. Okay. Yes. And I doubt you're going to use this, but I'll tell you anyway. A drone's penis is a third of its body weight.

What? How could we not use that? As my university professor used to say, they are penises with wings. They do no work in their life. That's their one job. Okay, so when I think of artificial insemination, I think of being on a farm. I've seen a cow getting artificially inseminated. I mean, for an insect, it must be an incredibly delicate operation. Yes. So the semen is collected in a syringe and

So you've got that ready and then you get your virgin queen. She gets put in a little harness and given some carbon dioxide to knock her out so she won't move around because if she moves, she'll get damaged. And then working under a microscope, they use some small hooks to open her reproductive tract and then insert that needle and inseminate her.

And then, of course, because she's the queen, she's the one that lays the eggs and uses that sperm with, you know, hopefully those resistant gene variants to create a colony that has those behaviours and emits the signals that can keep the mites down. Yes. Bee insemination was not a rabbit hole I ever thought I'd go down. And it shows what an enormous job beekeepers and honey producers have now Varroa's here.

But the fact that Australia kept Varroa out for so long means we have more options to control it. Australia is so lucky. I know that's hard to hear, but thinking about it relatively, we've got quite a number of different treatment options, both chemical and non-chemical, that we can use that no other country has had as many options when they first got Varroa. As someone who works in the National Varroa Management Team...

and a bee researcher yourself. How worried are you about varroa mites in Australia? I was absolutely devastated when I first heard that it was here. But I think the important thing to remember is that every nation that has varroa still has a beekeeping industry. So we can also adapt to

Yes, it's scary. There's new techniques to learn. We've never had to worry about keeping records of chemical treatments before, but we can all adapt and we will find a way forward. But the golden era of beekeeping in Australia does seem to be over. Nadine, thank you so very much for these insights into where we're at with varroa mites and what the future might hold. It's been really great to talk to you. Thank you.

Thanks for listening to Lab Notes, where every week we bring you the science behind new discoveries and current events. I'm Belinda Smith. This episode was produced on the lands of the Wurundjeri and Mojok Noongar people. The show was produced by Fiona Pepper and mixed by Kerry Dell. And we love to hear from you. Email us, labnotes at abc.net.au. Catch you next week.

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