Honey Bees and the Varroa Mite with Dr. David Peck (027)

Honey Bees and the Varroa Mite with Dr. David Peck (027)

[music]

Introduction: Welcome to  2 Million Blossoms - The Podcast, with host, Dr. Kirsten Traynor.  2 Million Blossoms is dedicated to protecting all pollinators from the solitary bee, to colorful butterflies, to feisty hummingbirds, and of course, the honey bee. We bring you informative guest to awaken your understanding of the vast diversity of pollinating insects and animals worldwide. Because the more we know about pollinators, the better we can provide their habitats and protect them from disappearing forever, so sit back and listen, as Kirsten and her guest share in the passion they feel for all pollinators.

Dr. Kirsten Traynor: Welcome to  2 Million Blossoms, a podcast on protecting our pollinators. I'm your host Kirsten Traynor, director of the State Institute for Bee Research at the University of Hohenheim in Stuttgart, Germany. I fell into the incredibly diverse world of pollinators way back in 2001, when I planted wildflowers in my garden, and wanted to ensure they set seeds.

Today, I've invited David Peck, a bee scientist in charge of education at Betterbee onto the show, to chat with me about bees and varroa. I had seen David's work long before I ever met him in person. His video of a varroa mite jumping onto a honey bee when it visits a flower blew my mind. The speed with which varroa climbs up the bee's leg is astounding. Never underestimate a parasite. David, welcome to the show.

Dr. David Peck: Thank you for having me, Kirsten. It's a pleasure to be here.

Kirsten: I'm super excited to chat with you. We had talked a little bit while I was at ABRC out in New Orleans. It was nice to meet you in person. How did you first get into honey bee research?

David: I sort of blundered into honey the research, I guess. Since I was a little kid, I've always been fascinated by animals, and I wanted to be an animal behaviorist for a very long time. When I was getting my bachelor's degree at Tufts in Boston, I had a professor named Phil Starks who had a PhD in wasp behavior and honey bee behavior, and he'd studied all sorts of things. He's a very interesting guy doing interesting work. He lit a fire in me about all of these cool things, and he also let me come out and visit his beehives and help him-- I think we pulled tiny supers that day or something like that, so I got a little bit of a taste for it.

I applied to work in the same program where he'd gotten his PhD among-- One of his mentors was Professor Tom Seeley at Cornell. I applied to work with Tom, and Tom said, "You're a very nice fellow, I like that you're an Eagle Scout just like me, but unfortunately, I've just taken another student and I don't like to double stack students because then I can't give anyone the appropriate attention," so he decided to option not to work with me, and I did some other work. I studied ticks, and Lyme disease, and I actually studied chlamydia in mice. I've always been interested in diseases and parasites and stuff like that.

Then the honey bee work, finally, a few years down the road, I'd done that other work on those other parasites and diseases. Tom was eager to study something to do with the varroa mites and the Arnot Forest bees that he had been studying and publishing about. What he was looking for was a parasitologist who was interested in bees and evolution and behavior. Luckily, I was looking for a project that didn't involve killing quite so many baby lab mice, and so I finally bullied my way into the lab and the rest is history. I've been able to study varroa and their behavior, and honey bees and their behavior, and have been thrilled to finally get the opportunity to do it.

Kirsten: That sounds like a great story. Varroa mites are extremely well-adapted parasites, and you've worked with them up close and personal. What has surprised you most about their behavior in your studies?

David: The first thing, and this is something that any beekeeper can experience, is when you get a varroa mite separated from a bee, you can either knock her off or you can use a sugar shake, and then clean her off with some water and dry her off with a paper towel. Once you have that varroa mite running around and you really take a good look at her, it is surprising how quickly they can move and how good they are at navigating their landscape, which is normally either the bodies of honey bees or the comb that they run around on.

I think that that was the first inkling I had that this thing isn't just a little red lump that sits on bees and makes them sick, this is an animal, and this animal is doing all sorts of interesting, complicated things. I think actually the work that I had already done on ticks and Lyme disease helped me be a little more open to the possibility that varroa mites were interesting creatures doing interesting stuff. Because ticks seem boring, they seem like they just sit in the grass all day waiting for someone to brush past, but they actually have some pretty sophisticated behaviors when you look closely at what it is that they get up to over the course of a day, a week, a month, or a year.

Kirsten: Okay. In your video, it always seems like varroa mites are pole jumping up the leg of a honey bee--

David: Yes. That video that we shot of the varroa mite on the flower jumping onto the bee is a fun one. To use the technical term in science, it was the sexiest of the videos that we were able to shoot.

Kirsten: [chuckles]

David: There were other videos where the varroa mite boringly got onto the bee. They were very fast, they were very good at it, but it wasn't quite as dramatic as what we got on camera in that one shot. It does look like the varroa mite is leaping onto the bee. It's still not totally clear to me whether a varroa mite can jump or if they are just stretching their legs out and catching a bee hair, and getting lucky and climbing onto the next body segment, but it is amazing to see that. That didn't surprise me at all, actually.

You opened this interview with never underestimate a parasite, which is sort of my motto for varroa and for parasites in general. I started saying that because I proposed that experiment, putting mites onto flowers and then seeing if bees could jump on, or mites could jump onto bees that were foraging on those flowers to Tom. Tom is a distinguished bee scientist. He had been studying and working with and managing varroa for years as well. He said, "I really don't think they can do that. I doubt that they can do that. It doesn't seem likely that a varroa mite could do all of the sophisticated acrobatics that are needed in the brief time that a bee is visiting a flower." I said, "Why don't we just try it?" He's a good scientist, so he was open to being proved wrong.

We went up there and set up the experiment. I think we got there in the afternoon. We only had a time for a few trials that evening, and we did it. Tom was just flabbergasted. He was really surprised by varroa, in a way that I wasn't surprised because I knew that they had something cool in them. That was when I think he went from thinking that he was going to have a nice relaxing trip to the woods, and I was going to do a piddly little project that would fail, and he said, "Wow, this is actually worth my time. I'm going to invest some effort into helping to make sure that we get lots and lots of observations of these mites."

Kirsten: You were working with actual flowers? Setting out mites? Can you describe this scenario?

David: The basic study was that we took a colony of bees that we knew had pretty high mites up to the Cranberry Lake Field Station in the Adirondacks. There were no other bees around, there was no other forage around. We set out a sugar-water feeder to get those bees foraging only maybe 50 feet away from the hive. It was a pretty easy foraging trip. Then once we knew that the foragers would be coming roughly to that spot, we took individual flowers, we took varroa mites that we had sugar shaken off of the bees and then dried off and kept in a nice humid little box until it was ready for showtime. I would set one onto a flower.

Then the question was not, are bees and varroa mites using flowers as launchpads for infestation of other colonies? The question was simply, if a varroa mite is on a flower, a thing that we know can happen on occasion, can that varroa mite, are they even capable of getting onto a honey bee, and then clinging to that bee, and riding that bee back home? What we demonstrated very clearly is they absolutely can do that, that a bee visiting one of those little flowers, those daisies or those acinaceous that we put out there. No matter what flower we tried, I think we tried three different species, the mites that we put on those flowers wound up almost universally getting onto a bee and then riding that bee back to her hive.

Kirsten: I've watched varroa mites emerge on newly emerged brood when I was having to pick off individual mites off bees, it is amazing how quickly they can sense where they want to go. If you had any cell you were opening with broods, they instantly ducked in there. Why do you think varroa continue to cause such problems for managed colonies, even though now we've had these decades of coexistence? Which evolutionary is still a short time but--

David: Yes. I guess that's always the place to start, is in the evolutionary sense, these mites have been on bees for what? Maybe in the areas that were first infested, the Western honey bees, these varroa had been there for a hundred years, let's say. If we figure that a colony might swarm and replace their queen once a year, then under natural circumstances or even under a lot of beekeeper management, that's maybe a hundred generations of bees. That's enough time for bees to change, for bees to develop some resistance traits and we have seen that, but it's not really enough time for a parasite-host arms race to completely play itself out.

The other disadvantage that our bees have is that the varroa mites didn't just come out of the ether. They weren't mites that were eating pollen happily and peacefully, and then they suddenly decided to be parasites, so the mites and the bees are evolving in step with each other. These are parasites that have been living on Asian honey bee species for millions of years, and so they've got a lot of generations in which they've built up an arsenal of weapons that they can use against the Asian honey bee that has also built up their arsenal of weapons.

These supercharged, super powerful, super well-equipped parasites leapt into our bees, and our bees were ignorant rubes who had no idea what was going on. I think it's hard for someone who doesn't think about parasite-host co-evolution on these timescales to really internalize just how horrifying it was for our bees to meet this super competent, super well-equipped honey bee parasite that those particular bees, the bees that we all keep around the world just had no context for and had no adaptations to help against.

I think the other problem is that for a long time, beekeepers looked at varroa as a problem that you just needed to real quick smash down, hit it with a hammer, squish it, get it out of your way, and don't think about it anymore. The strategy was, "Let's just see if we can breed the bees really fast to be completely mite resistant," and we failed at that. We know that we failed at that.

At the same time, they said, "Let's just pick a chemical that we can put into the hive. It won't kill bees, it will kill mites, and that's going to solve our problems." We had that with tau-fluvalinate, with Apistan Strips, and it worked until it didn't, until the mites were resistant. Then people said, "That's fine. We'll just use Kumulus and we'll use the Kumulus and that'll kill all the mites and not the bees," and it worked until the mites developed resistance.

Now we're looking at maybe, if not the same story, a story that has some similar elements in Amitraz, but we've also got all of these other miticides that have come online, and folks are increasingly seeing, "It's not that I need to just pick one chemical, kill all the mites, and then I won't have to think about them anymore." What we've found is that an integrated pest management framework is the best way for us to manage these things. It's about having partially-resistant bees. It's about managing our bees in such a way that they wind up being less susceptible to the worst effects of the mites. It's about using different treatments at different times when appropriate. It's all of those different steps working together that leads to beekeepers who successfully manage varroa, who don't stress about varroa. It's just a thing we have to deal with.

I think that desire to just say, "Ooh, a yucky parasite, let's not learn anything about it, let's just kill it and be done with it," is probably the shortcoming that a lot of beekeepers suffer.

Kirsten: Yes, I think every beekeeper needs a mite management strategy. You spoke earlier about the generations and the honey bee, and of course, the varroa mites, because their reproductive cycle is only in the capped brood stage, it's much, much faster, and they have many more chances then to evolve mechanisms to evade whatever we put in our hives.

David: Exactly.

[music]

Betterbee: Are you an experienced beekeeper, eager to try something new? Try making comb honey. Betterbee has you covered. Our range of ready-to-use systems, including Hogg Halfcomb and Ross Rounds, makes it a breeze to get started. Or, craft your own cut comb right in your existing frames. With Betterbee's expert guidance, you'll soon be harvesting delicious comb honey. Explore the options at betterbee.com/combhoney.

Kirsten: Beekeepers often worry that treatment-free beekeepers in their neighborhoods may be causing problems through varroa mite drift and robbing. You've actually looked at this in depth. What happens when a colony is collapsing from mites? Where do they go?

David: This was a question that I was really excited to study because it was a combination of a bunch of my interests. I'm interested in the parasites, the varroa mites, but I'm also interested in when honey bees acts like parasites. When one honey bee colony sees a weak honey bee colony next door and says, "Ooh, we should steal all of their honey because they don't have enough guards to repel us."

I was interested in how the bees acting like parasites of each other would lead to the spread of these parasitic mites. We set up this experiment, which was very satisfying to do, where we bred a whole bunch of varroa mites in one colony or one group of colonies that were all headed by Cordovan bees. Very, very yellow, yellow, yellow queens that made very, very yellow, yellow, yellow offspring. Then, we put them into an apiary array where we had colonies at different distances, and they all had very, very dark Carniolan queens, and so they were making very, very dark bees.

What that meant was that I could go look at one of these yellow bee colonies, and if I saw a black bee going in there, I could say, "Aha, you weren't born here. You either drifted in or you're a robber coming in to seal food." Likewise, I could look in the black bee colonies, and if I saw a yellow bee, I knew that she didn't belong there. That gave me an opportunity to ask this pretty basic question. We know that if your colony has a lot of varroa mites and then starts to die, those varroa mites, if given their druthers, would rather get into a healthy colony and start ruining their day as well.

We also know that a varroa mite is not going to pack up her bag and hike 200 yards down the edge of the forest to get to your next hive, so clearly the way these mites are spreading is by being carried by bees. What I needed to do was figure out when bees from one colony go into the wrong colony, and that was going to be either drift or robbing.

What we found in that study in upstate New York in the fall or the summer and the fall, is that drift was happening. Right from the moment we set the bees out in the apiary, there were bees of one color showing up in colonies of the other color, so it was clear that there was some amount of drift taking place. That was mostly happening when they were all packed closely together. When the colonies were about one meter apart from each other. The colonies that were 50 meters or 300 meters away, they were much less likely to have a jump in their mite population, and it was much harder to spot a yellow bee going into one of those dark bee colonies.

However, we also saw that as the season wore on, and in our neck of the woods at the end of the goldenrod flow, when the only remaining goldenrod smell that the foragers could find was in the ripening goldenrod honey in other colonies, a lot of those bees were very eager to go in and rob the weak colonies that were dying and collapsing from varroa infestation. We saw a huge number of dark robbers from all of the colonies, no matter how far away, flying into the weak yellow colonies, stealing all of their honey, but also at the same time, apparently picking up a large number of varroa because they had a very dramatic varroa spike in each of those dark bee colonies.

That led us to conclude that both drift and robbing are important, but that, especially over a longer distance, like the distance from my apiary to your apiary, the robbing in our case seemed to be more important for the bulk spread of a bunch of varroa mites. At the same time, I was doing that, Randy Oliver in California was doing his own study of drift and robbing, and he found little to no robbing, but he found that his drift was actually happening over pretty long distances. His conclusion was that drift was more important. My conclusion was that in some ways, robbing is more important.

People say, "How do you guys do that? Are you in a fight with Randy because you guys reached different conclusions?" The answer is no. We've both looked at each other's data and we've both said, "Wow, that's really neat. You found something over there at that time. I found something over here at this time." What's clear is both drift and robbing can spread mites from dying colonies to healthy colonies, and we don't know enough about when exactly that happens to know which thing is necessarily going to be the predominant mechanism for mite transmission.

Kirsten: If you put that into beekeeper lingo though, if you have really strong colonies, you've done all your mite management, you've been on top of the game, you're actually at higher risk then for bringing home problems because your colonies are going to be the ones out there picking fights with the weak ones.

David: That's exactly it, is that in a beautifully perverse way, the stronger your colonies are and the weaker your neighbor's colonies are, the more likely your bees are to go out and rob the honey and also pick up the mites. From the perspective of the varroa mite, that's exactly what they want. If you were a varroa mite in a colony that you and your sisters and family had just murdered, or were in the process of murdering, which colony would you want to get into? Probably the biggest, strongest one in town. The parasite behavior has this horrifyingly elegant way of often playing out in a way that gives the parasites what they want. If I make this colony really, really sick so that they can't maintain a guard force, odds are pretty good that they're going to get robbed by all the healthy colonies nearby.

Kirsten: Great dispersal method. [chuckles]

David: [chuckles] Exactly.

Kirsten: Thank you so much. I really enjoyed chatting. The last question I ask all my guests is, if you had to pick a pollinator or a plant to represent you, what would you choose?

David: Oh, gosh, to represent me? It's not just picking my favorite, it's the one that represents me. I suppose if we had an hour, we could talk about interesting flowers and parasitic bees and all sorts of cool things like that, but I do worry that my position as the Director of Research and Education at Betterbee, would be undermined if I didn't say, I have to go with the honey bee. The cooperation, the teamwork, putting in the effort to help those around me is, I like to think, is the way I try to live my life. I think I'm going to have to go with the honey bee.

Kirsten: Very good choice. I can't knock you for that.

David: [laughs]

Kirsten: Honey bees is what got me hooked into this whole thing long, long time ago. I wish you much success at Betterbee. Thank you so much for being on the show.

David: Thank you so much for having me. It's always a pleasure. I'd be happy to come back and talk about something else some other time.

Kirsten: I will be sure to have you back on the show. Careful what you wish for.

David: [laughs]

[music]

[00:21:05] [END OF AUDIO]