60 Dr. Bob Peterson – Alfalfa leafcutting bees and mosquitos.


Speaker 1: From the Oregon State University Extension Service, this is Pollination, a podcast that tells the stories of researchers, land managers, and concerned citizens making bold strides to improve the health of pollinators. I'm your host, Dr. Adoni Melopoulos, assistant professor in pollinator health in the Department of Horticulture. It is a true scandal that 60 episodes in and we have not had one episode about alfalfa leaf-cutting bees. Arguably alfalfa leaf-cutting bees are one of the most important bees in North America right behind the honey bees in terms of crop pollination.

They also have a real fascinating production system that is really unlike anything else. So I thought this was a great opportunity to reach out across the Rockies to Dr. Bob Peterson, who is a professor of entomology at Montana State University. Many of you probably know Dr. Peterson. He's going to be the incoming president of the Entomological Society of America.

And he's also been really prodigious in the area of comparative risk assessment. And this is where Dr. Peterson's interest in alfalfa leaf-cutting bees comes about. His research asks the question of how risky insecticide treatments are for mosquitoes in and around alfalfa fields that have alfalfa leaf-cutting bees in them. This is a great episode for not only learning about alfalfa leaf-cutting bees but also thinking about how we calculate risk when it comes to using insecticides around bees. Hope you enjoy the episode. Welcome to Pollination Dr. Peterson. Thank you.

Thank you for having me. Now, we have shockingly not talked about alfalfa leaf-cutting bees on this show, but they are one of the most important pollinators in the U.S. And I know they've been hard at work this month pollinating the nation's alfalfa seed crop. Can you give us a brief sketch of the management of leaf-cutting bees?

Speaker 2: Yeah, leaf-cutting bees are in a family with many thousands of species. And as you said, mostly we're talking about alfalfa leaf-cutting bees, but also they have some close relatives like the mason bees.

They're all important in pollination, not just of alfalfa, but other crops as well. And so they're solitary bees, but interestingly, they don't mind being close to each other. And so that behavior lends itself to people being able to manage their activities and cultivate these bees and sell these bees. And of course, the pollination leads to fruits, vegetables, and alfalfa seeds, as we'll talk about. Alfalfa leaf-cutting bees are the most important and most intensively managed of this kind of leaf-cutting bees and these solitary bees. And the alfalfa seed, I looked it up, the value of alfalfa seed that's produced is $5 billion per year.

Speaker 1: Wow, massive. When considering the seed and the associated grazing and all the alfalfa fields you see are most almost all of them are to be cut and used as livestock feed, of course. But those plants have to come from somewhere and that forage has to come from somewhere and it comes from the seed that's planted and that seed comes from the activity of alfalfa leaf-cutting bees.

And that industry is especially important in the western United States and it can't in western Canada as well. It's just ideal for producing alfalfa seed because of the dry, warm climate and the bees thrive in that environment as well. And so just in comparison, throughout the $5 billion per year industry, the Valley Bees US agriculture is about $14 billion. So we're talking about a substantial amount of value that's provided by alfalfa leaf-cutting bees. And yet I have not seen a leaf-cutting bee on anybody's t-shirts. I mean, there are no posters, save the leaf-cutting bee.

Speaker 2: And there should be. You know, we shouldn't have all this bias towards honey bees, although that's perfectly understandable. And so a little bit of a primer may be on the life history and how these bees are managed.

Speaker 1: The leaf-cutting bees spend the fall and winter in refrigerated rooms because they are managed. And yes, there are wild leaf-cutting bees and they spend the fall and winter as fully grown larvae in the environment. But if we're talking about the management of these bees and the use of these bees, they're brought in at the end of summer

Speaker 2: as fully grown larvae within each one within its leaf cell. They're called leaf-cutting bees because the bees cut leaves and make a leaf cell in which the larvae develop on pollen.

And we'll talk about that a little bit more. But about a month before alfalfa is blooming, wherever you are, whether it's Nevada, Eastern Oregon, Montana, Alberta, or Saskatchewan, the leaf cells are put or warmed up to about 85 degrees. And then that allows the larvae, the imitators to become pupae, which is the stage between the imitators and the adults. And so the adult male and female bees are put out right before emergence in nest shelters. They're really just sheds. But those sheds are filled with what are called bee boards. And those bee boards contain nest tubes. So it's kind of like, if you think about a three-dimensional pegboard, you have pegboards that you hang your tools on, they have holes. Well, just expand those in terms of depth about four inches, five inches, and they're tubes instead of holes.

Okay. That's what a bee board looks like for alfalfa leaf-cutting bees. And so you put all these leaf cells out right before adult emergence. The adult bees emerge. And when they do emerge, the females mate pretty quickly. The males emerge right before the females and wait for the females. Females emerge. The males accost them and mate with them. And then the real work begins because the males have done their job.

They're not needed anymore. And the females then go out, they're right next to fields and infants. And a lot of people might not realize this, but when they're driving on the highways and they look at an alfalfa field, it has what looks like little metal sheds or little wooden sheds.

Speaker 1: Yeah, little bus stops in the middle of the field. In the middle of the field, that's where hundreds and hundreds and hundreds of thousands of leaf-cutting bees are doing their job.

So the females start right away. They begin cutting leaf pieces and leaf-cutting doesn't hurt the plants at all because they just don't take any leaf material. They gather pollen and nectar, both. And as a result of that, they're pollinating the alfalfa in the process, much more efficiently than honeybees. And that's why they're much desired for alfalfa seed production. Why is that? You know, you can get alfalfa, honey, why are honeybees not a good pollinator for this crop?

Speaker 2: Honeybees like to cheat because they don't like being hit on the head when the flower trips and they find ways to cheat and get the nectar and pollen without pollinating the plant and pollinating the flower. And alfalfa leaf-cutting bees, don't have any problem at all doing that. They don't mind getting hit on the head by this stamina column.

It's all technical and everything. But and so they're smaller. They're only about, I didn't mention this, but they're only about one-third the size of a honeybee.

So they're about the size of a housefly. And so they have no problem. Alfalfa loves them.

They love alfalfa. And so while the female is pollinating, she's also gathering pollen and nectar. She goes back to the nest tubes after she creates a leaf cell, a cell made of leaves from the cut leaves that she gathers. She begins to form a pollen provision or a pollen ball. And that's mainly pollen, but also with nectar.

So it's this gooey, sweet mass. And when she's done creating that pollen ball, she will lay one egg on the pollen ball. OK. And then seal the leaf cell. This leaf cell is contained unit made of leaves with a big pollen provision, a pollen ball inside one egg that hatches into an alfalfa leaf-cutting bee immature or larva. OK. That larva then feeds on the pollen ball until it's gone, essentially.

So a female does that numerous times. So it's nothing like a honeybee hive with a queen and workers. It's each female is kind of her queen, so to speak. And she has a leaf cell that she does numerous times. So she makes numerous leaf cells.

Speaker 1: So she's kind of like her own queen and her worker because she's got to do all the everything. Exactly.

Speaker 2: Yeah. No casts. They're not truly they're not truly social. They are solitary bees. OK. And so the the female will make about it depends, but basically can make 25 to 50 of of these leaf cells. So they'll have 50 progeny, OK, 50

Speaker 1: imitiers, which is sitting on this pegboard.

Speaker 2: They're just sitting in this pegboard. And because they don't mind they're gregarious, they don't mind being next to each other, that you'll have thousands and thousands and thousands of females doing this. So you're producing hundreds of thousands of individuals that and this is why they can be managed and you can make you can make money off of this enterprise as well.

OK. So then what happens with the larvae? They hatch, as I mentioned, they feed on that pollen ball, that pollen provision over about the next three to four weeks. So this is all happening like where I am in Montana. They haven't put the bees out yet, but around July 4th, they put the bees out. Now, if it's Nevada or Utah, they're already out. But it's timed where they're put out, where the alfalfa is blooming, of course. So you don't want to put it out as soon as the alfalfa greens up because there are no flowers.

So it has to be put out. These bees are put out right before you have kind of full bloom in the field. And so it only it only takes about three weeks, three to four weeks for the larvae to develop completely.

And at the end of summer, then around August, here, it's the end of August, but other places might be a little earlier. Those bee boards with those filled nest tubes, they have all these nest cells or these leaf cells lined up in this pegboard kind of thing. They're brought inside and then the leaf cells are punched out of the boards and held for the winter. So they're punched out of the boards and held in these large, almost like garbage cans. So you've got you've got thousands and thousands of these old leaf cells. And some are strung together. There might be three or four leaf cells stuck together, but others are just individual.

Speaker 1: You know, I think a lot of our listeners have worked. There's a lot of interest in mason bees. And I don't think they quite realize the level of mechanization, like all the kind of handwork that you do with mason bees. This is all done by machinery.

Speaker 2: Yeah, it's by machinery. And the technology continues to evolve. They've got this kind of these pegboard, these bee boards that are now made of like styrofoam. However, it wasn't too long ago that they were made out of wood and it was much harder to get these leaf cells out.

And now it's much more kind of mechanized, as you said. And so those are punched out and they're held for the winter in these rooms, these cold rooms. And the bee producers then as the next spring comes around, will sell the leaf cells by the gallon to alpha seed producers.

Speaker 1: A gallon of leaf headers, please. Take a gallon and so on. And yeah, and it's amazing. It takes tens of thousands of bees per hectare or acre, if you will, to produce alpha seed. So it's very costly.

But the alpha seed is very valuable as well. And so they make it work some years better than others. This is a year with low value because I think overproduction of gallons of bees. And so they're trading or selling for lower value than maybe two or three years ago. So it's, you know, it's a business.

And so there's supply and demand and everything like that. And then you've got issues with bees that have chock brood disease and bees that are tied by little tiny wasps. And so even though they don't have the same pests in terms of Varroa mites that say honey bees do, they still have pests, they still have diseases, and those things, those need to be managed and things like that. OK, that was a fantastic little primer for all of us on Alpha Leaf Cutting Bees. Thank you so much.

We really appreciate it. But I actually was really, I'm really looking forward, I was really looking forward to this conversation because you've done some fantastic work in your lab in the intersection between mosquito control, which is an extremely important public health issue, and leaf-cutting bees. Can you describe how these, you know, this leaf-cutting bee system and alfalfa seed production system can come into conflict with mosquito control?

Speaker 2: Yeah, definitely, because it can and it does. And so when you have numbers of adult mosquitoes that reach certain thresholds, so the numbers cross these predetermined thresholds, they're often managed with these public health products. And what does that mean? That basically means treating an area. And again, we're talking about adult mosquito control or management.

Treat it. We're treating an area that's really just an outdoor space with an aerosol cloud of what we call adult asides in the industry or those in the know, so to speak. It's kind of a strange term. But what it is essentially is these are insecticides that are targeted at adult mosquitoes.

So adult adults aside. OK, now these insecticides are there aren't too many that are available for adult mosquito control, and the ones that are available, unfortunately, are highly toxic to many insects, OK, including bees. So they're inherently highly toxic.

There's the conflict, right? And so you've got areas where you have, as you know, with honeybees and hives, some areas are treated for mosquitoes and also the same with leaf-cutting bees and other managed bees that are treated for adult mosquitoes. So you've got this outdoor area that's being treated, whether a truck is driving by and treating an area or an airplane or a helicopter. And so people naturally have every right to be concerned about that because these materials that are used, these treatments are are inherently highly toxic to the bees. But this is really critical to understand toxicity is not the same thing as risk. OK, risk is a consideration of both toxicity and exposure. So you can't really understand risk by just looking at inherent toxicity. It's as the old saying says, it's the dose that makes the poison. And so how much are bees exposed to these inherent sick insecticides that are used for mosquito control?

So that's really what my lab has been about, what we've been doing in terms of the research. So it's important to understand that these products, this kind of public health products, mosquito management products are applied using what's called ultra-low volume technologies. And so what does that mean? Just kind of what it implies, you use very, very, very small rates of these insecticides that are applied as very, very, very small droplets. And so and so, for example, I don't want to get too technical here, but some of these same products are used in agriculture.

OK. But in agriculture, when they're used, they're at 35 to 50 times greater rates in the environment. OK. And so with mosquitoes, then that's that's quite low compared to, say, an agricultural rate of some of these things.

Speaker 1: OK. So let me get this straight. So it's still there but you can use such a lower rate because the mosquitoes are so small and flying in the air. Is that the reason?

Speaker 2: Yeah, exactly. They're so small and they're flying. So what do these really ultra-low volume with ultra-small droplets do? They're designed to stay in the air, not for long, but stay in the air. And they're designed to land on flying female mosquitoes in the evening. And so they're not in the air environment for long. And it's this aerosol cloud, this mist, basically, that travels through the air. And as the mosquitoes, the female mosquitoes are flying and looking to feed on your blood, these droplets land on them and knock them down. And so that's that it's even though, again, they're inherently highly toxic to bees, they're really designed the application and everything about them is designed to target adult flying mosquitoes.

Speaker 1: OK. So if I get this straight, although they're highly toxic to bees, because they're applied at very low rates and also in the evening, that risk is not what you would expect given the toxicity of the product.

Speaker 2: Right, exactly. Got you. So that's where and the labels all, you know, for these products, say, you know, to not to apply in the evening and also, you know, apply according to this ultra-low volume application equipment and everything like that. And that helps limit the exposure, which therefore limits the risk. So if the risk is a combination of exposure and toxicity, like we talked about, it is for that much that some of these materials are highly toxic to these because the exposure is so low. And if you if you figure both of those or assess both of those, consider both of those, then the risk is also low.

And that's what the MyLabs research basically involves assessing the exposure and therefore the risk to leaf-cutting bees to these products. And that's and we can talk about the results and what we found and things like that. And then how to manage risk when it's appropriate here coming up. So that's that's what it's all about. And we've in my lab, we've even done research to deliberately have worst-case scenarios. Yeah. And so in other words, to apply to have exposures that that wouldn't really occur. And we've done that and even found that the risk can be quite low, even with those considerations as well.

Speaker 1: Oh, fantastic. Well, let's take a quick break, and let's come back. And I want to I want to hear more about the specific research and some of the findings. OK. Well, welcome back. We were just talking about risk and exposure and some of the technical reasons why the way mosquitoes are controlled may not necessarily lead to high exposure. But can you tell us a little bit about your work and how it can help inform vector control districts that are trying to do good work around pollinators? What do they tell them to do?

Speaker 2: Yeah, the research we do gives direct answers to those involved in both mosquito management and pollinator production and conservation. And that's really critical. I think a lot of the mosquito control districts out there want to do the right thing. They want to use the best science. They want to manage mosquito populations, which can handle effects on our health and other insect vectors as well, such as ticks and so on. But also they want to protect pollinator populations.

And so our research, the research that that's done in my lab and by some incredibly talented students and others suggests that these risks can be quite low and managed fairly easily. If you just do this, which is kind of almost common sense, you treat areas for mosquitoes in accordance with the product labels. You don't apply directly over the nest shelters or through the nest shelters. And this could apply to honeybee hives as well.

We could expand it a little bit. And then apply in the evening when the bees are not foraging, they're back in their shelters and you apply using this ultra-low volume technology. And so one thing I mentioned before was that we deliberately tried to worst-case scenarios here. So what we did in our various studies was instead of not treating or applying the materials in front of these nest shelters, we deliberately applied them in front of the nest shelters. And these are open nest shelters, not quite like honeybee hives.

So they're more open. And what we did was apply at 8 o'clock, 8.30, 9 p.m. So still kind of light out.

The bees are still a little more active than they would be after that time. And we would apply at maximum label rates or rates that probably are a little bit more than what you would see in the real world. Got you. Exposure is more. And this aerosol cloud of material is going through the nest shelters. So it's going with the prevailing winds right through the front of these nest shelters.

shelters. And I tell you, I would have predicted that the next morning, we'd see a lot of dead leaf-cutting bees in front. And we put down drop cloth and things like that in front of the nest shelter, so we wouldn't miss that. And we didn't see any dead bees in front of those nest shelters. And so that really surprised me. That was one of those, huh, I would have thought we'd have some.

Speaker 1: Yeah, you would think that some of those particles that are made into the, well, they must have made it, but the amount must have been too little to have the toxic effect.

Speaker 2: Too little. And again, it's designed for mosquitoes, which are quite a bit smaller than leaf-cutting bees. And so it really surprised us though, because I thought, well, something about a housefly size, we'd probably see some death of those adult bees that were actively foraging or actively, well, not actively foraging at the time of spray, but they're actively provisioning and they rest in the nest shelters at night with their heads and bodies at the end of those nest tubes so they could easily be exposed. But yet not. So that's really interesting.

And it probably does relate to their bigger and the rate is so low. And it's not like the Zerosol cloud stays in the area forever. It dissipates very quickly. And it really is designed to knock down those adult female mosquitoes that are flying. So that surprised me.

I thought we'd see something. And also then we followed, hey, wait, okay, so the adults maybe aren't affected, those adult females, but what about their young? And so we looked at the larvae, even though, yeah, these leaf cells are pretty secure and everything. What about the eggs? What about the larvae?

And so we looked at that and didn't see any increase in the death rate of the large, the eggs, the larvae, or the adults. And this was kind of a field treatment that we did experiment that we did. But we didn't stop there. We also applied alfalfa in the evening at the time of bloom. And then at maximum labeled rates, so the high rates again, and then the next morning went out and collected alfalfa from where it would be the most exposed, the top part of the plant, brought that back and put leaf-cutting bee adults on that alfalfa.

Speaker 1: Oh, to simulate it, what would happen if they contacted the next day?

Speaker 2: Right. So they're, and so for 48 hours, they're crawling all over the alfalfa that's been treated. And we didn't have any increase in death. That surprised me a little bit too. Any increase in death from that exposure. And again, that's kind of an extreme case. It's applied the night before, goes out the next day, cuts it and puts it in containers, and then puts the bees in. And that's kind of a standard, it's kind of an EPA-approved approach for assessing risk to honey bees too. And so we did that and we didn't see anything or any increase in death rate.

So that was good as well. And then we also did some lab experiments where we looked at inherent sensitivity. We compared honey bees to alfalfa leafcutting bees and looked at the kind of toxicity and that kind of thing. So even with all of that, we didn't see really a much increase in risk at all. And we know based on what we overestimate or overdo the exposure, so to speak, that the risk is low actually. And we can manage pretty easily that risk by just doing something as simple as, you know, control districts or their alfalfa leaf cutting bee nest shelters out there, they can just turn off the applicator, turn off the sprayer as they're driving by the alfalfa seed production field and the alfalfa leafcutting bee production area. But we didn't do that.

As I said, we deliberately sprayed them and didn't see anything. So we know we're in pretty good shape here. We can manage risks to these pollinators pretty easily and probably extend that to, I would think that this kind of risk is similar for the wild solitary bees that are out there as well, the mason bees and the alkali bees that nest in the ground and bees like that. So we learned quite a bit and we're able to directly answer both mosquito control district questions as well as pollinator conservation people and their questions about this as well.

Speaker 1: Now, I guess the one thing that you didn't talk about, but doesn't make much sense from a mosquito control perspective is treating in the daytime. I imagine your mosquitoes aren't out at that time, so there's no benefit, a vector control district wouldn't apply these treatments during the day.

Speaker 2: No, I mean, there are day-biting mosquitoes, but they're typically not managed by treating during the day like this. There's a lot that feed only at night and they're in high concentrations and they're, and again, we're not talking about just treating for treating sake. It's when their numbers reach certain thresholds, but for the day-biting mosquitoes and a lot of mosquitoes that are, you might hear the word, Edie's, and like Edie's a gypti, the yellow fever mosquito, the Asian tiger mosquito, they feed during the day as well as at night, but they're not managed typically, adult management isn't as critical, it's more larval management or immature, the feed at the day and night, it doesn't lend itself. Also, if you were to treat during the day with these products, the mosquitoes aren't there, but they would break down very rapidly in the environment because of sunlight and they would dilute very, very quickly. They do anyway, but at night, there's not so much a risk of that light degradation from sunlight, things like that.

Speaker 1: Okay, fantastic. The one thing I did want to pick up on was one of the comments you made was around other bee species and the way in which toxicity for one species may represent, it could be generalized to broader species. Can you tell us a little bit about the work that you've done trying to look at the differential toxicity between bee species?

Speaker 2: Yeah, and it's important because we know so much about pesticides and honey bees and we use honey bees as surrogates, well, as replacements for other bees. And of course, as I think almost all of your listeners know, honey bees are very, very different, both in size and life cycle, life history, and behavior from these other bees. And just looking at alfalfa leaf-cutting bees and honey bees, as I mentioned, alfalfa leaf-cutting bees are about one-third the size of a honey bee. So you'd think, oh, well, that means they might be much more sensitive to an insecticide because they're smaller. That makes sense, right? Makes total sense. But guess what? Science doesn't always, isn't always about common sense.

Really? What we found is that honey bees are, for many of these materials, more sensitive. And so therefore, I think for the most part, they can be used as a surrogate for things, for other bees. You know, not everything, of course, but because we're talking about how many bees are there in the world, 20,000 plus species.

Right. And so you can't really generalize with bees as you and your listeners well know. But I think because they are larger but more sensitive, they can, for some other bees, they can be used as surrogates, a conservative, what we call a conservative surrogate. In other words, if you're protecting honey bees, you're probably also protecting these other bees because provided that, again, in the evening, these other bees aren't actively foraging and out in the environment. They're in their shelters or nests or burrows and that kind of thing. But the question is, why are honey bees more sensitive when they're three times bigger than say, alfalfa leaf-cutting bees?

And it's really interesting. Nobody's quite sure, but it's thought that because honey bees are truly social, each honey bee worker doesn't have to invest so much intolerance and resistance to the environment and in this case, tolerance and resistance to, say, pesticides or insecticides. And because there's so many of them, the workers are just the social nature, the true social nature of bees, of honey bees is such that they can, it's brutal to say, but they can afford losses of individuals. Whereas the solitary wild bees or solitary bees are non-social, the individuals have to be more resilient to the environment.

Speaker 1: You know, it just kind of explodes your idea of what there may be very life history-specific patterns to toxicity and different bee species. But it can also raise the problem. It would be really great if we happened upon the most sensitive species and then that could be a really good surrogate model.

Speaker 2: Right. Right. And also to remember, I always joke that honey bees are wimps compared to some other bees, but remember that we have deliberately bred honey bees to do our bidding to produce products we like, to pollinate crops we want. And so, because of that truly social nature, again, we don't have to have each individual worker be resilient to the resilient to environment that these solitary bees need to be.

And so, I think that's what's going on. And there's a lot of debate about mechanisms and we won't get into the biochemistry of insect toxicology and also why honey bees might be more sensitive. But we don't know everything yet, but it's really a fascinating area. And we're learning, we're learning a lot and trying to think how much honey bees, because a lot of the attention has been, well, you can't just look at honey bee data. You need to look at data and information from these other bees.

But yet, at the same time, when we can use honey bees as a conservative surrogate, we know we're protecting these other bees. And that's really cool. That is really a great thing.

Speaker 1: Well, I'm really glad that you didn't just take common sense and you tested it. That's awesome. That's science.

Speaker 2: Yeah, as I always tell my students in others, science often has little to do with common sense. And the best thing about science is, is not, well, yeah, the results are what we expected. But when you go, hmm, that's interesting. That's where the real advances in science are made, right? And so, it's important not to just guess at these things, but actually research so that you can have those moments of, hmm, I didn't expect that. And so, that's where we really make progress in science.

Speaker 1: I just wanted to come back to this question of options. So, it sounds like vector control, you were talking about, there was that fascinating part where you're talking about different types of mosquitoes, not one species. Vector control districts have a large mandate. There's a complicated, a complicated set of decisions that they have to make.

Can you tell us a little bit about, you know, kind of reflecting on your work, what would be some best management practices? What are the various options that they have for being able to deal with mosquitoes in these high-risk situations?

Speaker 2: Yeah. And it's, we've been talking almost exclusively about these managing adult mosquitoes with these adult asides or these insecticides that are used for adults. But obviously, there are all kinds of other things that are used. And I think it's important to stress that a lot of mosquito control districts around the United States use integrated pest management principles.

And so, and so, what does that even mean? It involves the identification of mosquito species and the surveillance of their populations. There's a lot of knowledge that has to be used in understanding just that, what species are out there, and then how we sample or surveil the populations. And so, when these populations of larvae, pupae, adults, or say pathogen pathogen-infected adults that have West Nile virus, the mosquito populations with West Nile is just one example. When they reach these threshold levels, which we talked about before, then actions might be taken to lower those populations below those thresholds. We're really never talking practically about the eradication of mosquitoes. Yes, when we have some invasive exotic mosquitoes, we might be thinking, can we, go from the fewer findings to zero, but almost always we're talking about managing populations to go eradication. And so, the tactics that are used within this integrated pest management framework are really about habitat reduction, or some people think of that as breeding sites. So, you manage water resources to limit the production because the imagers live in water. And they filter feed on decaying plant vegetation and things like that, that they don't blood feed, they don't feed on blood, the images, but that's where the adults come from ultimately. And so, some of it is involved with limiting water breeding areas or sources, so the habitat reduction.

That's really important. Other tools are, you could have mosquito fish that are released. So, these are like these little minnows. There are a couple of different species.

Really? But they release these mosquito fish in areas where the mosquito fish themselves won't hopefully pose a problem because they don't, mosquito fish eat more than just mosquito larvae. But the mosquito fish, when they're released, especially in the kind of contained areas, can clean up problematic numbers of mosquito larvae, these images. And then there are products as we talked about with the adults, there are products that just target immature mosquitoes, such as spores that are produced from a certain bacteria, that BTI, you might hear BTI, which is short for bacillus thuringiensis isrelensis.

And that's why we say BTI because nobody wants to say the full term. Essentially, this is a toxin that's produced by this bacterium that only is specific to mosquitoes and a few other flies. And so, it's not toxic to mammals and fish and people and so on and so forth. And so, you put that in the water and it, as the mosquito larvae or imagers are feeding, they pick that these spores up and this toxin up and this larval management tool knocks down the populations. And that's often used in these mosquito control districts, as we ratchet through, as we go through the different things that can be used. And then, of course, we talked about the products that are used that target adult mosquitoes, these mosquito management products. And so, it's a whole toolbox that's used and it's used with scientific knowledge. And it's used by public health professionals too.

And so, it varies from, you know, you have small districts that do certain things, mosquito control districts that do have the ability because of resources to be more sophisticated. But the goal here is that we manage populations using the best science to have a minimal impact on the environment. And that's something we shouldn't lose sight of. That's the ultimate goal. That's what's done oftentimes. And it's what, you know, it's just good management strategy and practice.

Speaker 1: Well, in addition to using integrated pest management and being very specific and deliberate in the treatment, are there any other best management practices specifically around doing vector control around managed pollinators?

Speaker 2: Yeah. And that's what several of us are researching. And of course, what we're finding, and you've had other guests, I think, on the show that have dealt with this, that do research in this area. And what we're finding is, you know, these existing labels are, which is kind of the risk management guide, the labels for these different products, they're really quite good. And they do, if you apply according to those labels, if you treat mosquito populations according to these labels, you can manage the risk very effectively. And the risk can be quite low, both for honey bees and some other bees and so on.

So, you know, I always, I want to find the, oh, we didn't think about that. But so far, we're finding out that, hey, EPA does know what it's doing. The state environmental agencies and departments of AG do know what they're doing. And they were not unduly putting entire species or populations at an unacceptable risk because of what we know and the science that's allowed us to develop these managed outages.

Speaker 1: That's great because I know here in Oregon, we have a big focus on, you know, educating applicators on being able to understand the label language, which sometimes can be a little complicated, and just, it sort of reinforces that that's a really key part of a pollinators protection strategy when it comes to pesticide applicators.

Speaker 2: Yeah, absolutely. Education is critical and training of applicators, is absolutely critical here so that really bad mistakes aren't made, whether it's with a higher rate or whether, which is hard to do with ultra-low volume application equipment. But things can be done really poorly, such as applying these materials for adult mosquitoes, like during the day or mid-morning or even morning when all the forages are coming out. Again, these are, these are highly toxic materials, 2Bs, but they can be applied in such a way that greatly limits the exposure and therefore limits the risk. Fantastic.

Speaker 1: Well, let's take another break and I've got a couple of questions I ask all my guests. I am really curious what your answers are going to be. All right, so we're back. I ask all my guests the same questions. The first one is a book recommendation. Is there a book that you really want people to check out?

Speaker 2: There is. And there's a book I really love that was published last year in 2017. It's called The Secret Life of Flies by Dr. Erica McAllister, who's at the British Museum of Natural History, and she studies flies for a living.

And I just love the book because she, in a very readable, easy-to-read book that doesn't take too long to read it. She tells stories about the diversity of flies and also all the really big things that these flies do. And the reason I'm bringing that up here is because flies in a lot of flies, especially flies in certain families, can be our very important pollinators. And a lot of those flies look and mimic bees. And so some people might see them and think, oh, that's a bee, but it's actually a fly. Dr. McAllister goes through some of the stories about the importance of flies as pollinators in this book. So The Secret Life of Flies.

Speaker 1: That's fantastic. I have to shamefully admit we have not done a single episode on pollinating flies. I have to remedy this. I'll have to give her a call.

Speaker 2: Yeah, her or there's others too that work with these various flies. And they can be like I said, very important pollinators. They're kind of forgotten about because everyone's focused on bees, bees, bees as the main pollinators. And for sure they are, but in some environments, flies can be more important than bees because they're just so much more numerous. And they're in areas where there aren't a lot of bees.

Speaker 1: They seem to fly at lower temperatures and there are some plants. I know we have in Oregon, this Oregon bee atlas, we have volunteers that are going out or collecting and curating specimens from across the state. And I know we were just in Bend last week and a number of volunteers were like, well, we want to do the flies. Why won't you let us do the flies? And I was like, I don't know anything about them.

Speaker 2: Yeah, they're not easy to study. But in some areas like high mountain areas and alpine, subalpine, and especially alpine areas, flies can be where it's at when it comes to pollinating wildflowers, mountain, high mountain wildflowers.

Speaker 1: That's a fantastic recommendation. It's never been recommended before. You're breaking new ground.

Speaker 2: Oh, good. Glad to hear that.

Speaker 1: Okay. The next question I have is, do you have a go-to tool? Is there a tool that you really love for doing the kind of work you do?

Speaker 2: Yeah, when we work with this, this isn't so much a tool, but it's a parallel option. And that when working with leaf-cutting bees, you don't have to necessarily dress like you would for working with honeybees and hives. Leaf-cutting bees do sting. They don't leave the stinger behind. So it's not as painful as a honeybee sting. But when you're in front of those nest shelters with thousands and thousands and thousands of female bees doing their thing, they tend to, just because of the sheer numbers, want to fly everywhere. And so you have to wear sleeve shirts that are kind of maybe even rubber bands around the ends of those, the end of the shirts and at the end of the arm and things like that.

You don't have to wear a mask, but you do have to make sure to dress so that they're not flying up into your body from shorts you're wearing or short-sleeved shirts and that kind of thing. Otherwise, they're fairly easy to work with. And all the little things we talked about, such as the peg boards and the bee boards and all those things, those are all tools that we use to study these bees.

Speaker 1: So is your answer an elastic band?

Speaker 2: Yeah, elastic band, because the most uncomfortable thing is when they fly into your shirt and then down into your chest and other places that we won't mention. It can be just off-putting. Let's put it that way. It might not even sting you, but it's still off-putting and can distract you from the high-level research that we do.

Speaker 1: Wow. You are a real renegade in your answers. I'm really curious about question number three, which is, do you have a favorite pollinator?

Speaker 2: I do, and it's related to the secret life of flies. And that is, I love flower flies. The family's called surfing. And one of the common names is flower flies. And also you might hear them referred to as hoverflies. And they're the ones that often are mistaken for bees because it's unbelievable how some of them can mimic bees, both bees and wasps. And so you'll have these flower flies that look remarkably similar to both like furry bees, hairy bees, like bumblebees, but then also that looks like a lot of wasps as well. Some look like bumblebees, some look like honeybees, and some are different wasps.

And they, again, can be quite important as pollinators for not just wildflowers, but also for crops in various areas and temperate and tropical areas. And so they're my favorite. I love it, I'm an insect photographer too, and I love taking pictures. I've got a soft spot for flies in general, but I love taking pictures of these flower flies. And again, yeah, I'm looking forward to listening to an episode that you do where you focus on flies as pollinators because we don't want to leave them out.

Speaker 1: The pressure is on. I'm glad you made the recommendation and I'm on the hunt. If we have any fly pollinator biologists out there, you better write me. Well, this was really great. We covered a lot of ground, not only leaf cutter production methods, but we also went into another episode building on the episode with Kirsten Healy, this important issue of pollinators and vector control. This was a great episode. Thank you so much for being so generous with your time.

Speaker 2: Well, thank you. And thank you for having me. It was great.

Speaker 1: Thanks so much for listening. Show notes with information discussed in each episode can be found at pollinationpodcast.oregonstate.edu. We'd also love to hear from you, and there are several ways to connect. For one, you can visit our website to post an episode-specific comment, suggest a future guest or topic, or ask a question that could be featured in a future episode. You can also email us at [email protected]. Finally, you can tweet questions or comments or join our Facebook or Instagram communities. Just look us up at OSU Pollinator Health. If you like the show, consider letting iTunes know by leaving us a review or rating.

It makes us more visible, which helps others discover pollination. See you next week.

Alfalfa leafcutting bees (Megachilie rotandata) don’t make the headlines like honey bees do, but they are pretty important to agricultural production. These bees pollinate alfalfa plants to make the seed that gets planted out across hay fields across the US and beyond. This week we learn about the peculiar management system associated with leafcutting bees. Our guide is Dr. Bob Peterson, who is Professor of Entomology at Montana State University, where he leads the research, teaching, and outreach program in Agricultural and Biological Risk Assessment. Dr. Peterson also shares insights from his work around alfalfa leafcutting bee management and vector control.

Dr. Peterson has authored or co-authored 110 peer-reviewed journal articles, 14 book chapters, and one book. He teaches undergraduate and graduate courses, including environmental risk assessment, insect ecology, and various special-topics graduate courses. In 2019, he will become president of the Entomological Society of America, the largest organization in the world serving the professional and scientific needs of entomologists and people in related disciplines. Founded in 1889, ESA today has more than 7,000 members affiliated with educational institutions, health agencies, private industry, and government.

Listen in to today’s episode to learn about the uniqueness of leafcutting bees, how they’re managed, and how to keep your bees safe in using pesticides.

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“The goal here is that we manage populations using the best science to have the minimal impact on the environment. That’s the ultimate goal.” – Dr. Bob Peterson

Show Notes:

  • How alfalfa leafcutting bees are managed
  • The life history of the alfalfa leafcutting bee
  • Why honey bees are not good pollinators for the alfalfa crop
  • The technology used to manage alfalfa leafcutting bees
  • What conflicts arise between mosquito control and managing leafcutting bees
  • Why understanding the difference between toxicity and risk is so crucial in using pesticides
  • What techniques leafcutting bee operators can use to minimize collateral damage of pesticides
  • Why honeybees are more sensitive to pesticides, despite being larger than leafcutting bees
  • The alternatives to pesticide in combating mosquitoes
  • Bob’s advice for those managing leafcutting bees on minimizing their exposure to pesticides

“When you look at an alfalfa field, if it has what looks like little metal or wooden sheds in the field, that’s where hundreds and hundreds of thousands of leafcutting bees are doing their jobs.” – Dr. Bob Peterson

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