Plastic Bands, Pesticides, and Deadly Drift: A Study on Mosquito Spray

Who doesn’t know the high-pitched whine of a nearby mosquito? We know they can be a nuisance, and in many regions, a health risk because of their ability to spread diseases. Some communities do public control campaigns, and increasingly, companies are offering home spraying of yards. But, the insecticides used in these sprays are broadly toxic to insects, and the risk they pose to pollinators isn't fully understood. In the summer of 2023, Xerces did a study looking at how these insecticides spread across the landscape. 

Joining us to talk about the study is Aaron Anderson, who has been a member of Xerces’ pesticide reduction team for a couple of years. Aaron’s work focuses on reducing pesticide use in residential landscapes, including promoting alternative pest-control measures and pollinator-friendly gardening practices. Prior to joining Xerces, he researched pollinator conservation in urban landscapes, restored habitat for several endangered butterfly species, and worked in insect biocontrol. If that wasn’t cool enough, Aaron has been on Bug Banter before, also talking about mosquitoes.

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 Photo: Woodland Mosquito-Katja Schulz-Flickr CC

Thank you for listening! For more information go to xerces.org/bugbanter.

Transcript

Matthew: Welcome to Bug Banter with the Xerces Society where we explore the world of invertebrates and discover how to help these extraordinary animals. If you want to support our work go to xerces.org/donate.

Matthew: Hi, I'm Matthew Shepherd in Portland, Oregon.

Rachel: And I'm Rachel Dunham in Missoula, Montana.

Matthew: Who doesn’t know the high-pitched whine of a nearby mosquito? We know they can be a nuisance, and in many regions, a health risk because of their ability to spread diseases. Some communities do public control campaigns, and increasingly, companies are offering home spraying of yards. But the insecticides used in these sprays are broadly toxic to insects, and the risk they pose to pollinators isn't fully understood. In the summer of 2023, Xerces did a study looking at how these insecticides spread across the landscape.

Matthew: Joining us to talk about the study is Aaron Anderson, who has been a member of Xerces’s pesticide reduction team for a couple of years. Aaron’s work focuses on reducing pesticide use in residential landscapes, including promoting alternative pest-control measures and pollinator-friendly gardening practices. Prior to joining Xerces, Aaron researched pollinator conservation in urban landscapes, restored habitat for several endangered butterfly species, and worked in insect biocontrol. And if that wasn’t cool enough, Aaron has been on Bug Banter before, also talking about mosquitoes.

Matthew: Welcome back, Aaron!

Aaron: Well, thank you, Matthew, and thank you, Rachel, for having me. You all do such a great job with this podcast. It's fun to be on and chat about science and invertebrate conservation with you both. And yeah, I'm excited to talk about the study that we performed. Yeah, looking at these pesticide residues from residential mosquito sprays and chatting a little bit about what we found, and kind of the concerning levels resulting from these sprays.

Rachel: Yeah, we're anxious—we've heard a lot about the study, but not the results. So before we dive in, however, can you briefly describe what an insecticide is, and how does that relate to pesticides? You hear people using those terms interchangeably.

Aaron: Yeah, you do hear people use those terms interchangeably. So that's a really good question. So a pesticide is a product, generally, you know, a chemical designed to kill a living organism that we don't want—the pest. So this is kind of that broad umbrella term. And then under pesticides, we have herbicides which kill plants, fungicides which kill fungi, and then insecticides which kill insects. And there's a lot more other categories, but it can also be a little bit gray too, like some insecticides are also miticides and kill mites. But in general, an insecticide is a pesticide that targets insect pests. And that's why they're particularly risky to insects—to insect pollinators and other beneficial invertebrates like fireflies, lady beetles in your garden, itty bitty tiny parasitoid wasps, predatory ground beetles, all sorts of these, you know, insects that we love and we want to protect. Because insecticides are designed to kill insects, many of them are very broad spectrum, too, meaning they can't discern between a pest like an aphid and then a little native leafcutter bee in your garden. So yeah, that's why insecticides are particularly risky to these beneficial organisms, because they're unfortunately designed to kill them.

Matthew: Yeah, I know we're going to be talking about your mosquito spraying study today, and I was wondering what the catalyst was for doing that in the first place? And I don't know if that also reflects on what you were just saying about insecticides being so broad spectrum.

Aaron: Yeah, you know, it does. And that's a great question. So in my position here at Xerces, I work a lot in residential landscapes and towns and cities to reduce pesticide use, and to encourage pollinator friendly gardening and landscape management practices. And so one of the questions that I get—and I know we get on the pesticide reduction team, in general—is somebody who's concerned because they're creating pollinator habitat in their yard, but their neighbor might spray pesticides. And they're wondering whether they should not be creating habitat next to that yard where their neighbor is spraying pesticides. And frequently, it is, you know, spraying for mosquitoes—that's kind of the question that these people have about—. And, you know, people were wondering if, yeah, they shouldn't be creating habitat next to this area where pesticides are being sprayed. They wonder whether they're essentially creating an ecological trap—is what we call it. Essentially luring pollinators into what appears to be really good high-quality habitat, when it's actually going to be really poor-quality, and in this case, potentially poison them.

Aaron: So we didn't really have a great answer to that question. There hasn't been a ton of research done about, you know, if somebody's spraying in a yard, how much of a risk is it next door? So we decided to try to get a sample of backyards that were being sprayed for mosquitoes, or I should say, neighboring yards being sprayed for mosquitoes, and sampling the adjacent yards to get a sense of how much insecticide residue is actually being deposited. And then also what insecticides were present from these sprays. So that was kind of the catalyst, just getting these questions from Xerces members, to be honest.

Matthew: Yeah, no, I can totally understand that. Because if you've put much love, and much time and energy into creating a beautiful pollinator garden, the idea that it's being damaged and harmed by your neighbors must be gutting.

Aaron: Yeah, exactly.

Matthew: Yeah, so I mean, what was the purpose of the study?

Aaron: Yeah, okay, great question. So I kind of touched on that a little bit on the last, on the last question, but to kind of set the stage, mosquito spraying is, of course, a source of pesticides and insecticides in urban landscapes. And as we know, pesticides are a large contributor to pollinator declines. So we want to do whatever we can to prevent pollinators, and those other beneficial insects that we care about, from getting exposed to those pesticides. And there's two main types of mosquito sprays that happen in our towns and cities.

Aaron: The first are barrier sprays. And this is what happens when—generally when—you hire one of those spray surfaces that comes to your yard. What they're doing is they're spraying a pesticide, an insecticide—here I am using that term interchangeably. They spray an insecticide—I should be clear—on the vegetation around your yard, to kind of give it—[to] coat the vegetation, so that mosquitoes that land on that vegetation to roost—because mosquitoes aren't flying all the time, they're active at certain times of day, and they'll kind of take shelter during other times during the day. So when they come in contact with that barrier spray, they'll be exposed to the insecticide and die. The spray also will get some of the adult ones that are out flying when that treatment's happening.

Aaron: And then there's the vector control district sprays where, you know—whether it's the county or a hired contractor for the municipality—they'll go out and spray the entire community. And this is generally with a truck that kind of fogs the pesticide, kind of turns it into an aerosol. And it's a really small droplet size, so it can kind of float on the breeze and settle out and kill adult mosquitoes that are flying. And sometimes this is also an aerial spread—they'll do it via plane. But those are kind of the two main mosquito sprays.

Aaron: And the chemicals used to spray for mosquitoes, both at home and also with these more community wide sprays, tend to be very broad spectrum, meaning they'll kill mosquitoes, but also impact all sorts of other insects, as well. And these are largely pyrethroids, you know, this really toxic group of insecticides. But sometimes for vector control district sprays, they also use organophosphates—also very toxic. Yeah, and then also sometimes they'll include an insect growth regulator, which will halt the development of juvenile insects, as well, to kind of, yeah, just add as many pesticides into this mixture as possible to kill mosquitoes.

Aaron: So, with that in mind, we had some main questions. So first, we were wondering how much residue is deposited from these private backyard mosquito sprays, again, also known as barrier sprays. And this wasn't actually initially one of our research questions, but as we recruited volunteers to participate in the study, we actually had four volunteers who actively have their yard sprayed for mosquitoes. So we weren't anticipating this, but we were able to get some numbers for yards that were, you know, actually being sprayed, which was honestly pretty interesting and exciting.

Aaron: And second—I kind of mentioned this as the catalyst for our study—but how much pesticide residue drifts from a neighbor's application into a nearby yard, if that neighbor hires one of those spray services? And then our third question was: how much residue results from vector control district sprays? And then finally—kind of the root of all this is—we wanted to assess what risk that detected amounts of residue that we were finding posed to pollinators. So that's kind of—I hope that makes sense as kind of a breakdown of what we were interested in looking at.

Matthew: Yeah, no, definitely. It seems like a pretty nasty soup of stuff that these companies and the vector control districts are throwing out there.

Aaron: Yeah, it definitely can be. You know, I can talk about this a little bit when I talk about the results, but not only are they sometimes doing a mixture of multiple pyrethroids, maybe an insect growth regulator, but then also they'll add a synergist. The most common one used—and the one that we detected is—piperonyl butoxide, or otherwise known as PBO. But it actually increases the toxicity of these insecticides in combination. So they're also adding these other chemicals that are just, yeah, kind of amplifying that toxicity—if these pyrethroids weren't toxic enough to begin with.

Matthew: They must be toxic, because that's why they're using them. You've already mentioned gardeners, that you were recruiting volunteers, and so on—where did you do this study, and was there any particular reason why you chose that area, or those geographic locations for it?

Aaron: Yeah, great question. So we actually recruited volunteers in three different states. The first was Decatur, Georgia, which is one of Xerces’s Bee City USA affiliates. And they do a lot of really great education and outreach on the risks of mosquito sprays. And through the Bee City pipeline, we were able to reach our contacts on the ground there, and they were able to do outreach themselves, and recruit volunteers for us, which was amazing—can't thank them enough. And then we had a partner, Good Neighbor Iowa, in Iowa, and they also had this kind of network of volunteers that we were able to kind of recruit volunteers through. And then finally, we recruited volunteers in Massachusetts because Rosemary Malfi, our policy director here at Xerces, previously worked doing pollinator conservation in that area. So she had a lot of contacts that she was able to reach out to, and also was really great and did on-the-ground collection work of the bands, and shipping them. So I can't think Rosemary enough for her help with this, as well. But yeah, that's kind of how we picked those three areas. We picked states where there's active spraying going on, but then we also had kind of this on-the-ground network we were able to kind of leverage.

Matthew: Yeah, that's great. It must be hard to try and implement a project—a research project like this—without local contacts. So shout out to everybody who helped and collaborated on, it for sure.

Aaron: Yeah, I can't thank all the volunteers enough. And then also the kind of point people on the ground who did the collection of the bands. And I guess I'll talk about the bands more in a second here, but collecting our sampling materials and sending them off to the lab. Yeah, I couldn't have done it without the help of everybody.

Matthew: Yeah, I was going to ask—this is probably a really short answer now—but from what we know about mosquito spraying, do you think that's a cause for concern for its impact on pollinators? And it's almost like, is that a yes or no answer really, isn't it? Haha.

Aaron: The answer is yes. Haha. Thank you for asking, Matthew.

Matthew: Great, let’s move on. Haha.

Aaron: Yeah, as I mentioned, we know that the insecticides that are used are broadly toxic, and there have been a few other studies that suggest with these barrier sprays, they're toxic for two to three weeks afterwards and still impacting mosquitoes, as well, as potentially other beneficial insects. And we also know for municipal sprays, or vector control district sprays, that there have been bee die-offs, butterfly die-offs reported as a result of these sprays. So yes, there is plenty of reason to suspect that there's cause for concern on the impact to pollinators from these sprays.

Rachel: So you've talked a little bit already about the locations and sort of who is involved, but let's take maybe a little bit of a deeper dive into the methods—who are these folks that volunteered, how did you recruit them? How did you do this study? I'm interested in hearing more about these bands.

Aaron: Yeah, so okay, initially we wanted to find people who had neighbors who sprayed for mosquitoes because, as I mentioned, that question of drift is a really, you know, was a big reason for doing the study to begin with. So we were trying to recruit people who had neighbors who sprayed for mosquitoes. So through our contacts on the ground in these three different states, we had them do outreach through their networks, essentially, through Good Neighbor Iowa's volunteer network, through Bee City USA, and then also, as I mentioned, Rosemary had these contacts through the Massachusetts Pollinator Network. So we recruited people who would hopefully be interested in participating in our study and would be curious to know whether their neighbors had a drift that was impacting their yards, and potentially their pollinator gardens. And then, as I mentioned—what was, you know, I think, I hate to say it, a pleasant surprise, because obviously mosquito spray isn't something I want to happen—but the fact that we had four people who did actually have their yard sprayed for mosquitoes, I thought was a really great thing to include in the study. So yeah, we kind of just did outreach through these different groups.

Aaron: And then, yeah, the next question was: how are we going to kind of sample these residues? And I should also mention that we also wanted people who we're relatively certain of the spray schedule because there was—you know, we had a pretty big response, which was great—but there was a lot of people who were like, “Yeah, I think my neighbor sprays but I don't really know when.” Or, “I saw them spray once,” which is, you know, I'm so happy they responded to us—I appreciate it—but we really needed somebody to be pretty sure. Like, “Oh, yeah, it happens, you know, once a week or every three weeks on this day,” and they could put sampling materials out.

Aaron: So then, yeah, getting to that next question of: how do we actually capture this drift? With some of our previous Xerces sampling projects, we've sampled vegetation. So we've taken samples of leaves and had those analyzed for pesticide residue. So initially we were kind of thinking we would do something like that, but the challenging thing with plants in a yard is there's no way to control how far it is from a property line or from a road. And then, plants can have such different characteristics. So you might have a plant with a waxy cuticle, you know, waxy leaf like a magnolia. Or maybe you have something like a lamb's ear that's covered in those really fuzzy trichomes. And you can imagine that pesticide drift would potentially being deposited on those differently. And it was kind of this big can of worms.

Aaron: So what we decided to use were these silicone bands. Those bands, you know, like a Livestrong bracelet from back a few decades ago at this point. Haha. Or, you get them, you know, with all sorts of different phrases or causes, you know, kind of printed on them. So they're actually really great because they capture all sorts of chemicals in the silicone. And they first started to be used in kind of human and environmental toxicology studies. I think one study was like having firefighters wear them for a week to see what they're exposed to. But recently, they've been being used more and more in pesticide monitoring and ecological studies, being put out in the field for a month to see what pesticides are captured by these bands. And what's really nice is they're a consistent material, a consistent size, a consistent surface, unlike plants. And then also we can have the volunteers place them consistently in the same places in a yard.

Aaron: So for the actual deploying of the bands, we mailed them all the materials, we mailed them bands, we mailed them these hooked wires. Think of those little pin flags used to mark like an irrigation pipe, with the flag stripped off. I kind of bent them into hooks so people could place them in the ground, put the band on it, and just have them set up in the yard. And the volunteers replaced them before a known spray event would happen, and that they'd collect them the day after, after the spray had dried. And then they would wrap the bands in foil, put them in a Ziploc, store them in the freezer until they were collected and shipped off to a lab overnight, and analyzed for, I believe, over 300 different pesticides. So that was kind of in a quick nutshell how the study went: we mailed people silicone bands, they placed three of them in the yard, and then we collected them and analyzed them for residues.

Rachel: To give us a sense of numbers, how many people—like how many yards participated, how many bands did each yard use?

Aaron: That's a very important question—it would be good to know. We ended up sampling 26 yards. And 13 of those were neighbor drift sites, and then again, those four yards that had hired a service actively spraying their yard. Seven of them were sprayed by vector control district sprays, and then two sites were control sites that didn't have any known spray events during the time that the bands were up. Yeah, and then I believe we had 78 bands total. I think we lost one. I think one got run over by a lawnmower.

Rachel: Oh, no. Haha.

Aaron: Haha. Yeah, a little bit of attrition, but so it goes.

Rachel: Not too bad. And did anything surprise you or pop up that you didn't expect?

Aaron: Yeah, so I think one of the biggest surprises in running the experiment, honestly, was the fact that we did find, or we did recruit four sites who actively sprayed for mosquitoes. You know, from this kind of pool of people who are pretty ecologically minded, and I think just goes to say—and I don't say that in a judging way, at all—I think it just shows how pervasive, you know, are—the messaging from often these mosquito spray companies are about it being kind of needed, and safe, and things like that. And then also just how pesticide use is really normalized societally. Which I think is why the outreach we do at Xerces is really important because, you know, I think often people think about pollinator conservation, they think about planting flowers, and nesting habitat, which is totally, you know, probably the most important part, obviously. But then pesticide reduction, and protecting these spaces from pesticides is also a really important part, but sometimes I think people don't realize. So I think that that was, that was a surprise for me. But yeah, I'm glad that we did recruit some people so we could kind of get some of these differences from these different types of sites.

Rachel: Thanks for answering that question.

Matthew: All right, big moment. Feel like a drum roll needed here—results. We've been anxiously waiting—what did you find?

Aaron: Yeah, okay, so we found a good amount of pesticide contamination, insecticide contamination. Haha.

Matthew: Wow. Haha.

Aaron: Wow. Haha.

Aaron: So we found—so for quick overviews here, we found the pyrethroid Bifenthrin in 53 out of 70 out of the non-control samples, which I was honestly quite surprised by—it really shows how pervasive this insecticide was across these sites. And sometimes it was obviously like the main thing at really high levels, but other times it was really small amounts, kind of trace amounts, just kind of in the background. So that was a big result. We detected five pyrethroids overall. Again, sorry if just reading results here is boring, but just for reference, we found 1,500 nanograms per band in sprayed yards, and 28.6 in yards with neighbor drift, and then 7.3 in vector control district-sprayed yards. So those numbers don't really mean anything, necessarily, when you just hear them, but it kind of shows there was a ton that we found in yards being actively sprayed, as one would expect. A few orders of magnitude less in drifting into neighborhood yards, and then relatively low amounts in vector control district-sprayed yards.

Aaron: Then that kind of does beg the question, right? It's like, what does this mean? What does 1,500 nanograms mean? So we did some math to try to go from how much pesticide residue was sprayed on these bands, to how much would be sprayed on a bee, and what would that mean for that bee? So we used honey bees as our model because, unfortunately, pesticide toxicity isn't known for most of our native bee species. So we had to use honey bees. But what we found was that yards sprayed by these barrier spray services had on average over six and a half times the amount of pyrethroid that are toxic to honey bees, or I should say that are lethal to honey bees. And the yards with the highest values were over 34 and over 24 times that lethal dose for a honey bee. So just really high levels of pyrethroids.

Aaron: So then these yards with neighbor drift had much lower—on average 12% of a lethal dose for a honey bee. But in the highest level in neighbor drift yards, was actually two times that lethal dose. So that potential for acute risk is still there in these neighbor drift yards. And then as I was mentioning, these vector control district sprays were lower, with an average of—if I'm doing my math right—just about 3% of the honey bee LD50, with the highest that were recorded being about 13% of that LD50. And I think that was interesting, but I think also the way that these sprays are being done does kind of explain some of those differences. As I was mentioning, these barrier sprays are being done with larger droplet size with the explicit goal to coat things, versus these municipal sprays that have these really, really, really small kind of aerosolized droplet sizes, kind of drifting out across the broader landscape.

Aaron: So I think this is where I probably do want to put in a plug—just because values are low or lower than some other values doesn't mean that there's no risk. So, as I mentioned, these yards that had neighbor drift, there were still several yards that had over that lethal dose for a honey bee. That's a lot of pesticides. That is something to be concerned about. But even at these lower levels, there can be these—. You know, at levels that don't kill a honey bee, or a bee, or a butterfly, there can still be these harmful impacts. So it might not kill the individual, but these low levels of exposure might make them develop slower. It might make them forage for food less efficiently. It might make them not be able to navigate as well. All of these things, again, might not kill the individual, but over time can add up at the population level and impact populations.

Aaron: And I should also note, for these municipal sprays, we have documented events where municipals—or I should say vector control district sprays—have resulted in bee die-offs and butterfly kills. So we looked at this really small kind of picture—you know, we had a handful of sites, handful of vector control districts, and there might be different practices, different equipment calibration, different chemicals used. There might be all of these different variables that could go into whether or not one of these sprays is—you know, how toxic it is, essentially.

Aaron: And also, I should note, too, that all of these were just this one picture of one spray event. But we know these were happening—for these barrier sprays, it's generally every three weeks throughout the entire flight season of mosquitoes. So in some places it's February through November, or maybe March through October. And similar, with these vector control district sprays, they're happening—in some cases, depending on the district—they can be routine. So what the—kind of that over and over again exposure, that chronic exposure is, is something that we weren't able to assess in our study. So just wanted to kind of put that question of risk in a little bit more context.

Matthew: Sure. And I know you were saying that the data was based upon what we know about honey bees. And that’s a topic of a different podcast and episode, as it happens. From what you know, I mean, native bees are often much, much smaller. You know, much bigger surface area compared to body volume, etc. So do you have a sense of whether those—and obviously we don't have the data—but do you have a sense of whether these exposure levels are more—potentially more—impactful to native bees?

Aaron: Yeah, depending on the species, you know, there's research that suggests that—and again, this is also dependent on the insecticide, or the pesticide—but yeah, they certainly may be more toxic to our native pollinators than to honey bees. You know, like you were saying, Matthew, you have some native bees that are tiny, you know, the size of a grain of rice. You also have larger bees, as well. But there's also the physiology that's potentially different, as well, and the ability to detoxify some of these chemicals. And that was a huge challenge with this and trying to get a sense—. And this is one of the issues with trying to assess risk to our native pollinators from pesticides, in general, is that there just isn't very much data out there.

Aaron: So we were actually able to find these—kind of this toxicity data for one of the pyrethroids we detected and monarch butterflies. We were able to find it for a different chemical and then common buckeyes and painted ladies. So we were able to calculate the exposure from these individual pyrethroids—which again, were just one out of five that we detected, which kind of helped give us a glimpse—and we did find that some of these yards did have amounts that would have been toxic to monarch caterpillars. But yeah, unfortunately, there's just not a lot of data out there, which makes it a lot harder to kind of drill down on the impacts that these pesticides are having. But like you said, [we] do know that for a lot of these different species, they may be more sensitive than honey bees, but they're kind of our best measuring stick right now.

Matthew: Oh, yeah. No, I know we can only work within the data we have, because it’s science, right?

Aaron: Exactly.

Matthew: Yeah. And I mean, given that's the limitation, I mean, can these results be applied elsewhere? Do these results only really apply to the areas where the studies were done, or could they be generalized, do you think?

Aaron: That's a really good question. Yeah, so I certainly think they can be generalized, with kind of the caveat that this was in many ways, I would say, like a preliminary study. I would love for some other researchers to take kind of this idea and run with it and have a much larger sample size, across a broader geographic region, and potentially track this over time for like a full season, as I mentioned, to kind of get a sense of that chronic exposure, versus just these acute, one-time exposures. But these backyard sprays are, you know, not uncommon across much of the entire country. You can find these services in the Midwest, and the Northeast, and the Southeast. And there's no reason to think that the way that they're being applied in Iowa and Decatur are necessarily any different than they would be in New York or Nebraska. So I think we can—you know, you obviously want to be cautious not to overgeneralize—but I think we can say that the study is suggesting that there is a really high level of risk from having your yard sprayed by these services.

Aaron: And then I think it provides, you know, what we were looking for when we set out to do it—to begin, at least, to get an idea of what the risk is to these neighboring yards, so that we can finally tell people—. I think it's kind of hard to thread the needle on this, right? Because there was a lot of yards where the exposure wasn't super high. The drift might have been a little bit more minimal. But then we did have yards where it was over the honey bee lethal dose. So I think not dissuading people from planting pollinator habitat, even if their neighbors are potentially spraying for mosquitoes, but still saying that, “Hey, this is still a potential risk, and mitigation is important. So if you have the type of relationship where you can actually go and talk to your neighbor, and talk about your concerns, and see if they'd be willing to adjust their practices, that would be fantastic. If not, then maybe you do want to plant your pollinator habitat on the other side of your yard. Maybe you could plant some kind of mitigation strategies like non-flowering arborvitae, some sort of non-flowering shrub, that will serve as a drift barrier to kind of intercept some of that drift.” So I think still trying to do strategies like that to minimize the risk to the pollinators in your yard is still important.

Rachel: It just makes me think of like boundaries of yards, that like bees and other pollinators don't care. Like they can travel between yards. So, you know, maybe the impact is less in your yard, but that doesn't mean that they aren't traveling over—. But same with mosquitoes, you know. Mosquitoes are going into your neighbor's yard. So it makes me wonder how effective is spraying for mosquitoes in the first place, if your neighbor has a feeding ground for them—breeding ground? Seems like we should all work together, right, to find solutions that are good for everybody and for pollinators. It just makes me laugh a little because wildlife doesn't care about boundaries at all.

Aaron: Exactly, Rachel. No, that's such a good point. I think that, yeah, mosquitoes are mobile. They can fly across property lines super easily. So that's one of the reasons we do say that mosquito management is most effective at that kind of neighborhood or community level. And yeah, talking to your neighbors about removing standing water. As I mentioned, Decatur—you know, again, we sampled there—they’re a Xerces Bee City. They have a really amazing community outreach program where volunteers do talks, table at events and nurseries, put up signs about the risk of mosquito spraying and solutions. I encourage you to check out their website, Beecatur, for some inspiration on kind of some of that community-wide mosquito management.

Rachel: Yeah, definitely. I can put that in the show notes. And I can also include your previous podcast about mosquitoes, and mosquito spraying, and lots of great tips on how to reduce mosquitoes in your yard effectively without having to use spray. So with these results, it makes me think a lot of people will come to me, and come to our volunteers and say, “Oh, this company stopped by and said they're eco-friendly, so they must be safe to use.” Is that true? Is there such thing as an eco-friendly spray for mosquitoes?

Aaron: Yeah, so often two things can be true when this kind of eco-friendly claim is being made. Sometimes these companies that spray more, these conventional products— pyrethroids—will claim that it's green or derived from flowers because they're chemically very similar to pyrethrum, which is derived from chrysanthemum flowers, but pyrethroids are synthetic versions that are made in the lab to be more toxic and to last longer. So sometimes they'll make claims about something being green and derived from flowers when they are still spraying these conventional sprays.

Aaron: Sometimes companies will also spray like essential oils, like garlic oil and peppermint oil, and things like that to kind of try to serve as a mosquito repellent. And I don't have a great sense of the efficacy of these, you know, I've done some research. These essential oil products aren't subject to the same regulation that conventional pesticides are. So toxicity testing isn't required for them at all. But then also it's harder to kind of find reports on their efficacy. And, you know, best I can find is, you know, it might provide some very short-term kind of repellency, but that's not going to last very long. And like you said, Rachel, mosquitoes just fly in from other places. 

Aaron: And we do know that these sprays, these essential oils, some of them can be moderately toxic to bees—in particular larval bees—but then they also potentially can serve as a deterrent for bees as well. So flowers that are sprayed with these essential oils, you might not see pollinator visitation for a few days because pollinators don't want to kind of come at them. So to answer your question, I don't think that these natural sprays are necessarily kind of the magic solution that's both going to get rid of your mosquito problem, but then also be safe for pollinators.

Aaron: You know, for mosquitoes—and again, I've talked about it in the last episode I was on, so everybody can check that out—but really the most important thing is source reduction, which is just removing standing water from your yard, because that's what mosquitoes need to reproduce. Yeah, single most important thing, most effective thing you can do. Mosquitoes can reproduce in the amount of water that's in a bottle cap, and they only need eight to 10 days to go through their life cycle. So any little bit of water you have hanging out in your yard for just over a week can become a mosquito breeding site. So really important to go around your property, your yard, wherever it is that you live, and just make sure you don't have standing water.

Aaron: And then, yeah, as we were talking about—mosquitoes are mobile, [they] can fly. So talk to your neighbor, see if they'll reduce their standing water, as well, so you don't just have mosquitoes coming in from next door. And I guess I should also note, too, that another really important and very effective thing is just personal protection. It might sound simple, but simply wearing long sleeve clothing when mosquitoes are out, using some sort of a repellent, making sure your window screens are intact so that mosquitoes can't get into your house or apartment—really important. And if you do want to use your porch or patio and mosquitoes are out, just setting up a gentle fan will keep them from biting you because they're pretty weak flyers. So that wind will simply just kind of blow them away. So personal protection is also really important—both for nuisance mosquitoes, but then it can also be really important for when disease prevalence is higher as well.

Matthew: So, really there's a lot of things that we could be doing beyond spraying.

Aaron: Yes. Beyond spraying, yeah.

Matthew: Yeah, that's great. Thank you, Aaron. This has been great. As we said before, we were really eager to hear more about this study because we knew you'd been doing it. And so to have heard so much about how the study was put together, and what the findings were, and what the implications of it has been really great. So thank you so much for making the time to sit down and talk with us about it.

Aaron: Yeah, thank you for having me, Matthew.

Matthew: Yeah, of course. And so we’ve got to the last bit and we have our two key questions that we like to ask everybody. And the first one is: if you could see any bug in the wild, what would it be?

Aaron: You know, that's a great question. And like thinking on this a little bit, I think my answer would be those like mound-building termites. I don't even know like the species name. I know some live in Africa, some in parts of Australia, but I think both at the individual level, it would be so cool to see those structures that they make up close. I also think that social insects are really fascinating. So I think that would be really cool. But then I've also—like on the landscape scale, I've seen like photos in Australia where they're kind of like dotting the landscape of these mounds. I think that would be, I think that'd be pretty neat.

Matthew: Yeah, they are.

Aaron: You've seen them?

Matthew: Yeah, when I lived in Kenya.

Aaron: Oh, of course. Okay, very cool.

Matthew: There was some just around one area of the forest, but not everywhere because I think you need the right kind of soil to be able to build that big old mound.

Aaron: Totally.

Matthew: I don't know. I don't know enough about them, but they're pretty, pretty incredible, so.

Aaron: That's awesome.

Matthew: Yeah.

Rachel: Well, I get to ask the last question, and this one is one of my favorites. What is your favorite experience with an invertebrate?

Aaron: That's a really good question. I mean, I've had a lot of nice experiences with invertebrates, you know, having worked with them for years. I would say maybe seeing a Karner blue butterfly for the first time. They're a federally listed endangered species. I think—wait, are they endangered or are they threatened?

Matthew: They’re protected.

Aaron: Protected, yeah, thank you. But I did a year as an AmeriCorps volunteer my first year after undergrad, and I was the Karner blue butterfly site steward for a state park in upstate New York. And I was like in charge of restoration for the butterfly habitat. But unfortunately, the butterfly habitat was also where everyone in the town like took their dogs to run their dogs off leash. So there was a lot of conservation challenges. So I spent like a year of doing like invasive removal, like outreach, telling people nicely not to run their dogs off leash. But I would also do these like butterfly survey transects by myself and, unfortunately, never saw a single Karner blue butterfly at the site.

Aaron: But then I did get to go help—like later in that internship, I helped a New York state biologist with some surveys elsewhere. So I actually got to see them, and it was like a really fun aha moment. It was like a really moist summer morning, and the lupin were like all dewy with little drops of water. And then there was like the little blue butterflies and I was like super, super stoked—it was fun. I have heard that sort of since then, that site at the state park, butterflies have been spotted. So I like to think that I was helping lay the groundwork with, you know, some of that work with no butterflies present, but who knows? Haha.

Matthew: Oh, definitely. I think you can certainly take some credit for that.

Aaron: Yeah, sure.

Rachel: Well, thank you so much for sharing about the study, and sharing your stories. I really love those last questions, and getting to know people a little bit more, and what inspires you, and just some of the experiences you've had. So thank you so much for all the work that you do to help protect our planet and protect these really important species.

Aaron: Thank you both so much.

Rachel: Thank you, Aaron.

Matthew: Yeah, thank you, Aaron.

Rachel: Bug Banter is brought to you by the Xerces Society, a donor-based nonprofit that is working to protect insects and other invertebrates—the life that sustains us.

Rachel: If you’re already a donor, thank you so much. If you want to support our work go to xerces.org/donate. For information about this podcast and for show notes go to xerces.org/bugbanter.