THE FIRST ISSUE of “American Gardener,” the newly redesigned member magazine of the American Horticultural Society, arrived recently, and in it are lots of good reads—including an article by Nancy Lawson, a.k.a. The Humane Gardener.
She writes about the folly, and hazard, of falling prey to the promises of those mosquito-control services you’re probably seeing advertised about now—and where mosquitoes fit into the bigger environmental picture, anyhow. (Above, a 1905 illustration of mosquitoes in the Culex genus by E.A. Goeldi; image from Wikimedia Commons.)
Nancy Lawson, whom you may know as “The Humane Gardener”—the title of one of her books—is a naturalist and habitat consultant based in Maryland. Nancy promotes animal-friendly planting strategies and challenges us to sharpen our awareness that we are not alone out there, but actually just one part of a much bigger picture. Nancy’s more recent book is called “Wildscape.”
Plus: Comment in the box near the bottom of the page to enter to win a copy of Nancy’s book “Wildscape” (affiliate link).
Read along as you listen to the May 19, 2025 edition of my public-radio show and podcast using the player below. You can subscribe to all future editions on Apple Podcasts (iTunes) or Spotify (and browse my archive of podcasts here).
mosquito misconceptions, with nancy lawson
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Margaret Roach: I was glad to see what you wrote about in the first of the revamped issues of the American Horticultural Society’s magazine. So that was great to see that they wanted to do that type of a topic. All of these “Got to kill the insect” kind of advertising pitches make me a little crazy, I guess because my name is Roach, huh? [Laughter.] But I love the lead of your story, where you quote some of the advertising campaigns for mosquito-fogging services and stuff that have slogans like, “Outside is fun again,” “The only good mosquito is a dead one,” and then the one, “Kids love butterflies, not ticks and mosquitoes. Battle back to protect your family and pets.” So what do we think of all that?
Nancy Lawson: Yeah. Well, that last one really got me, because there’s a picture with it of two kids, like toddler age, looking with a looking glass into a jar, and there’s a blue morpho butterfly Photoshopped in. The whole thing is Photoshopped, and it’s showing these children just enraptured by insects that don’t even occur here. And then, yeah, it’s all kind of mirage from start to finish, in terms of how they market these services, and make people feel comfortable and safe. And even people who are concerned about local ecologies oftentimes don’t realize because they see these companies as the authority.
Margaret: And I mean, this came up for me when some readers asked me about tick services. “Oh, we’re having this applied to our yard because it’s going to get rid of all the ticks.” And there’s ones with ants [laughter] and do you know what I mean? Spiders! And it’s like, oh my goodness. I mean there’s so many, and these claims: One is more fantastical than another. And a lot of that is based on the fact that they talk about the products that they’re going to use being “natural,” but what they don’t talk about is that they’re not selective. That they’re not just aimed at one species.
Nancy: Exactly. They really hype up that their product is—they say it’s pyrethrins, which is chrysanthemum-derived, which is also very harmful; it’s a broad-spectrum insecticide anyway, even though it’s natural. But usually they’re not even using that. They’re using the synthetically produced version of that, which are pyrethroids, and they’re structurally just much more toxic and longer-lasting. So they’re marketed to last weeks at a time, up to three weeks.
And so those companies will say, “Well, we’re only targeting vegetation where the insects are.” “We’re only spraying when the bees are not out.” It’s early in the morning or late in the day or something like that. But as we know, first of all, there’s tons of nocturnal insects, crepuscular insects, and there’s lots of insects during the day that are nocturnal that are roosting in the same vegetation that mosquitoes do, like fireflies.
And when I interviewed Aaron Anderson at the Xerces Society for that article, he gave the really good example of a leafcutter bee who’s going to one of those treated areas to cut a piece of a redbud or a piece of a Virginia creeper or a rose or some of these plants that they love, and taking it back with them to their nest. So it’s not only potentially harming the adult, but also the larvae, because there’s still that chemical on that leaf for potentially weeks at a time.
Margaret: So this residual effect of these pyrethroids can kill bees, butterflies, caterpillars, fireflies, many other insects. And I believe there’s also some research evidence about potential human impact. So it’s not like these are something that’s good for everybody, all living creatures [laughter]. [Above, a bumble bee.]
Nancy: Yeah, exactly.
Margaret: But this indiscriminate mosquito fogging and so forth, I was fascinated in your article to see that there’s many species of mosquitoes. So a mosquito isn’t a mosquito isn’t a mosquito; it’s not like a one creature. And that only what I think you said, 12 of them, of those 200 [in the U.S.], are the ones that there may be disease issues with. So a lot of mosquitoes we don’t have harm from, any serious harm other than an itchy bite, maybe. But also they’re plentiful and they’re incredibly important in the food chain for a lot of animals, of other insects and I think especially of birds and so forth, who eats mosquitoes.
Nancy: So there’s 3,500 worldwide, and then there’s 200 in the U.S. and outlying territories, and only around 12 are considered to be disease vectors. And so many other ones, they might be “nuisances” to us, but they’re not actually harming us, but they are feeding—all of the mosquitoes are feeding—birds, bats, frogs, dragonflies especially, damselflies. [Below, a common whitetail skimmer dragonfly.]
Margaret: Right. That’s what I was trying to remember, dragonflies; of course, of course.
Nancy: And what I found really fascinating when I wrote this piece was the Boulder example, in Boulder, Colo., of what they’re doing. And they found that the damselflies and dragonflies have really just a huge role in mosquito control at their sites that they monitor. And they had a West Nile outbreak in the early 2000s in that region. And they since then have this really comprehensive program in the city of Boulder, but they do not spray any adulticides. So they’re not spraying, they’re not targeting adult mosquitoes, because really that doesn’t get at the source of the problem.
Margaret: And it’s so costly in other ways environmentally.
Nancy: And so they are monitoring. They have 19 traps around the city, and then they have 300 wetlands that they monitor, and they’ll monitor for a certain threshold of risk. So as long as the number of infected mosquitoes stays below that threshold, there’s a very low risk of transmission to humans.
And so they just spot-treat, but very, very judiciously, with Bti. And that’s that bacterial larvicide [Bacillus thuringiensis subspecies israelensis], which a lot of people will know about, but they spot-treat the larvae with that. And when they find that there’s an area that maybe there aren’t enough predators present, there isn’t enough biodiversity present, and there are I think it was like 10 or more mosquito Culex mosquito larvae in a sample. And the two species in that area that cause disease are two in the Culex genus. And so if they find 10 or more or something in a little sample, then they’ll use some granules of Bti.
But what they found is that surrounding communities that spray actually go sometimes many orders of magnitude above the threshold for risk to humans. And they’re actually spraying adulticides all the time.
And so they were working on, when I talked to them, putting together their data to do a paper on this. And their thought was that there were two reasons: that not spraying kept around all these other mosquitoes that don’t carry disease and that were good competition for the two disease-carrying species. So they take up egg-laying sites, and they also are eating algae as larvae and microorganisms and stuff, and they’re competing basically in the same niche for space and resources. And when you take them all away, then that means that those Culex species can come in and proliferate. And also a lot of those Culex species are more resistant to the adulticides. And so that’s another issue with spraying, is that you’re fostering-
Margaret: There was a line in your article, I think it said it can take a million droplets of insecticide just to reach one mosquito.
Nancy: [Laughter.] That was a Cornell study. So where are all those other droplets going?
Margaret: Well, we know: They’re killing lots of other things. And again, the residual effect for weeks afterward and so forth. And again, important to remember that this, folks, is a food chain. Exactly.
And so again, I don’t love a mosquito bite. It’s irritating. And I want to swat at them, too, when one comes at me or whatever [laughter]. But if you’re going to sit on the patio and have supper, put a fan out. Do you know what I mean? Let’s try to think of other things that we can do to manage some of these situations, rather than assume and buy into the baloney, really, that there is some kind of cure-all. Like, “Hey, don’t worry about mosquitoes. Just pay us the money to do this.”
And I’m sorry to sound full of disdain for some of these promises of some of these programs, but I feel that way because it causes a lot of other harm. And that’s what’s never revealed in the sales pitch, that this other harm is going to cascade down from this action that you’re taking, and the consumer doesn’t understand that. And I think a lot of the consumers, if they did understand that, would maybe try a different approach. And that’s why we’re talking about it today. I don’t think people know that, and I think the advertising promise sounds good, right?
Nancy: Right. And there are people who will push back on the idea because it’s true: birds and bats alone aren’t taking care of mosquitoes. They eat mosquitoes, but they eat a lot of other things, too. But it’s the whole collection of our wild neighbors out there doing the job, and animals like dragonflies and damselflies are eating a lot of mosquitoes. They’re also feeding the birds.
That was another thing in the Boulder research, is that in areas where you’re taking away so many of those dragonflies and damselflies by taking away their food, their mosquito prey, then you’re also taking birds away, because the dragonflies and damselflies are in turn bird prey. And so you’re reducing all the way up the chain the biodiversity, and the many layers of ecological health.
Margaret: And there are things that we can do within our own little habitat, so to speak. And I know people have heard this before, and it sounds maybe tiresome, but it really does make a difference. Standing water, even a very small amount, is a problem, and is a place where this reproduction activity can happen. So you’re inviting more mosquitoes if you leave an inch of water in a bucket or whatever, or again, puddles and things like that.
And even if you don’t rinse your bird bath, that water can become a place where they reproduce. And so we can make a difference in our own immediate surrounding.
I have water gardens, too, water gardens that I’ve had for more than 30 years, in-ground water gardens. And I have seasonal troughs, big troughs of water, that I put out kind of as container gardens, so to speak. But they’re water. And people always, when they come to garden visits here, they’re always, “Oh, you must have terrible mosquitoes.” And I’m like, “No, I can’t remember the last time I got a mosquito bite.”
Now, one thing is I’m an upland site. I’m on a hill; I’m not a lowland site, so I don’t have a lot of large amounts of standing water and things like that. But I do have water and I am in a area where it rains a fair amount and so forth. So I attribute it to the fact that I also have tons of frogs and tons of birds. And I mean, because I invite them all in with other approaches to sort of habitat-style gardening for all these decades, and I think they all help. They’re the helper creatures, because again, it’s a food chain.
Nancy: I get the same comments. And one year in the fall, I noticed in October, I got a few bites. And I realized it was, I think, because the dragonflies were leaving and some of the birds were migrating. [Above, the pond at Nancy’s garden in Maryland; below, a common green darner dragonfly.]
Margaret: So standing water and cleaning our bird baths, not letting water puddle and pool and be in things like containers here and there and so forth, that’s just standing. What else can we do? I mean, I know a lot of people talk about making sort of a bucket trap, and even Doug Tallamy recommends sometimes making a bucket trap filled halfway I think with water and some straw in it and so forth.
Nancy: And then that’s a place where mosquitoes are going to want to lay eggs, and so it’s nice and stagnant. But a lot of people, they will put the Bti dunks in there.
Margaret: This, it looks like a big tablet, like a big giant aspirin or whatever [laughter], but it’s a Bti, it’s this natural insecticide, so to speak, this biologic.
Nancy: Yeah. And so I asked the Xerces Society about it. I’ve always had a concern about that because people will also put it in ponds. They’ll put it in bird baths, and is it really safe for everybody but mosquitoes? How can that be? So I did ask Doug a couple of years ago, because I’m involved with our local Bee City, Howard County Bee City in Maryland, and we were talking about putting together bucket kits. And I had a concern about that, because I had read that midges could be affected, and they’re really good bird food and stuff. And Doug said they wouldn’t be affected probably because they lay eggs in mud in the bottom of marshes and ponds.
But then when I talked to the Xerces Society just recently, they said they just recommend that people instead just do the bucket, just put some straw or some grass in there and some water, and dump it periodically every few days. And don’t use a Bti because we don’t know the effect of Bti on the soil and all the organisms in the soil. And also it does harm crane flies.
And as far as people putting it in ponds and such, I mean, there’s a certain amount of tolerance that we want to have, too. There’s been impact shown on dragonfly and damselfly larvae, but it’s thought to be because they’re being deprived of their mosquito prey when Bti is used. So I think it’s one of those things on a spectrum where-
Margaret: If we don’t need it, we could leave it off the to-do list. And again, if the bucket becomes this kind of funky place with a little water in it and they’re attracted to just the straw in the water, and you dump that every few days like you’re saying, then the eggs never hatch. It’s never left there long enough for successful reproduction, and you skip the Bti. So good. So less is more. I mean, that’s better, safer.
But I do think a lot of us probably have mosquito places where they would like to be, a little bit of water here and there because it rains and you forget there’s your weed bucket that you left out wherever [laughter], by the compost heap, and it has an inch of water. Do you know what I mean? And those are the things and that can contribute to the problem. So these little things that we can do to be a little more vigilant, I think as well.
Nancy: And that is the very Number 1 recommendation.
Margaret: And to me, it’s the same thinking when everyone I know wants a tick formula, to snap their fingers and have it all go away, but it’s vigilance. It’s only vigilance, the scientists tell us so far, we don’t have a magic bullet for ticks. And their populations come and get higher and lower and so forth. But there is nothing that has been shown in research to—no matter what the companies tell you who want to apply some product to your yard or put traps or whatever—that’s going to do the job on a scale, a bigger scale like a whole neighborhood or anything like that. They’re going to be there.
And so it’s like, well, then you know what? It’s my responsibility, especially as a gardener, to be vigilant about my own self-care, right?
Nancy: Yes.
Margaret: Each time I go out and come back in and to have a protocol and to be conscious of it, because I need to protect myself because I can’t, again, snap my fingers or pay someone an amount of money to make it all go away, the danger go away.
Nancy: And it’s definitely understandable that in some areas of the world, in some regions, it’s a bigger concern than in others, and a bigger risk. But for example, where I live, it’s a very low risk of actually contracting something.
Margaret: You mean from mosquitoes?
Nancy. Yeah. And so that idea of a certain tolerance level, too, I mean, no one wants to be bitten, but like you’re saying, you can apply repellents, too, and you can wear long sleeves.
Margaret: And again, if you want to dine outside, put a fan if you don’t have a screen room or something like that to use.
Nancy: The fan is great. Mosquitoes can’t fly on the wind.
Margaret: Right, exactly. So that can be a really good, and it doesn’t have to be on high, either. It can be low, or a couple of little small ones. It makes a huge difference.
Nancy: And you can be outside rather than an hour before and after sunset or when they’re most active, you can be outside at different times when possible. There’s different things that you can do. If you can’t do it all, there’s certain things that you can try.
Margaret: So I just want to ask, let’s talk about something happy [laughter]. What’s exciting going on in your wild world down there in your own habitat, in your Maryland garden? Any projects under way or anything you’re particularly focused on this spring? [Above, a resident frog at Nancy’s garden.]
Nancy: Yeah. Well, I’m getting ready for some tours.
Margaret: Oh, boy [laughter].
Nancy: And I usually cannot see who’s nesting. I can kind of tell where they’re nesting by their activity, but I hate to disturb and look too closely sometimes, because afraid I’m going to freak out the birds. But right now there is a cardinal couple nesting in the coral honeysuckle that’s growing up the staghorn sumac that’s right outside my slider in my office. And it’s so sweet, because I can hear them calling to each other, and I can see her situating herself all day long. And it has made me wonder, do they like this particular place a lot because the flowers look so much like her? I mean, her head has the little red down the back that looks just like… And all the petals are interwoven on the outside of the net. I mean all the flowers. It’s like, I don’t know if they pick them or they fell in, but they’re all on the outside of her nest. So it’s so sweet.
Margaret: Well, I have an irate female robin. I had a garden tour on Saturday and 300 and something people came, and robin was right on the back porch actually in a coral honeysuckle as well, nesting [laughter]. And she was very angry that I allowed visitors in the property at this time. “Margaret, I filed a complaint, Margaret,” she said, so…
Well, I’m always really glad to speak to you, and again, I was really glad to see your article in “American Gardener.” Thank you. And thanks for bringing up this important topic. I hope I’ll talk to you again sooner than later. Let’s not let so long go by.
Nancy: Yeah, thank you so much. I really appreciate you covering this topic too, Margaret.
(Images from Nancy Lawson, except as noted.)
more from nancy, and more on mosquitoes
enter to win a signed copy of ‘wildscape’
I’LL BUY a copy of “Wildscape” by Nancy Lawson for one lucky reader. All you have to do to enter is answer this question in the comments box below:
Even used a bucket with straw, or a Bti dunk, or a fan outside or any other mosquito-managing tactic in your garden?
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MY WEEKLY public-radio show, rated a “top-5 garden podcast” by “The Guardian” newspaper in the UK, began its 15th year in March 2024. It’s produced at Robin Hood Radio, the smallest NPR station in the nation. Listen locally in the Hudson Valley (NY)-Berkshires (MA)-Litchfield Hills (CT) Mondays at 8:30 AM Eastern, rerun at 8:30 Saturdays. Or play the May 17, 2025 show using the player near the top of this transcript. You can subscribe to all future editions on iTunes/Apple Podcasts or Spotify (and browse my archive of podcasts here).
