An interview with experts: Are backyard mosquito sprays safe and effective?

Person spraying pesticides in air
June 1, 2021
  |   33 Comments

We get a lot of questions and concerns about backyard mosquito sprays. We interviewed two experts to learn more about the risks.

Each year, more yards are being sprayed for mosquitos. Did you know you could be poisoning your yard but mosquito populations are not being reduced?

Before deciding to spray your yard, know the facts. Spraying can harm you, your kids, pets and your neighbors. The chemicals can also harm birds and insects that help eat mosquitos and pollinate your yard.

To learn more about the problems with mosquito spraying, we interviewed Deborah Landau, an entomologist and conservation scientist at The Nature Conservancy, and Mary Travaglini, a certified organic land care professional and organic landscape manager at the Montgomery County, MD Department of Environmental Protection. These experts agree: Mosquito treatments, including the alleged “all natural” variety can harm you and your environment, while not actually reducing mosquito populations.

Person spraying pesticides in air

How effective are mosquito sprays?

MT: Published and peer-reviewed research by Professor David Pimentel shows that only 0.1% of the pesticides on average reached the target pests. [Pimentel, Cornell University 1995]. When Pimentel looked specifically at flying insects in the study, like mosquitos, the average was less than 0.0001%, or only one in a million. This is because the droplet size of a pesticide must be small and must float in the air.  The droplet size of a mosquito spray must be so small that the chemicals must float in the air, but they also easily drift out of the target area, killing other insects or mingling into the air we breathe.

DL: Sprays can only kill mosquitos that are in your yard at the time of spraying. Mosquitos typically fly 1-3 miles, so they can quickly re-populate your yard. A commercial mosquito treatment will be more likely to kill butterflies, bees and ladybugs in your yard at the time of application than the mosquitoes you’re trying to get rid of. Mosquitos are most active at dawn and dusk, but mosquito spray companies often come during the day when most pollinators are active.  If the treatments target standing water, beneficial insects that eat mosquitos, like dragonfly larvae, will also be killed. If the spray is focused on wet areas, such as piles of wet leaves, chances are they’re killing far more fireflies than mosquitos. Sadly, birds will often pick up insects killed by insecticides, and eat them or feed them to their young.

Dead bee in a flower

What am I getting for my 300 dollars’ worth of a pesticide spray?

MT: If we turn the .0001% effectiveness into dollars and cents, a millionth of $300 dollars’ worth of spraying is .0003, which is not even a third of a penny. In fact, we’d have to spend $10,000 before we even got once cent worth of value! Spend your time and money cleaning gutters, removing standing water, and getting together with the neighbors to do this throughout the neighborhood.

DL: Over time, mosquitos become resistant to pyrethroids (the active ingredients most mosquito treatments) through gene mutation in mosquito populations. Mutations in just this one single gene are enough to make mosquitos in one area resistant to the pesticides very quickly. Companies that spray on a regular schedule will make your mosquito population become resistant even faster. So essentially, you’ll be left with a yard and neighborhood full of super skeeters.

Mosquito staying dry under a wet leaf

Is there anything I can do to control mosquitos in my yard besides spraying?

DL: If you want more bang for your buck, purchase BTI mosquito dunks; they’re cheap, effective, and easy to use (you just place them in areas that hold water). And these are a bacteria that will only kill mosquito larvae. You should always remove standing water from your yard, including under flowerpots, inside wheelbarrows, and pretty much on anything plastic. Don’t forget to clean out your gutters even in summer (you’ll be rewarded with a dry basement in addition to fewer mosquitos)!

MT: There’s a reason why Disneyland, in a part of Florida with lots of mosquitos doesn’t use pesticides to control mosquitos. They take an approach that neighborhoods, HOAs, and businesses can all use right here—they ensure water doesn’t stay standing long enough for a mosquito to lay its egg and hatch into an adult—which is about 7 days.

Cleaning gutters reduces mosquitos

I still hear about West Nile virus? Is this a concern?

MT: The CDC reported 6 cases of West Nile in Maryland in 2019, and no deaths. In 2018, there were 245 cases of all types of mosquito borne illnesses in Maryland, although it cannot be attributed to whether those were carried in the bodies of visitors or spread by mosquitos in the State. I looked up estimated cancer diagnoses for the first half of 2020, and we’re already at nearly 35,000 cancer cases. I’ll choose long sleeves and clearing standing water instead of spraying chemicals that won’t actually be effective but are a risk to my health.

DL: Prevent mosquito bites by wearing long sleeves and using non-toxic repellents that use oil of lemon eucalyptus (OLE). Data shows OLE-based repellants are just as effective as the synthetic DEET formulations. DEET can be toxic at high levels and can damage synthetic clothing. A fan on your deck can be surprisingly effective – mosquitos are weak fliers, and the breeze from a fan will not only cool you off but will keep them away from the area.

What about the “all natural” alternatives that a company has told me about?

MT: Companies might describe that the chemicals used are derived from chrysanthemum flowers, but they are not from plant extracts. Commercial pyrethroids are synthetically produced to mimic the same properties of the pyrethrins in chrysanthemum flowers. Both chemicals paralyze the nervous system of many insects, but synthetic pyrethroids and the undisclosed chemicals they are mixed with are designed to be more lethal. Pyrethroids are neuropoisons in humans, and can cause rashes, respiratory distress, allergic reactions, headache, nausea, convulsions, and more. The additives can cause a host of other reactions. Pyrethroids are also very toxic to fish and other aquatic life, and spread easily on the wind to neighboring properties and into streams. The chemicals can persist on surfaces for days, further killing insects that come into contact.

MT: I looked up the data from the national poison control centers – over 27,000 calls were placed to poison control in 2018 for pyrethrins and pyrethroids, accounting for over 33% of the pesticide calls to poison control alone! Imagine how many more exposures are unknown.

Child sitting in the grass

Here’s another tip: If you’re looking for a way to reduce the entire population, consider these simple devices called OviTraps—used by the military around the world effectively to reduce mosquito populations. Don’t forget to keep removing standing water from your yard all summer long and remind your neighbors to do the same. Your neighbors, pets, birds, pollinators, fireflies and skin will thank you!

 



33 comments on "An interview with experts: Are backyard mosquito sprays safe and effective?"

  1. Scott Gordon says:

    In Montgomery County a major pest mosquito is the Asian tiger mosquito, an aggressive day biting invasive species. This species often remains in the immediate environment, flying only a few hundred yards, especially when the location provides all of its essential living requirements: a bloodmeal source for reproduction, sugar/nectar for energy, adequate resting sites and available egg laying sites. I agree that there are alternatives to backyard pesticide spraying such as using environmentally friendly alternatives like Bti, but I would not recommend ovitraps for general use. While they are frequently used by scientists as a mosquito surveillance and research tool, they can become a problem if not properly maintained. Ovitraps are small soup-size cans, painted black, partially filled with water and provided with a substrate (wooden paddle or paper lining) on which mosquitoes will lay their eggs. Ovitraps must be inspected and maintained on a weekly basis which includes replacing the egg substrate, dumping out the water and replacing it with new water). Failure to do this maintenance can result the ovitrap becoming a mosquito producer. Any eggs laid on the substrate will hatch when it rains and the new breeding site will attract more tiger mosquitoes. Since ovitraps are often put out in large numbers, a portion often go missing, either through the action of animals or just failure to relocate a trap. Another drawback to ovitraps is that they do not trap and kill the egg laying female mosquito. Since container breeding mosquitoes often practice “skip oviposition” where they lay only a portion of their eggs in any one container, by not trapping the egg laying female the ovitrap at best collects only a small portion of her eggs and she can move on to other sites. A better alternative is the gravid Aedes trap (GAT) which traps the egg laying female on a sheet of sticky paper inside the trap before she can lay her eggs thereby preventing both the next generation of eggs from hatching and removing egg laying females from the population. These traps require no power, use no toxic chemicals, are relatively inexpensive and require very little maintenance. Several neighborhoods in Montgomery County are encouraging residents to join in large scale tiger mosquito control programs using GAT traps. A paper published in Nature in 2018 by Brian Johnson and others “Neighbors help neighbors control urban mosquitoes” describes the results of first 2 years of a control program using GATs in University Park, MD. The paper is open access and available at https://www.nature.com/articles/s41598-018-34161-9

    1. Phil Ueber says:

      Useless information

  2. Richard Kramer says:

    Keep in mind that the Ovitraps are effective for some aedes species as Scott mentions. The problem is with other genera such as culex that have a greater flight range.

    Disney isn’t a good model for residential mosquito management. They control 10s of thousands of acres so they can larvacide and use other methods to prevent larval development – manage the breeding sites ( water) and you control mosquitoes. You can not control your neighbors yards and their breeding sites.

  3. JIM ORISCAK oriscak says:

    ENJOYED READING THIS.. I was not aware of the harm to other insects / birds / humans.. The sellers of the spray product tell you that it is 95 -98 % effective and that there are no harmful effects to humans.. If this is an obvious lie how can they get permits to do it.???

    1. Andy T says:

      This is the new reality … you can lie and get away with it. And when a newspaper, media outlet or article like this one calls you on it, the liar can just say “fake news.”

  4. In one breath you say mosquito treatment only kills what’s in the yard at time if treatment, ignoring fact that insecticide used is residual type, minutes later in sane interview you say chemicals persist on surfaces for days which recognized residual properties but also means it kills future mosquitoes.visitirs not present in yard at time of treatment so…which one is it? This interview is do misleading , almost every sentence is a falsehood. No, mosquitoes don’t develop pesticide resistance in one generation, nature doesn’t work that way, no, droplets don’t need to “float in sir” and no, treatment in sunny time is ad effective if not more as mosquitoes will be wherever the sun is not. Spraying at dawn or dusk us idiotic, you spray not shoot, you don’t need to hit the target, you cost the harborage area and that could be done at 1100 hrs just fine. The don’t hurt the dragonfly by treating standing water advise followed by few n the standing water is pure Saturday night material hehe, As for Disneyland…tjrh have an army if underpaid workers spraying a garlic-infysed solution. Customers will never afford such a bill, besides, using garlic will kill the cats, mice will be delighted hahahahh, not an option for the regular customer. Miss Landau, I am a nice guy, if you need to learn about mosquitoes let me know, no charge. Just stop spooking the public with nicely sounding nonsense

    1. Scott F says:

      So you’re saying these mosquito treatments don’t kill good insects like honey bees, ladybugs, butterflies… etc?

      1. george lemieus says:

        There is no 100% “it doesn’t kill beneficial insects” treatment out there but by not touching blooming flowers risks to honey bees is minimized. Ladybugs…once in someone’s attic then living spaces they are not seeing “beneficial” at all, rather invasive so see, beauty is in the eyes of the beholder. Nothing is bad or beneficial all the time and nothing is safe, problem is with virtue signaling idiots that like to complicate everything with useless ideas/concepts despite having no experience in basically anything except “caring” because caring is easy, requires no money nor effort. Wanna hear something funny? The most “concerned” citizen bending backwards to prove how evil pest control companies are usually live in condos with 1 or zero plants there so I am always on guard when I am questioned by “concerned” citizen especially when they come with loaded questions like yours, like “are you saying alcohol is always good? You know exactly what am I saying, stop wasting my time with gotcha questions.

        1. Lori says:

          So George you are saying it can kill honey bees by saying NOT 100%. We will take that as a yes. The other point you bring up is NOT to let the pesticides touch blooming flowers? Now how exactly are you going to stop a spray/mist from landing on flowers? Huh? Who’s making more sense here? I have made my mind up.
          You’re bullying attitude does nothing but make you look even more suspicious than the ridiculous examples you made.

          1. Miss Lori I don’t get it, if I don’t answer I must be hiding stuff, if I do it is suspicious. Hehe, some people have their minds made up no matter what. Still, let me try again. Wind. That’s how you control where what you spray goes. By paying attention to speed and direction of the wind.

            As for bees nobody likes them and honey, more than me but go ahead paint me anti bee see if I care. I an honest professional and who gets it gets it, who doesn’t doesn’t, my problem. Actually it is, trying to speak common sense gets you in trouble nowadays. .so don’t reply, I won’t even read it, not interested anymore.

      2. Ryan says:

        Mosquito treatments can kill beneficials the same way that cars can kill people. They can, but they shouldn’t. That’s why you need a license to operate commercially. You should know what you’re doing. When bees, for example, are out of their hive in a two to five mile radius, they are working–pollinating. They do not hang out with ticks or adult resting mosquitoes in brush piles and underneath decks and sheds and stone walls. It is all about correctly targeting, and avoiding spraying where the bees do go–blossoms of any kind, whether a petunia flower or a Kousa Dogwood in June. It is absolutely possible to avoid drifting onto blossoms. They literally do it professionally. Used correctly, pesticides should kill the targeted pest. The pesticide application is not the problem. It is irresponsible and uncaring applicators/operators that present an issue. Choose a responsible company. Like with anything else.

        1. Jill says:

          Hi Ryan, my neighbours just had their property sprayed by a company that uses synthetic pyrethrin. It was very windy, I was working in my garden and felt the spray, looked up to see all the mist floating through the trees into my yard. The “licensed operator” also sprayed the trees and bushes on my property that border my neighbours yard, without even asking me. By the time I realized he was spraying my property, not theirs, it was too late. A lot of it is blooming right now, full of insects. I’m feeling devastated that all the work I’ve put into over the years to create a space that is friendly to pollinators and beneficial insects has been wiped out by this idiot. Is it really going to kill the beneficial insects? The company claims it lasts for at least 3 weeks, so is it going to keep killing insects all that time? I’ve been reading a lot about this but it seems like there is a lot of contradictory or biased info.

          1. Water the vegetation. Big time. Insecticide breaks down from sunlight itself, and high temps but there’s a mechanical process to remove the insecticide, pronto. Watering will remove the insecticide present as a dust, instantly. There, problem solved 🤪

    2. Manugian Liz says:

      Mr. LeMieux:
      Respectfully, your website testimonial along with the photo of your employee wearing what looks like a war-time gas mask whilst applying the pesticide speaks volumes:

      “We’re mosquito killers not public relations mosquito awareness advertising extraordinaire experts. Don’t expect us to be preaching about how dangerous mosquitoes are, how they “carry viruses” and all that stuff, we hate them and we kill them but we don’t badmouth them :), we are simple mosquito killers nothing more nothing less.”

      I realize that ignoring the opinion of respected scientists may be self-serving but that may not be the best thing to do for the natural world which we call home.

      1. Miss Manugian, you mention “respected scientists” but .. respected by whom? Do you respect my scientists? Why do you expect me to respect yours? What makes your scientists better? Fact that they agree with your point if view?

        Yes we’re mosquito killers, I would personally rip their freaking wings and necks off if possible and I am sorry if my position offends you but this planet we call home is better mosquito free. Let me know when you want me to spray your backyard unless you want to let mosquitoes eat you alive to, you know, stick it to people like me hahahahh

  5. manish says:

    interesting

  6. Angelica freund says:

    Well of course… they tell you what they need to tell you to get business. Many people have bought into these franchises, up to $20,000 , and what happens to that investment if people realize that the spray is toxic. Just look up on MSDS site or Material safety data sheet. Look up the chemicals Pyrethins and pyrethroids. This is actual scientific data and it’s actually horrifying that the EPA allows this to be sprayed in neighborhoods by inexperienced kids on school break. There will always be someone who twists the truth.
    But these stats dont lie. These are neuro poisons and I have personally experienced the headaches the respiratory distress and more. Causing me to have to leave my home for hours. It’s even more crazy that you can be outside enjoying a BBQ and next thing you know some kid shows up with a loud backpack blower and huge clouds of chemicals are filling the environment. And this is legal. Not even a warning. And epa does not look out for the little guys best interest. Dont believe that for one minute. I do like the article and the good tips about neighbors working together to control with the traps. Maybe not perfect but it sure beats poisoning the environment and those who make their home here.

    1. Ryan says:

      No offense, but you have absolutely no idea what you are talking about. Also, it is just “SDS” no one says “MSDS” these days. Research and design of Pyrethroids dates back to World War II, and they have been modified, applied, and repurposed continually for decades upon decades. They are ubiquitous in our society, being used everywhere from the fabrics industry to products for pets like cats and dogs, where it is rubbed directly into the system of the animal. Pyrethroids are absolutely a synthetically-derived chemical and not a friendly substance–just like laundry detergent is not a friendly substance whatsoever. That doesn’t mean it can’t serve a vital role in pest management in our society. The problem with the umbrella term “pesticide” is that it auto-corrects in our brain to “poison”. It is like the word “drug”. Yes, some drugs are horrible, others practically nothing, and of course there is everything in between. Caffeine is a drug. Cocaine, amoxicillin, vaccines–these are all substances. You have to question what it does and where it falls with regard to safety concerns, but that does not mean you need to categorically push it away–especially the Chrysanthemum plant-derivative.

      There are so many benefits in terminating mosquitoes and ticks and stopping the spread of disease, it is not just about a simple annoyance at a barbecue. The stuff is washed away into the soil where it is broken down by bacteria and gone forever as the substance it once was–we are not talking about C8 here, to say the least. Controlling pests IS in “the little guys” best interest. If you don’t want to utilize substances, then don’t. Stop going to CVS, don’t get a mosquito service–do whatever you like, but just know that some people see an actual value that is real–one which you apparently prefer to just summarily dismiss instead of learning more about it. Go ahead, show me stats on how many people get sick or die–they are probably using it incorrectly. Kids these days will eat tide pods, there is always someone dumb enough to abuse what could otherwise be a valuable asset when used correctly and responsibly.

      1. Hello says:

        These pyrethrums and pyrethroids are highly toxic to cats. Please do your research.

      2. Hello says:

        “Kids these days will eat tide pods“. This is your closing argument for why someone should not be concerned her yard is being filled with toxic chemicals without warning? Can you see how ridiculous this sounds?

  7. Ryan says:

    Why is this article saying that the “all natural” solutions are Pyrethroids? That is bullshit. The natural substances are the ones that are a blend of essential oils, like Essentria IC3 and Tick Killz. Occasionally you find a natural solution based on enzymes. That’s it. Cedar oil does not come from the Chrysanthemum flower. I have three different clients with bee hives ON THEIR PROPERTY and they come back year after year. You think that’s because we smoked their beehive? Seriously? I know that there is no such thing as having zero bias, but this article is more than just misleading–it is downright incorrect, and to tout these opinions as coming from “professionals” means they are either being disingenuous or are simply ignorant, and honestly I don’t know which is worse.

    1. Hello says:

      So, you are in the business of pest control? And you are arguing with an entomologist and conservation scientist at The Nature Conservancy, and, a certified organic land care professional and organic landscape manager at the Montgomery County, MD Department of Environmental Protection? Do you think you may be out of your league?

      1. Dave says:

        You guy are idiots. Zero logic here. Doesn’t matter that you have the title of “scientist”. When you try to argue that you aren’t getting your money’s worth because 100% of the spray is not killing mosquitos, you sound incredibly stupid. You are paying to have the mosquitoes killed. And the spray works. And I get my 3/4 acre lot treated for $79, not $300.

        So much mis information in this article that it could have been written by CNN.

        1. EC says:

          How does it feel to be the type of person who contributes to cancer cases in your area?

  8. Hello says:

    These pyrethrums and pyrethroids are highly toxic to cats. Please do your research.

  9. I really liked your article . I think it was a great post! There is a lot of information in there to process. One thing that stood out for me: It’s important to know that pesticides can harm you, your kids, pets, and other people nearby who may be sensitive or young. Pesticides also kill insects such as bees which pollinate our food supply and help control bugs like mosquitoes.

    1. grtyy53g3y says:

      Dragonflies help control mosquitoes not bees. And “Pesticides also kill insects such as bees which pollinate our food supply” is the most overused sentence, overused in virtue-signaling, look, I care about bees who pollinate our food whua, whua, someone call me a whuambulance 🙂 Pest control techs don’t spray blooming flowers, stop painting us in bee-killing colors already, Jesus, enough already!

      “It’s important to know that pesticides can harm you, your kids, pets, and other people nearby who may be sensitive or young.” is another say nothing but feel good about saying it type of sentence. What about mothers in law, do pesticides harm mothers in law too ?Why not mention it, is always kids and pets and my favorite “loved ones” hahahaha why not mention mothers in law, huh? I HATE virtue-signaling!

  10. Anti-democrats says:

    School them into common sense Dave hahahaha but you are wasting your time, these are the idiots wearing a mask while alone in their own cars with the windows up, you just can’t fix stupid. You tell them global warming is good because growing plant season means more food but no, global warming is bad Antarctica weather is good hahahaha. You tell them by them can’t run to the toilet in time without soiling his panties but no, Trump tweets mean things so Biden is good hahahaha. They tell you insecticide is useless because it doesn’t kill the mosquitoes then they tell you insecticide is bad because he kills everything else, they say police is bad then next day they ask why it’s in police protecting the people hahahah you just can’t fix stupid so have your fun with them but move on don’t expect any results.

    1. The Dave says:

      Your post is so well written that it leaves no room for imagination to manipulate your image.
      These are obviously terrible chemicals, especially if the immensely conservative and industry-at-all-costs EPA is giving warnings about their usage. I’ve gotten the SDS information right from the neighbor’s spray company. They sent it to me in a cheery fashion, as if they were proud. Herein lies one of the biggest issues: they WERE proud, because they had been sold a (b)ill of goods by the petro-chemical industry and it’s White Knight, the EPA. They were told that if they pay money to become licensed, and use these prescribed products, that there isn’t anything that can possibly go wrong. And they believe it.
      And why shouldn’t they? After all, why would the good people at the American Tobacco Institute allow cigarettes to be sold if they would give cancer to their customer base? Why would doctors hand out medicine that is highly addictive and detrimental to your health? Why would the FDA ban glyphosate if Monsato (Bayer) says it is perfectly safe? Why would the Army spray PFAS all over Michigan if it wasn’t safe to drink the water afterwards? It’s the same with the EPA, and petro-chemicals. And make no mistake, there are petrochemicals in these products. Don’t take my word for it, request the info and do your research. We are slaves to the petroleum industry in so many ways beyond our transportation industry, and there is simply too much money on the line to change.
      The apotheosis of the dollar. And I am not immune. I am just as much to blame as anyone else every time I don’t take action against the tide of ignorance that is overwhelming our world. Idiocracy is here. Nothing is sacred, certainly not life on our planet (yes my anti-democratic fellow, that includes human life).

  11. Sylvia Darrow says:

    I use a Mosquito control company.
    I still see many bees, butterflies, and other beneficial insects. My birds and cat are still alive. I have not been bitten once by a mosquito! With the extremely
    Stringent Montgomery County laws,
    I challenge most of this misleading article!

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