The 3 Best Pieces of Mosquito Control Gear for Your Patio or Yard of 2022 | Reviews by Wirecutter

2022-05-21 22:15:45 By : Ms. Daisy Wang

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We’re currently testing the Thermacell LIV, a system consisting of multiple repellent units controlled via an app.

We’ve added details on the LIV to the What to look forward to section.

To keep mosquitoes away from your deck or patio without slathering your skin in bug repellent, get the Thermacell E55 Rechargeable Mosquito Repeller. After spending 55 hours researching a category full of marketing hype and debunked methods (including popular options like citronella candles), we found that the E55 stands out by actually being effective. Its rechargeable five-and-a-half-hour battery lasts long enough to odorlessly keep a bedroom-sized area mosquito-free for an entire evening—as long as there’s no breeze.

With a rechargeable-battery fuel source, a longer-lasting repellent supply, and a simple interface, the E55 is easier to use than other spatial mosquito repellents.

In addition to the E55 Rechargeable Mosquito Repeller, Thermacell makes several other effective spatial repellents (mosquito-control methods that cover an entire area instead of just one person), but none can match the E55’s ease of use. Its simple interface and rechargeable lithium-ion battery make it much more convenient than butane-cartridge options. It comes with a 12-hour repellent cartridge, but 40-hour cartridges are also available. Compared with other methods of mosquito control, the E55 is more effective and more user friendly overall. This pick replaces the Thermacell Radius Zone Mosquito Repellent Gen 2.0, our previous pick. The two models are similar, but the E55 has a larger coverage area plus a more intuitive interface, and it’s typically less expensive.

The MR450 is more rugged and portable than our pick, and it’s better for situations like camping or sporting events, but its butane cartridge isn’t as convenient as a lithium-ion battery.

*At the time of publishing, the price was $30.

If you prefer a more durable and portable option, we like the Thermacell MR450 Armored Portable Mosquito Repeller. Like the E55, the MR450 has proven mosquito-repelling capabilities, but it lacks some of the E55’s finer touches, particularly the rechargeable battery and the long-lasting repellent cartridge. Instead, like most of Thermacell’s models, the MR450 runs on a butane cartridge and uses four-hour repellent pads, both of which are less convenient than the E55s’s features. The butane is easier to burn through and harder to replace, versus simply recharging a battery. The pads last for far less time than repellent cartridges, and it’s harder to tell when they’re used up. In a large catalog of similar Thermacell products, the MR450 stands out with a more rugged design and a few minor convenience features, but if you’re okay with the compromises of using butane and pads, Thermacell offers similar models worth considering.

These inexpensive mosquito coils work as well as our picks, but they’re not as portable, versatile, or durable. And unlike our picks, their burning ends release a smoke that has an odor.

*At the time of publishing, the price was $10.

For a less expensive option, we recommend Pic’s Mosquito Repelling Coils. Like the Thermacell options, the coils effectively clear an area of mosquitoes, and for their five-to-seven-hour burn time, their price is a fraction of that of our other picks. But they’re not as portable or durable as our picks, their burning ends are not as safe to leave unattended, and they emit a smoke with an odor that some people find unpleasant.

The catch with any of these spatial repellents is that they lose efficacy in breezy conditions. But they’re still your best bet since many other popular mosquito-control methods—including bug zappers and citronella candles—don’t actually work. A few additional methods of mosquito control are worth considering, including simply running a fan, and of course, using the most predictably effective option, a spray repellent in conjunction with permethrin-treated clothing.

With a rechargeable-battery fuel source, a longer-lasting repellent supply, and a simple interface, the E55 is easier to use than other spatial mosquito repellents.

The MR450 is more rugged and portable than our pick, and it’s better for situations like camping or sporting events, but its butane cartridge isn’t as convenient as a lithium-ion battery.

*At the time of publishing, the price was $30.

These inexpensive mosquito coils work as well as our picks, but they’re not as portable, versatile, or durable. And unlike our picks, their burning ends release a smoke that has an odor.

*At the time of publishing, the price was $10.

While researching this guide we spoke with Joe Conlon, then the technical advisor of the American Mosquito Control Association, a position he held from 2000 to 2020. Conlon’s experience with mosquitoes is wide ranging and has spanned nearly four decades. Since 1981 he has been a medical entomologist, and in that time he has presented more than 350 invited papers on vector control to various universities, medical and public-health associations, and national, regional, and state mosquito-control groups. In addition, he has conducted vector-control operations or on-site consultations in 34 countries. He has published at least 20 articles on vector control in refereed journals and more than 70 articles in trade publications.

For questions on repellent safety and the EPA’s pesticide approval process, we spoke with Lawrence Feller, a consultant who assists companies with the development and approval of EPA-regulated products. Feller is also a contributor to the Insect Repellents Handbook. He spoke with us on behalf of Thermacell, one of his clients.

We also read as much as we could on mosquito repellents, traps, and other control products, focusing our attention on information from the AMCA as well as a number of studies, such as several found in Acta Tropica, the Journal of Insect Science, and the Journal of Medical Entomology.

Everyone should have an interest in avoiding mosquito bites. According to the Centers for Disease Control and Prevention, “Vectorborne diseases are a large and growing public health problem in the United States.” This category includes diseases transmitted by mosquitoes, such as West Nile virus and Zika. As we found in research for our guide to the best bug repellent and confirmed again in the research for this guide, the best course of prevention is to use an effective spray repellent.

This guide is for those times—the many times—when covering yourself head to toe in bug spray isn’t practical. We wanted to find a product that would effectively reduce mosquito bites when you’re hosting a backyard barbeque, lounging on the patio, or having a picnic in a park. Most people occasionally want to enjoy an outdoor space without being bitten, and without having to deal with applying a spray repellent—our objective for this guide was to find something that would make that possible.

Spatial repellents, like all of our picks in this guide, are effective in still conditions but basically useless if it’s windy. The AMCA’s Joe Conlon told us, “There is an effectiveness there, as long as you’re not sitting in a place with a stiff breeze.” Think of the dispersed repellent as if it were smoke, and you can visualize how it can simply blow away. This drawback also means that a spatial repellent is not a good choice for someone in motion—if you’re taking a walk in the woods or mowing the lawn, a spray repellent applied to your body and clothing is more effective. The good news is, mosquitoes are weak flyers and have a hard time flying into even gentle breezes—which is why we list a simple room fan among other options you might consider.

When you’re looking at our selection criteria for these devices, it helps to understand how the leading scientists in the field view the problem of mosquito control. One point that the AMCA’s Joe Conlon stressed in our interviews was: “People have just got to understand that there’s no easy solution to this whole thing.” Mosquitoes are famously resilient, and with nearly 175 species recognized in the US alone, there is a lot that people don’t yet know about their behavior. Add in the variables of the local environment where a spray, repellent, pesticide, or any other product is in use, and it’s easier to see why there isn’t one single solution that works 100% of the time in 100% of the possible environments.

With that in mind, though, we identified a few attributes that an effective mosquito-control product should ideally have. After poring over the research, talking to Conlon, and setting our expectations realistically, we settled on a handful of objectives we wanted our recommendations to meet:

Offer proven effectiveness: The product needs to have proven efficacy based on a credible study—preferably more than one. Conlon warned us against relying on anecdotal evidence when evaluating options: “You can’t take internet testimonials at face value. Period.” We found many well-marketed products with positive reviews whose effectiveness has been completely (and repeatedly) debunked by the scientific community. “There is a lot of nonsense out there,” Conlon told us. And as the authors of a Journal of Insect Science study write, “the most egregious danger to the consumer is the false comfort that some repellents give them protection against Ae. aegypti [mosquitoes] when they actually offer none.” In our research, this concern allowed us to eliminate a number of popular control methods, including citronella candles, anti-mosquito bracelets, and sonic options.

Repel rather than trap: Repelling mosquitoes produces more consistent results than trapping them. As the AMCA website notes, studies on traps have yielded mixed results.1 Conlon told us that with current trap designs, if given the choice, a mosquito will always head toward a human over the attractant in the trap. “If you put one of these things in your yard, if you happen to be between the breeding habitat and the mosquitoes, you’re going to get fed upon. They’re not going to bypass you and go to these traps. And they’re going to keep coming.”

A study in Acta Tropica looked at three different traps and found that they “either significantly increased or had no effect on the biting-pressure at short distances compared with the unprotected control.” So traps may even work to bring more mosquitoes to the area.

Keep the balance: We looked at products that had as little impact as possible on honeybees, moths, butterflies, and other positive or neutral insects. Many options, such as foggers, yard sprays, and bug zappers, offer proven effectiveness against bugs, but they kill indiscriminately. During our interview, Conlon told us this kind of wholesale insect destruction could have a ripple effect: Not only are “many of these insects ... beneficial predators on other insect pests,” but you’re “going to kill food that is generally reserved for birds and bats.”

Along the same idea of keeping a balance, the introduction of new animal predators likely doesn’t yield significant results. Bats are the most commonly cited animal option for mosquito control. When we asked about them, Conlon told us, “Absolutely, they’ll eat mosquitoes. But can they survive on eating mosquitoes? Only if you’ve got an enormous mosquito population.” He added that bats tended to eat moths and june beetles instead. “I’m not going to say that people shouldn’t use bats, but if they think that putting a bat house in your backyard is going to solve your problem if you’re living next to a salt marsh, you’re kidding yourself.”

Be practical: We decided that our recommendation needed to be easy to use, safe, and affordable. Price was far less important than effectiveness, but we still looked for something we could simply set out, turn on, and expect to do its job while we ignored it. Even as we came across mosquito traps that cost upward of a thousand dollars, we didn’t enforce a strict price cutoff, but we did hope that we could find a pick that could work effectively for an initial (and ongoing) cost we could actually see ourselves paying. Evaluating that cost for each option, we compared the amount against what we knew about the relative effectiveness of spray repellents and their costs, versus the value we’d place on a more convenient alternative.

Our criteria steered us toward a group of products known as “spatial repellents.” These devices are basically diffuser units that emit a repellent into the air, creating a bug-free zone that repels bugs (rather than killing them), and many of them happened to be affordable and widely available. To shop for spatial repellents, we checked the best sellers on the Amazon, Home Depot, and Walmart sites, as well as outdoor retailers like Bass Pro Shops, Cabela’s, and Dick’s Sporting Goods. In addition, we tested a pack of mosquito bracelets and downloaded a sonic repeller app. At Conlon’s suggestion, we also tested the efficacy of a Vornado 630 Medium Air Circulator fan, Summit’s Mosquito Bits, and Philips 60-watt bug light bulbs.

Considering what our research showed about the variations in mosquitoes from location to location and species to species, we determined that there was no test we could perform that would produce consequential data regarding the effectiveness of a repellent; we relied on established studies for that. So our testing was more about getting a sense of what these products were like to use, as we took them out nightly for three weeks to a back patio in mosquito-ridden rural New Hampshire and on a three-day July camping trip in Maine. There, we simply lived with them, taking note of their ease of use, durability, and projected long-term costs, as well as factors such as how long they would stay on at a given time before needing a resupply of repellent or fuel, which ones burned themselves dry if you forgot about them, and which ones were safest around kids and pets, plus other observations that anyone buying one of these items for the first time would want to know.

With a rechargeable-battery fuel source, a longer-lasting repellent supply, and a simple interface, the E55 is easier to use than other spatial mosquito repellents.

The Thermacell E55 Rechargeable Mosquito Repeller is the most convenient, easy-to-use spatial repellent we found, and it’s nearly as good at stopping mosquitoes from bothering you as a full application of a spray repellent. Compared with similar designs, the E55 is easier to refill and recharge, longer lasting, and more convenient to live with, and it doesn’t present the hazards that some other options do. It won’t stop every single mosquito from getting you, its coverage area is limited, and it loses efficacy in windy conditions—but all spatial repellents share those flaws. This is a new pick for 2021, replacing our previous pick, the Thermacell Radius Zone Mosquito Repellent Gen 2.0. The E55 differs from the Radius in that its interface is simpler and easier to use, and its coverage area is larger.

The principle behind the E55 is simple: The device generates heat to vaporize a little vial of liquid repellent, which slowly disperses out of the unit, protecting an area from mosquitoes and other biting insects. In use the E55 is silent and odorless, and although a small amount of vapor is visible when exiting the top, it visually dissipates quickly.

Other products (including many from Thermacell) do similar things, but what’s unusual about the E55 (and its predecessors, the Radius and Radius 2.0) is that its heat source runs on a rechargeable lithium-ion battery. The battery holds a charge for about five and a half hours and can operate while charging (with the included USB/outlet adapter cable). All of Thermacell’s non-battery models (including our runner-up) vaporize repellent using a butane cartridge or the fuel tank of a camp stove, which means you need to monitor the supply of both the repellent and the fuel source. With the E55, as long as you place it near an outlet and you have a repellent cartridge handy, you’re all set.

According to Thermacell, the protected area of the E55 is 400 square feet or so, about a 20-foot square. During testing, we observed roughly this range in still conditions. This coverage area is quite a bit larger than that of Thermacell’s Radius 2.0, which has an advertised coverage zone of 15 feet (which comes to about 175 square feet). The enhanced effectiveness of the E55 is the result of two factors: First, Thermacell told us in an interview that it had redesigned the heating process of the E55. Second, the repellent cartridges use a higher concentration of active ingredient (5.5% metofluthrin compared with 4.0%). The cartridges are all compatible between the E55 and the Radius models, and it’s confusing to identify which is which—so when you’re buying replacements for the E55, it's important not to get the ones labeled “Radius.” Instead, choose the refills that are labeled Thermacell Mosquito Repellent Refill. If you already own a Radius, the good news is that you can purchase E55 cartridges and see increased effectiveness out of your unit; you don’t need to go for a full upgrade. Note that E55 replacement cartridges are available only in a 40-hour size; although the E55 comes with a 12-hour cartridge, they are not available for individual sale.

Because these cartridges are clear and the repellent is in liquid form, you can easily monitor the remaining repellent. With the other Thermacell models, such as the MR450, our runner-up, and the MR150, you need to watch the color fade from the repellent pad, which is tedious and inconclusive—we were never sure when the effectiveness started declining. The Off Clip-On was even worse in that regard, giving absolutely no indication of the remaining repellent. Unlike with those other options, you can simply set the E55 out and know that it’s working, which allows you to spend less time swapping out repellent, worrying if it’s going to run out, or wondering if it’s out already (as you get eaten alive by bugs). We compared the active ingredients of the repellent cartridges and pads, and you can read our findings in the section about the effectiveness and safety of Thermacell repellents.

The single-button interface of the E55 is simple and intuitive. Press the button, and the unit turns on and begins warming up, its four small indicator lights showing a chasing pattern. Once it is heated and emitting repellent, the four lights remain on. A quick press of the button shows the remaining battery charge on a three-light scale, and a longer press of the button shuts the unit down. Thermacell’s other battery-powered spatial repellents, the Radius-series models, have an automatic timer and shutdown feature; it’s nice to have, but it’s also difficult to manage with the single-button interface, and you have no way to know where the unit is in the allotted time, so we rarely used it.

We also like the overall design of the E55. It’s small and sleek, and it fits right in with some of the more stylish essential oil diffusers we’ve seen. It’s also available in a variety of colors (black and blue), with others exclusive to Home Depot (haze). Overall, however, it’s not very durable, and if you’re looking for something more portable for outdoor activities, we recommend the Thermacell MR450, our runner-up pick. Compared with options such as mosquito coils, the E55 has a safety advantage around pets or small children, simply because it doesn’t put any exposed hot (or burning) parts within reach. But like any spatial diffuser, it is not recommended for use indoors.

The biggest downside to the Thermacell E55 is that it loses its effectiveness in any sort of wind. However, all similar spatial repellents share this flaw, and mosquitoes struggle similarly in the wind.

The E55’s performance in our tests was not perfect, as our sources predicted. We found that even after 25 to 30 minutes of the E55 being active, an occasional mosquito would land on us and take a bite. The conditions at the time were mostly still, though a slight breeze did pass through from time to time. Whether the few mosquito bites were the results of the wind’s interference or just the general limitations of the E55, it proved Joe Conlon’s point that there is no silver bullet when it comes to controlling mosquitoes.

The E55 is designed for mosquitoes, so you may not see a huge reduction in other flying pests. Thermacell told us that more robust bugs, such as horseflies, can be affected by its spatial repellents, but because they’re less susceptible to the small amount of chemical repellent in the air, they may be able to fly into the protected area and get a bite in before absorbing enough to be prompted to go away.

The usefulness of the E55 is more limited than that of some other options we tried. Considering the way the cartridge sits loosely inside and the top stays on with magnets, it’s a tabletop-only item. For any kind of outdoor activity—such as camping, fishing, hunting, or attending a sporting event—the more durable MR450, our runner-up, is a better option.

The E55, like all spatial repellents, also needs time to start working. It typically takes around 10 to 15 minutes for the repellent to “saturate” an area. After we learned this, we got in the habit of putting it out on the patio a few minutes before going out there ourselves.

Finally, there are long-term costs to consider, as with most spatial repellents. In addition to making the initial investment, you need to purchase cartridge refills. If you were to use it roughly three days a week, two hours each time, and an additional five hours on weekends, you’d need a new 40-hour cartridge every month. At roughly $20 per cartridge, these added costs are high, but not out of the range for effective spatial repellents. The butane-powered Thermacell models, which aren’t as convenient to use, work with 48-hour refill packs of butane and cartridges that usually cost around the same.

The MR450 is more rugged and portable than our pick, and it’s better for situations like camping or sporting events, but its butane cartridge isn’t as convenient as a lithium-ion battery.

*At the time of publishing, the price was $30.

The Thermacell MR450 Armored Portable Mosquito Repeller offers effectiveness similar to that of the E55, but with a slender, rugged design and a belt clip, it’s also more portable and durable. The drawbacks of the MR450 involve its repellent pads and its heat source. Instead of a rechargeable battery, this model uses a butane cartridge, which is less convenient. The pads are good for just four hours, a tenth of the E55 cartridge’s 40-hour lifespan, and unlike with the E55 and its liquid cartridges, on this model it’s difficult to gauge how much repellent remains in the pad. We like the MR450’s tough versatility, but there’s no reason to dismiss several similar butane-based options from Thermacell that may meet your needs better; all of them essentially work the same, and compared with the E55, they all lack the conveniences of a rechargeable battery and a clear repellent cartridge.

The MR450 starts up with a few clicks of a button, and a little light goes on when the area is sufficiently saturated with repellent. We liked the light because it allowed us to tell at a glance that the unit was on. Thermacell’s other portable units lack this feature, and its presence lessened the chances of our leaving the unit on accidentally—an easy mistake that can waste a repellent pad and drain a butane cartridge.

The MR450 is built like an oversize remote control, and we appreciated its easy portability and increased durability over the Radius. The rubber overmold looks designed to take a tumble, and the belt clip on the back is a nice touch, likely to be useful for anyone who hunts or fishes (remember, it’s for stationary activities only). While wearing the MR450 on a belt, seated, we did notice that it heated up enough to feel through a T-shirt—not enough to burn, but pretty warm.

The repellent pads of the MR450 are good for only about four hours each, in contrast to the 40-hour cartridges of the E55. The pads come out of the package bright blue, and as you use them, they slowly turn white. Once all of the color is gone, the pad is done. During use, it’s hard to gauge how quickly the pad is fading, which is especially important once the repellent gets very low; you’re basically guaranteed to either change out a pad before it’s truly expired or to use an expired one for too long. We much preferred the E55’s and Radius’s clear liquid vial, which allowed us to quickly and easily determine how much repellent was left and when to reach for a new cartridge.

The heat for the MR450 comes from a small, replaceable butane cartridge, not a lithium-ion battery, and it has a 12-hour life. The timing does sync up with that of the four-hour repellent pads, and refill kits are available with three pads and one cartridge. But it is too easy to leave the unit heating once the repellent pad is expired, which throws that coordination off. The butane cartridge is another thing that needs to be on hand in case you run out. Also, if you spend a good amount of time outdoors, you have to swap out the repellent pads quite often, more than once a day, even. The upside of the butane cartridge is that it’s more portable for camping and other outdoor activities in places where outlets to charge a model like the E55 are scarce.

The MR450 typically costs a little less than the E55, and its long-term costs are slightly lower (though still in the same ballpark). The price difference is not enough to make this model a better value than the E55.

Like the E55 and all other spatial repellents, the MR450 has a hard time keeping an area protected in any kind of wind. It does use a different type of repellent, which we compare in detail in our section on the effectiveness and safety of pyrethroid repellents.

These inexpensive mosquito coils work as well as our picks, but they’re not as portable, versatile, or durable. And unlike our picks, their burning ends release a smoke that has an odor.

*At the time of publishing, the price was $10.

For similar mosquito-repelling effects at a far lower price, we like Pic Mosquito Repelling Coils. When ignited, these coaster-sized spirals slowly burn down like incense. This releases smoke containing a pyrethroid (the labeling on some Pic coil packaging says the active ingredient is “Pyrethrins,” while other Pic labeling names allethrin specifically) that creates an area protected from mosquitoes, similar to the Thermacell products. Like our pick, these coils offer proven effectiveness as a spatial repellent. They’re a fraction of the cost of any Thermacell offering, and they have no fuel or battery that needs monitoring. But there are some key differences between coils and our other picks: Some people find the smoke’s strong odor unpleasant or irritating, the burning ember at the tip can be a safety issue, the coils can drop ash as they burn, and they’re not as portable or durable as our picks.

The Pic coils are inexpensive and long lasting. In our testing, each one lasted about seven hours. In comparison, similar Off coils cost more and lasted only about five and a half hours. The higher cost of the Off coils is due in part to the fact that each comes with a small tray to catch bits of ash as the coil burns down. With the Pic coils, you need to put your own small plate underneath to catch the ash—a minor inconvenience we thought was worth tolerating for the Pic coils’ lower price and longer-lasting effects. If you're feeling fancy, you can use a Pic-branded mosquito coil burner. We've tried one; it works, looks nice, and includes four coils to get you started.

The coils’ smoke and odor were the main reasons we chose a smoke- and odor-free Thermacell product as our main recommendation. Although some owners say they like the smell of a mosquito coil’s smoke, others say they don’t, and we found it unpleasant (it can leave a taste in your mouth and irritate your throat, too).

The fire hazard of the coil’s burning ember is a factor you don’t have to worry about with the Thermacell E55 or MR450, especially if you need to leave your repellent unattended for a bit. For some people, this isn’t an issue, but if you’re in a fire-prone area or if you have kids or pets around, it’s a significant drawback.

The ash, the smoke, and the weaker durability of coils relative to our pick together make the Pic repellent less portable and versatile than a Thermacell option. We chose Pic’s coils over several similar coils because they had a slight edge in price and because they seemed less fragile than competitors, as some owners who have used multiple coil types claim. We have no reason to believe that one of these coils performs better than another coil with the same active ingredients while both are ignited.

Metofluthrin and allethrin, the active chemicals in the Thermacell E55 and MR450, respectively, are both pyrethroids, based on a compound found in the chrysanthemum flower. (Permethrin is also a pyrethroid.) Numerous studies have demonstrated their effectiveness at repelling mosquitoes when used in a spatial repellent, and both chemicals have undergone thorough vetting by the EPA and other regulatory agencies around the world and are deemed safe for this intended use.

The E55 uses metofluthrin, which the Journal of the American Mosquito Control Association found to be “highly effective at repelling mosquitoes.” In the Proceedings of the Fifth International Conference on Urban Pests (subscription required), researchers write: “Results demonstrate that metofluthrin treated emanators are effective at repelling mosquitoes under outdoor conditions.” (At least one author in both of these studies is associated with Valent BioSciences, a company that develops pesticides.)

Allethrin has received similar accolades.2 A study published in Acta Tropica, a journal of infectious diseases, compared a number of mosquito-control methods and found that the three tested diffuser-style repellents, including a Thermacell model, “significantly reduced the biting-pressure … when positioned at short distances from a volunteer.” Of the three tested spatial repellents, the Thermacell was the “most effective.” Another peer-reviewed study from the Journal of Medical Entomology (and partially funded by Schawbel Corporation, Thermacell’s parent company), “showed highly significant protection provided by the TMR [Thermacell Mosquito Repellent]” against two species of mosquitoes and sand flies.

Thermacell provided three other sets of test results to us.3 One, conducted in Costa Rica by the US Department of Defense, found that the tested Thermacell unit was “very effective in protecting persons up to 25 feet away from the unit from attack by phlebotomine sand flies, mosquitoes, culicoides outside in Costa Rica.” A second study, done by the Walter Reed Army Institute of Research, indicated that the tested Thermacell repellent was “very effective in preventing mosquitoes (primarily anopheles sinenis) from entering military bunkers.” The organization Scientific Coordination (on behalf of Thermacell) studied the Thermacell repellent’s effectiveness against black flies in accordance with EPA protocols and concluded that the Thermacell repellent was “surprisingly good against the notoriously persistent attacks of black flies.”

Both chemicals, in their pure form at high, regularly administered doses, have shown toxicity to lab animals, but spatial repellents like our picks use a diluted version that then vaporizes into the air in an outdoor setting. Joe Conlon, writing about repellents and pesticides on the AMCA website, notes, “The dosages at which these products are legally dispensed are at least 100-fold less than the point at which public health and environmental safety merit consideration.”

The EPA has stated (PDF) that metofluthrin “is practically non-toxic to mammals and birds,” even though it is “highly to very highly toxic to aquatic animals and insects.” The EPA approves of its use in a spatial repellent, in spite of its risk to aquatic life, because in vaporized form it’s “not expected to have a high aquatic concentration.” The report does caution that metofluthrin can “pose a risk to non-target insects.”

“The dosages at which these products are legally dispensed are at least 100-fold less than the point at which public health and environmental safety merit consideration.” —Joe Conlon, technical advisor, AMCA

In the same fact sheet, the EPA classifies metofluthrin (PDF) as a neurotoxicant and potential carcinogen.4 This concern stems from studies showing tumors that appeared in the livers of rats, but only when researchers gave them extremely large doses of undiluted metofluthrin regularly over an extended period of time. Again, this kind of dosage has very little relationship to what you could potentially absorb while sitting near a Thermacell E55 or Radius unit.

Use a fan: Moving beyond chemical and spatial repellents, the AMCA’s Joe Conlon told us that using a simple fan, such as our pick in our guide to the best fan, is an easy, low-tech way to keep mosquitoes away, due to the fact that they’re such weak flyers. Conlon told us, “There is no scientific data that I’m aware of that has ever tested that out to find out how many cubic feet per minute you need to keep mosquitoes at bay, but I think most people would agree that if you’re outside sitting on a porch and you’re in 15-mile-per-hour winds, you’re not getting bitten by mosquitoes.”

As for placement, Conlon recommends keeping the fan low, below table level, because the specific mosquitoes that spread Zika (of the species Aedes aegypti) “tend to prefer the lower extremities to bite” and “like to hide underneath outdoor furniture.” Obviously, using a fan is not compatible with using the Thermacell E55, but there’s no reason you couldn’t combine fans with a personal application of an effective bug repellent on a breezy day, in a larger open space, or in other situations where the E55 won’t work for you.

Start at the source: If you have an obvious source of standing water near your home, such as a birdbath or a water feature, you can use Summit’s Mosquito Bits to kill the mosquito larvae. Conlon told us that the toxin involved is released only at the pH level found in a mosquito’s gut; it’s harmless to people, fish, and animals.

Prevent attraction: Last, Conlon recommended bug bulbs, which have a bright yellow hue. The color of the light doesn’t repel mosquitoes, but it doesn’t attract them, either, as a regular bulb might. We tested some, and although the color looks dramatic on the bulb, the actual light is only a little warmer than that of a regular bulb.

Citronella candles, like the Cutter Citro Guard, have no proven effectiveness. In fact, according to the AMCA, citronella candles “do not offer significantly more protection than other candles producing smoke.” A study in the Journal of Insect Science “found no indication that such candles repel Ae. aegypti females.”5

We don’t recommend foggers, like the Burgess 16443652N Propane Insect Fogger, or bug zappers, like the Flowtron BK-15D Electronic Insect Killer, because of their indiscriminate killing of bugs both positive and neutral. Bug zappers in particular are nearly useless when it comes to controlling mosquitoes. According to the AMCA, a Notre Dame study showed that after a season’s worth of bug zapping, only 4% to 6% of the bugs killed were mosquitoes.

Mosquito traps are another category that doesn’t live up to the marketing claims. The AMCA’s Joe Conlon told us that traps, whether propane-based like the Mega-Catch Ultra Pro 900 and Mosquito Magnet Patriot Plus​ or UV-based like the Katchy Insect Trap, “will capture mosquitoes, there’s no question about it, but they’re not as attractive as humans are.” A study published in Acta Tropica showed effectiveness only when four traps (the roughly $400 Blue Rhino SV3100) were set up in a perimeter fashion.6

A number of products rely on sound to repel mosquitos. The only problem is that there is zero evidence that they work. Conlon, writing for the AMCA, notes, “At least 10 studies in the past 15 years have unanimously denounced ultrasonic devices as having no repellency value whatsoever.” We asked him about this, and he told us, “I could send you pictures of sound producers that have got mosquitoes standing on them.” A Cochrane review from 2007 backs Conlon up on this assessment, finding “no evidence to support their promotion or use.”

Another popular item with minimal, if any, effectiveness is a bracelet that has been impregnated with a natural repellent. A study in the Journal of Insect Science states: “Although the active ingredients in some bracelets may be mosquito repellents, we hypothesize that the concentrations that are emitted by all of the bracelets that we tested were too low to have an effect.” In our interview, Conlon told us, “They appeal because you put a bracelet on and you’ll never have another bite forever. That sounds appealing, but it’s ridiculous.” He continued, “If you’ve got a bracelet that’s got mosquito repellent inculcated into it, you’re not going to have mosquitoes laying on the bracelet—but 3 inches away from the bracelet, you’ll have mosquitoes landing. That’s just the way it is.” There is no reason to believe that similar products, such as Buggy Bands patches, would work any better than a bracelet.

We’re in the process of testing the Thermacell LIV. The LIV is a large-scale Thermacell system designed to protect a wide area from mosquitoes. It consists of multiple repellent units, wired together and controlled with an app or via smart home integration. The app can be used to schedule the repellent units, check the remaining levels of repellent, or to set the units on a timer. LIV is currently available in kits of either three, four, or five repellent units.

Thermacell has two other battery-powered spatial repellents, the Radius and the Radius Gen 2.0. These are nice models, and they’ve both been picks previously, but the E55 has a larger coverage zone and is easier to use and better looking.

Thermacell also offers a wide variety of butane models like the MR450. Handhelds such as the MR150 are not as robust as the MR450 and don’t have the indicator light. Other tabletop units, such as the Thermacell Patio Shield Mosquito Repeller and the Patio Shield Metal Edition, use butane and are larger and more conspicuous than the E55.

In addition, Thermacell has designs that incorporate a battery-powered lantern. These models use repellent pads and butane cartridges, as our runner-up does. It’s safe to assume they have the same mosquito-repelling qualities as the MR450, but they also have the same downsides as other butane-powered units—namely, the short-duration repellent pads and the potential for wasting fuel.

The Thermacell MR-BPR Backpacker does not use butane; instead it attaches to a camp-stove canister. This design sidesteps some of the hassle of the butane cartridge, and it would likely work well if you’re at a campsite, but outside of that environment a camp stove is not a convenient fuel source for most people.

Off Mosquito Coils demand a larger initial investment than Pic coils and don’t last as long. They come with a small metal dish to catch the dropping ash, but we preferred just using our own dish with the less expensive and longer-lasting Pic coils.

The idea behind Off Clip-On Mosquito Repellent is very similar to that of the Thermacell models except that this design uses a little fan, rather than a heat source, to disperse the repellent (metofluthrin). The downside, we found, was that it made a little whirring fan noise that sometimes chattered when we moved the unit. It offers some effectiveness in keeping mosquitoes at bay, but a study from the Journal of Medical Entomology showed that its effectiveness “was not sustained at distances greater than 0.3m from the device.” It typically costs just under $10, making it one of the least expensive options; the long-term costs are low, as well, with refills lasting up to 12 hours (this Off model also takes two AA batteries, which you need to factor into the costs).

The AMCA website explains, “The process of a mosquito questing for a blood meal involves a complex, interconnected cascade of behaviors, each probably having its own cues, be they visual, thermal, or olfactory. The complexity of these questing behaviors may account for the bewildering variations in trapping efficiency noted for certain species of mosquitoes at different times, seasons and places. With 174 species of mosquitoes currently recognized in the United States, this is no small issue and will require many years before research can provide a clarification.”

According to a 1956 article in the Journal of Organic Chemistry, allethrin was developed in the late 1940s and is considered a first-generation pyrethroid. Metofluthrin is much newer. The primary difference between the two is that metofluthrin vaporizes much more easily: Allethrin needs a butane heat source to vaporize, whereas metofluthrin can vaporize on its own. This is why metofluthrin works in conjunction with the lower temperature provided by the lithium-ion battery in the Thermacell E55 and Radius models.

These three studies were conducted on behalf of Schawbel, Thermacell’s parent company.

Some people also believe that pyrethroids such as metofluthrin and allethrin may cause allergies, but the EPA looked into the matter in 2009 (PDF) and found “no clear and consistent pattern of effects reported to indicate conclusively whether there is an association between pyrethrins/pyrethroid exposure and asthma and allergies.”

Female mosquitoes are the ones that bite. Also from the study: “The citronella candle combined with a human subject attracted slightly more mosquitoes that the human bait person alone; however, this difference was not statistically significant.”

Conlon also refutes the claims that we found on many trap models: “The ones that purport to keep an entire acre mosquito free, that’s complete nonsense. Those are extrapolations from caged studies that are done in small tented areas where mosquitoes can’t escape.”

Doug Mahoney is a senior staff writer at Wirecutter covering home improvement. He spent 10 years in high-end construction as a carpenter, foreman, and supervisor. He lives in a very demanding 250-year-old farmhouse and spent four years gutting and rebuilding his previous home. He also raises sheep and has a dairy cow that he milks every morning.

by Christina Williams and Wirecutter Staff

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