“Virtually every year, a new product appears on the market that claims to be the answer for the elimination of mosquito nuisance. In nearly every case, the promotion is accompanied by a great deal of advertising, but the merits of the product are rarely backed with scientific testing. The American public has invested billions of dollars in zappers, repellers, and plants that claim they will keep mosquitoes from biting. ”
This quote is from Dr. Wayne J. Crans, Professor of Entomology, Rudgers .
In this post I will review a number of products for keeping mosquitoes away and determine if they work. Unless specified differently, the following quotes are taken from Dr. Crans’ report.
Electronic Repellers
These are small devices that produce a high-frequency sound to repel mosquitoes. Some emit a sound that apparently mimics bats, but bats don’t actually eat many mosquitoes – another myth. If bats don’t eat mosquitoes, why would the sound of a bat scare mosquitoes away?
Other products claim to mimic the sound of a hungry dragonfly. Science has shown that dragonflies don’t scare mosquitoes away.
“Scientific studies have repeatedly shown that electronic mosquito repellers do not prevent host seeking mosquitoes from biting.” These devices don’t work.
The American Mosquito Control Association reports that, “At least 10 studies in the past 15 years have unanimously denounced ultrasonic devices as having no repellency value whatsoever.”
Mosquito Apps for Your Smart Phone
Smart phone apps and YouTube videos copy the electronic repellers and produce high frequency sounds. I have reviewed them in Mosquito Apps for Your Smart Phone – Do They Keep Mosquitoes Away? They don’t work.
Bug Zappers
Bug zappers, like the one pictured above, use ultraviolet light to attract insects, and once they get in the device an electronic charge kills the insect. The loud pop or zap lets you know that another insect is dead.
These things do kill insects. The problem is that most of the dead insects are not pests, nor mosquitoes. Most are night flying beetles and moths. “Biting insects, in general, make up less than 1 percent of the insects killed in zappers.”
Customers like the zapping sound they make and are completely unaware that their device is depleting the population of beneficial insects, which in turn harmss things like birds.
These products should be outlawed.
Handheld Bug Zappers
Rather than use stationary units, you can also get handheld devices that look like tennis rackets and provide an electrical shock through the metal strings. I did not find any serious scientific reviews online, but customer reviews on Amazon are mostly favorable.
“There is something gratifying about the LOUD POP!!! when you hit a fly or mosquito”
“they get stuck in it and a little lightning bolt shines from their bodies”
The device clearly works – it does kill bugs. But you have to chase them around the house to catch them. This might be fun, and good exercise, but I just can’t see going outside in an area with lots of bugs and winning the battle. Is this another gimmicky product that ends up in the tool shed?
Ok, I’ll admit it – I’d like to try one. It does sound like fun.
CO2 Traps
Mosquitoes can smell the CO2 we breath out and fly directly towards us. CO2 traps are devices that produce CO2 to attract mosquitoes away from humans and then kill them. Some devices also incorporate other fragrances, and many use propane to create the CO2.
Jonathan Day, an entomologist with University of Florida had this to say, “The state is home to 74 species of mosquitoes, of which about half prey on people. Only a few species are likely to be controlled with a CO2 trap because variables such as flight range, habitat preference and feeding behavior determine whether the trap will capture mosquitoes in large enough numbers to reduce biting around the home.”
“The traps can be very effective if the target insect is one that doesn’t fly very far or has its breeding site near your home. But most of the mosquitoes people complain about in Florida have flown a considerable distance before they end up in someone’s back yard and using a trap to control them is like trying to capture all the grains of sand on the beach.”
His research has shown that human hosts work much better than CO2 traps.
Another review of these products concluded that, “These traps provided no protection from mosquito bites.”
Other versions of these devices are used by scientists to collect mosquitoes, but that does not make them a good choice for gardeners.
Clip-on Fans
Clip-on fans are small devices that contain a battery, a fan and some insecticide. You clip them to your belt and the fan sprays out repellent into the air around you. It is claimed that the repellent keeps mosquitoes away.
The most popular device on the market is Off Clip-on. The insecticide that it uses is metofluthrin which is classified by the EPA as a neurotoxin and potential carcinogen. This has now been approved by the EPA and some preliminary studies do show that the chemical itself keeps mosquitoes away. According to the American Mosquito Control Association, the testing of the device itself is still underway. If that is correct, we are still waiting for some science to support the use of this product.
The product website warns, “if you move, allow a few minutes for the unit to rebuild its protection.” I wonder if the mosquitoes have read these instruction? Will they wait a few minutes before attacking?
Anecdotal online comments suggest that when you are sitting still in low wind, the Off product does provide some protection. In wind, or if you are walking even slowly, there is no real protection. That should not be a surprise. The device works by filling the air around you with insecticide vapors. Wind or movement disturbs this shield and you are no longer protected, so it is useless for gardeners.
The device uses custom, refillable cartridges that last 12 hours, at a cost of about $5 US each. The cost of using this regularly will be high, not to mention the production of non-recyclable empty cartridges. Why would this product not be designed so that you could recharge it by adding a few drops of liquid pesticide? Why? Because they make their money on selling expensive refills – an example of razor blade marketing.
Just buy some DEET. It is much safer, has been proven safe for many years compared to this recently approved insecticide, and with DEET there is far less garbage to add to the local dump. A $10 bottle of DEET lasts me all summer.
Personal Propane Vaporizers
ThermaCELL is a popular brand of this type of device. It uses a burning propane source to heat a mat containing an insecticide. The heat vaporizes the insecticide and fills the air around the device. They are available in personal carry packs, or as table top devices.
The insecticide used by the ThermaCELL is allethrin, the same insecticide in old fashion mosquito coils. The oral LD50 for allethrin in rats is 1100 mg/kg, which is considered to be slightly to moderately toxic.
One study show that it is reasonably effective, reducing bites by about 93%. Another study by US Navy Entomology Center of Excellence found that ” it reduced biting pressure by 76%.
These devices suffer from the same problems as the clip on fans, namely that they work best when sitting still in a low wind situation. Good for a gardeners relaxation after work on the patio, but not as useful while working in the garden. They also require both propane cycling and chemical pad refills, at relatively high prices.
Wristbands and Patches
Mosquito repelling wristbands offer a simple solution. Wear the wristband, and mosquitoes stay away. Gone are the
sticky chemicals that you lather on your skin.
These wristbands, bracelets or patches are infused with insect repelling chemicals. Many manufacturers try to appeal to those who prefer natural products and as such they contain chemicals like citronella or peppermint oil – marketing calls these “botanical extracts”. Don’t be fooled – they are just chemicals.
A detailed study compared such wristbands to 7% DEET and found that wristbands failed to stop landing by the mosquitoes, while the DEET worked almost 100%. The wristband did reduce the rate of landing but it was not nearly as effective as DEET.
When the wristbands were infused with DEET, they only provided protection around the area next to the wristband. This is no surprise to anyone who has ever used DEET or any other liquid-applied repellent. If you just cover your hands – the skeeters will bite you on the leg and ears. A wristband would never protect your who body.
The US Federal Trade Commission has fined a number of companies for deceptive marketing of their mosquito wristbands.
Vitamin B1 patches offer no protection.
Citronella Plant
I’ve written about this plant before in, Citronella Plant Keeps Mosquitoes Away.
The plant being sold is not the citronella plant, and even though it has a fragrance, it does absolutely nothing to keep mosquitoes out of your garden. It is all false advertising.
Citronella Candles
Citronella oil does keep mosquitoes away, but the amount of oil in candles is extremely small and citronella candles work only marginally better than regular candles – neither works well.
Smoke does tend to keep mosquitoes away, but candles, both plain and scented are almost useless on your back deck.
Bat Houses
It is claimed that bats eat a lot of mosquitoes and therefore having a bat house will help with your mosquito problem. There are two basic problems with this idea.
The first one is that it’s very difficult to get bats to set up residence in a bat house. Commercial products rarely work, partly because they are not made right and partly because bats are choosy about their home.
The second problem is that bats don’t eat as many mosquitoes as you think. The common expression, bats eat 1,000 mosquitoes a night, is a myth. They are just too small for larger bats, which spend their time eating larger insects like dragonflies and moths. Smaller bats will eat mosquitoes but there is no evidence that they reduce local populations.
By all means try to put up a bat house. They need all the help we can give them, but research proper designs and make or buy one that meets their requirements.
Purple Martin Houses
Everyone knows that purple martins eat tons of mosquitoes – or do they? This is a very common myth.
“Proponents of the Purple Martin, cite the oft-quoted statement that a Purple Martin will eat 2,000 mosquitoes a day and up to 14,000 when the insects are extremely plentiful. The quote is based on an anecdotal account in the literature that was based on body weight of the bird and the number of mosquitoes that would be required to sustain its metabolism. Most ornithologists realize that mosquitoes form an insignificant portion of the Purple Martin’s diet and would agree that the birds play a limited role in controlling mosquito populations.”
Manufacturers of purple martin houses use the mosquito control angle to sell their product. Don’t fall for it.
Setting up purple martin homes is a great idea, but they won’t keep you from being bitten by mosquitoes.
What Does Work for Mosquitoes?
You will see from the above list that most mosquito repelling devices either don’t work, or work in a very limited way. So how do you keep mosquitoes from biting?
DEET and Picaridin are still your best choice for both safety and efficacy.
Here are some other posts that might interest you.
Mosquito Repellents – Best Options
Mosquito Apps for Your Smart Phone – Do They Keep Mosquitoes Away?
Mosquitoes Repelled By Fragrant Plants
Mosquito Repellents That Work Against Zika Virus
thank you for citing literature; it is comforting to know that the material is written by a scientist
What do you think about allethrin which is what is used in a Thermacell product?
As an avid camper, mosquito deterrent is an issue near and dear to my heart – and every other part of my body. Skeptically we got a Thermacell 3 years ago. Surprising it works!
The nurseries are loaded with citronella plants. What a b.s
Thanks!
Somebody gave us the tennis racquet one as a joke gift some years ago. It is fun. We use it to attack swarms of tiny flesh biting flies that follow us in our boat on Georgian Bay — tween age boys get assigned the job and do it with gusto.
Not so easy to catch a mosquito but you get a very satisfying spark catching a fly.
The outdoors artist, who is very vulnerable to biting Diptera, goes with “mosquito repellant smeared on my face and hands and a [pyrethrin] insect coil burning beside me.” https://karstaddailypaintings.blogspot.com/2011/06/whippoorwill-country-oil-on-canvas-5-x.html The coil is set a bit upwind, and seems to repel the Mosquitoes rather than killing them.
The coils work to keep them away, provided there is not too much wind, or they are used in an enclosed area.