Three Strategies We Use to Kill Mosquitoes When Working Outdoors (2024)

Mosquitoes are the bad guys of summer. Gals, actually. It’s only female mosquitoes that do the dirty work of biting people. They can wreck a camping trip, cookout, or an outdoor workout. A mosquito bite can be mildly annoying and itchy, or it can sicken you and be life threatening. At least ten illnesses are attributed to these insects. The tiny winged creatures have bedeviled the human race for ages. Thousands of years ago, the ancient Greek historian and geographer Herodotus said, Egyptian fishermen could only escape the swarming pests at night by sleeping under their fishing nets, draped over them like a tent. As somebody who’s tested outdoor power equipment for this magazine and website for several decades, I’ve swatted and cursed mosquitoes countless times as I waded into thick weeds and woods to perform our tests. I’ve evaded skeeters to one extant or another but never employed a fishing net.

What I’ve learned by trial and error is to mount a multi-layer defense. I explain this below. But in order to put this advice to work, first you have to know the enemy.

Mosquitoes find you by both sight and smell. The National Institutes of Health and Maryland’s Department of Agriculture (mosquito control division) both recount in chilling detail how these insects go about their blood-sucking work. No creator of a horror film could conceive of a menace as efficient and deadly as the ordinary mosquito. First, they see you from a distance but they find you by smelling the carbon dioxide you exhale–literally this is a mosquito-guiding plume of human exhaust. It helps the insect bear down on you with the unerring precision of a smart bomb. As the insect comes in for a strike, it smells the lactic acid in your breath and the oily secretion of sebum on your skin that evaporates into the air with your sweat. The lactic acid and sebum help confirm to the insect that it’s in for a tasty blood meal.

Once they land, the little devils get further confirmation because they have taste-sensing receptors all over their body: on their proboscis (the snout-like tube through which they draw blood), on their feet, their antenna, and the area near their mouth. In your imagination, you can see a mosquito licking its chops.

The last step before drawing blood is for the insect to use its thermal receptors to locate capillary veins in your skin. With capillary confirmation, it wastes no time getting to work. It stick its proboscis through your skin, piercing a capillary. Its saliva (mosquito spit) contains an anti-coagulant that prevents your blood from clotting, enabling a rapid withdrawal by means of a bio-mechanical pump in its head. Once its abdomen is full of blood, the mosquito lumbers down the runway strip that is your arm, face, scalp, or other appendage, and flies off. Adding injury to insult, its saliva also contains histamines, a chemical that binds to receptors on nerve endings in your skin. Your body’s reaction to this histamine is a localized widening of blood vessels which leads to inflammation, and a slight burning sensation—an itch. You scratch the itch, which causes a mild pain sensation; in response, your brain releases serotonin, the body’s pain reliever.

And there you are, with a red welt. Meanwhile, the mosquito with an abdomen full of your blood hurries off to hide somewhere and rest while using your blood protein to produce eggs, to produce more mosquitoes, to bite more people.

To break this blood-sucking cycle you need to evade, confuse, and confound these insects. We prescribe a multi-layer defense, as outlined below:

• Layer 1: The first layer of defense is to disguise the odor on your skin and on your clothing.
• Layer 2: Use emitters that block your odor or that release pyrethroids that kill mosquitoes or discourage them from landing.
• Layer 3: Use control measures around your home.

Layer 1: Repellents on Your Skin and Clothing

We’ve seen that mosquitoes smell you. So it makes sense to use repellent that masks your odor while repelling insects. Broadly speaking, there are two kinds of repellents. Those that block your odor and those that are insecticides (they can kill a mosquito that lands on you and they make your or your clothing inhospitable to them once they land). We list three of these below.

The most common form of mosquito-repelling insecticide are pyrethroids, chemicals that are either derived directly from the chrysanthemum flower (Pyrethrum) or artificially created but chemically like Pyrethrum. These are Permethrin, Resmethrin, and d-Phenothrin.

DEET

At first glance, the Journal of Vector Ecology at the Wiley Online Library doesn't seem like a publication that has anything to do with controlling mosquitoes, until you learn that the “vector” is any insect that bites and can spread disease, particularly mosquitoes. The Journal describes the long road that the US Army has taken to protect its soldiers from insects, going all the way back to the Spanish American War. In 1900, pioneering doctor Major Walter Reed (built on the previous work by Cuban doctor Carlos J. Finlay) proved that mosquitoes transmit yellow fever. There is a straight line from that research to studies conducted by the US Department of Agriculture (USDA) in collaboration with the Army to develop various chemicals to repel biting insects. All of this was a result of the sickness and deaths of US soldiers in many far-flung places in WWII, but particularly in Africa and the South Pacific. The research effort culminated in the development of DEET, patented in 1946 by USDA scientist Samuel I. Gertler and approved for public use in 1957.

DEET is not an insecticide. It doesn't kill mosquitoes, but how and why DEET works is still something of a mystery. It’s thought that it may be effective by several different means: it masks human odor, it makes humans taste less attractive and confuses mosquitoes’ taste receptors and smell. For a truly deep dive on the topic, click here.

My experience as a product tester doesn’t extend to testing bug repellents, but I can tell you from extensive first-hand experience that DEET-containing sprays are extremely effective. The one time that I forgot to apply it before running a chainsaw test, resulted in my receiving a tick bite so severe that it took a doctor and a scalpel to get the insect out of my leg.

Suffice it to say, I use DEET-containing repellent on my exposed skin. Higher concentration formulas provide longer-lasting protection, I’ve found. But their smell is also objectionable. I usually apply DEET on my skin using a spray or liquid. When I’m in a severely bad mosquito area, I thoroughly fog my work pants and work shirt with the chemical and let them dry completely before putting them on. I try to do this the day before I go to work. This is traditional all-cotton work clothing (DEET will damage synthetic fibers). However, it does leave it with an objectionable odor that takes several washings to remove.

I've found the DEET odor to be preferable to mosquito, fly, and tick bites. So I stick with the treatment.

Pyrethrin, Permethrin and other Pyrethroids

If ever there was a group of chemicals that is easily confused, it would be the class of mosquito-killing insecticides chemically related to the chrysanthemum flower. Once dried and pulverized, some chrysanthemums can produce a natural extract insecticide, Pyrethrin. A more widely-used version of these chemicals are those that are not extracts but that are created chemically, or synthesized. These are known as Pyrethroids, such as Permethrin, Resmethrin, and d-Phenothrin. And there are others.

An alternative to fogging clothing with DEET repellent is to use Permethrin spray (or similar product), which has little or no odor once dry, compared to DEET. Also, unlike DEET, Permethrin is an insecticide. These repellent products won’t keep a mosquito from finding you, but as an insecticide it repels mosquitoes in the same way poison may deter any creature. Permethrin turns the insect away after landing on your clothing or it immediately goes to work killing it.

Permethrin-based treatments are effective. The US Army, for example, treats uniforms with it. You can buy permethrin-treated clothing or you can treat it yourself. Laundering diminishes its effectiveness but, by refreshing the treatment, you can extend the garment’s ability to deter bugs

Other Treatments: Picardin, Icardin, and IR3535

Picardin and Icardin are low-odor alternatives to DEET/Permethrin. Both are a synthesized version of piperine, a naturally-occurring chemical found in plants used to produce black pepper. The National Library of Medicine points to Canadian research that shows both have similar effectiveness to DEET in repelling ticks and mosquitoes: “Although there is no evidence that DEET-free repellents are safer, many parents prefer them. Icaridin/picaridin has levels of efficacy similar to DEET in preventing mosquito and tick bites. Although it is widely used in Europe and in the United States, this repellent was only licensed in Canada in 2012.”

After decades of dominating the repellent business, it’s no surprise that other treatments are coming online to challenge DEET. One of them is IR3535. The product was developed by Merck & Co., as a clear and no-odor liquid alternative. Those two properties explain why companies such as Avon market the product as being not just an alternative to DEET; their product package even calls out that it is DEET free. Many people have this sort of lurking sense that DEET and Permethrin based products are toxic, so they see a product like this as a safer alternative.

Layer 2: Emitters and Fans

Emitters

Emitters are small battery or propane-powered devices that heat a liquid producing a pyrethroid vapor or a vapor from botanical extracts. The Amazon emitter shown here and the Craftsman are essentially identical products. Both use Thermacell cartridges with a liquid Pyrethroid repellent in them. The Craftsman uses a 20-volt power tool battery; the Amazon emitter uses a built-in battery. Both work seem to work equally well.

Fans

Lacking an emitter, an ordinary cordless fan produces an air stream that is strong enough that it prevents mosquitoes from flying easily to you. Mosquitoes fly at a relatively slow speed of 1 to 1.5 mph and have great difficulty flying in almost any wind but are completely grounded by wind speeds at or greater than 10 mph. Any cordless fan easily produces an air speed that is several times that. Fans also disperse the carbon dioxide that you emit, making it difficult for these pests to locate you.

Layer 3: Area Control Measures

The final counter measure in mosquito control is to treat the outdoors. You can hire a pest-control service to do this, or you can do it yourself.

Mist systems

Think of these as a lawn sprinklers that apply pesticides. A storage tank and pump dispense insecticides to sprinkler heads that apply the material around a zone, such as a deck, patio, the outlying areas around a pool. We admit, it's heavy handed.

Fogging

This method applies pesticide using a backpack blower adapted to apply diluted pesticide. DIY application methods use a leaf blower converted to apply the material. As a mist, the insecticide may kill insects on contact but, depending on the material you apply, it may also have a residual effect that repels or kills insects over time. Fogging is often referred to as Ultra Low Volume (ULV) application. Scientists and governmental regulators have a different take on it, preferring to limit the term “ULV application” as referring to equipment that can convert liquid pesticide to such a fine mist that it can do so without dilution, while referring to diluted pesticide application as Low Volume or High Volume. You can read more about that discussion here.

Yard Care

Even the neatest yard and surrounding area can harbor hundreds and, in the worst case, thousands of mosquitoes. A neat shrub and a somewhat shaggy shrub can both offer about the same amount of protective cover for all types of insects. Still, on the extreme end of the spectrum, a yard that has reverted to near jungle like conditions will definitely provide more protective cover. So if you do nothing else, keep the lawn mowed, the hedges trimmed, and trees pruned. Even if the difference in mosquito protection is so small as to be nearly unmeasurable, I look at it this way: even if there's one less mosquito to bite you, that's a good thing.

Drain or Treat Standing Water

It’s been the backbone of mosquito control for generations: standing water breeds mosquitoes. It’s a fact that tire swings, toys, a watering can, lawn ornaments, low areas in pavements and lawns, and gutters are some of the common areas that can form a puddle and, hence, a breeding ground. Be ruthless in your pursuit of eliminating standing water. Where you can’t drain it (such as a bird bath) use a mosquito dunk to kill mosquito larvae that form in it.

If you’re concerned about the effect of repellents and pesticides (or their residues) on your health and are equally concerned about byproducts accumulating in the environment, there’s no easy answer. Likewise, it’s the stuff of intense environmental scrutiny and study as to the extent these pesticides kill or harm other beneficial or harmless insects. Just in preparing this small story, we’ve looked at a few hundred pages of literature on the topic of mosquitoes, pesticides, and various environmental side effects. We’ve concluded that there are going to be differing views on the long-term environmental effects of large numbers of people using repellents and insecticides, even comparatively benign ones like Pyrethroids. In general, we can only recommend EPA-registered chemicals for mosquito control. That might not be much to put your trust in, but it’s better than nothing.

Don’t over-apply pesticides. Making the product stronger than its recommended dilution rate only wastes an expensive chemical and contributes to residue accumulating in the environment.

We can also say something that you already know or suspect. It’s possible today’s repellent or pesticide application can become tomorrow’s toxic discovery and a source of class-action lawsuits. So where does that leave us? Entomologists refer to mosquitoes as disease vectors; they are moving sources of disease risk. To the rest of us, they are just annoying pests. You can stay indoors or behind screens for approximately a quarter of the year. Or you can use various repellents and insecticides while accepting the fact that there may be long-term consequences, just as there may be long-term consequences from contracting a mosquito-borne disease.

As it is often said: there are no guarantees in life. There are only degrees of risk which we can try to manage.

If you apply pesticides yourself, first put on appropriate protective clothing (safety glasses, a respirator mask rated for mists and aerosols, long pants, and shirt and gloves). Don’t over-apply pesticides either. Follow the dilution instructions for these materials that you find on their label. Making the product stronger than its recommended dilution rate only wastes an expensive chemical and contributes to residue accumulating in the environment. At the recommended application and dilution rate, any EPA-listed pesticide is more than strong enough to kill insects. Dead is dead. Applying a stronger concentration won’t change that.