Electronic Mosquito Repellers

Ultrasonic mosquito repellers — are they effective?

Abstract

A bibliographic review about the use of electroacoustic devices with alleged repellent action on the females of different species of hematophagous mosquitoes is presented. 16 references conclude that these devices do not protect human beings from mosquito bites . The names of 10 of the devices tested as well as those of 19 of the main species of mosquitoes present in the field tests are mentioned. The mosquito species used in laboratory trials are also listed. These tests have been carried out in very different ecological conditions, from Alaska to Equatorial Africa. It is also stressed out that the high intensity ultrasonic frequencies emitted by some of these devices produces a potentially harmful effect on man.

Key Words
Mosquito control, physical methods, acoustic repellents

The development of resistance mechanisms by many mosquito species to most, if not all, of the chemicals used up to now to control them, together with the pollution that these substances elicit in the environment, have made researchers to search for physical methods to which no resistance will appear and that would be environmentally «clean». Among these are acoustical devices, some of which have been designed as attractants and others as repellers for mosquitoes. Although acoustic attractants have evident theoretical advantages, there is not still a unanimous criterion about their effectiveness in the field. On the other hand, the alleged repellent effects of different commercial acoustic devices have not been demonstrated in research work done in the field and in laboratory conditions.

The aim of this article is to present a bibliographic review about the acoustic control of hematophagous mosquitoes. We consider that this method is still valid as an alternative and in other cases as a complement of other methods used to control these disease-carrying vectors.

All human beings with normal audition detect, the annoying for us, buzz produced by mosquitoes while flying. This sound is the by-product of their wing beat, and its fundamental frequency is in the range between 180 and 800 cycles per second (Hz), varying with species, sex, age and temperature (Kahm et al. 1945, Belton and Costello 1979, Tamarina et al. 1980, Belton 1986, Ogawa and Kanda 1986, Clements 1999). It has been demonstrated that males are attracted by the fundamental frequency of the female wing beat Ikeshoji 1981, Ikeshoji et al. 1990, Clements 1999).

The first field tests done in the World using sound recordings of mosquitoes to attract males were done in at that time swampy area of Havana (Kahn, et al. 1949). These American researchers used the sounds produced by Anopheles albimanus Wiedemann recorded in a disk plate and reproduced in the field in the area of the Husillo Swamp. However, the effective range of this acoustic trap was small, since the increase of sound intensity elicited a repelling effect. On the other hand, the attractant effect was exerted only to the flying males, without affecting those perching in the vegetation.

After this initial trial, various researchers have done experiments on the acoustic behavior of different mosquito species, using the frequencies present in the spectrum of female wing beat. Both in the studies done before 1970 (Wishart and Riordan 1959, Belton 1967), and during the 1980’s mainly in Asia (Ikeshoji et al. 1985, Kanda et al. 1987, Ogawa 1988, Leemingsawat 1989) the aim was to attract the males. As a conclusion about his analysis on acoustic traps, Service (1993) states that it does not seem probable that they will be widely used, because they have a small range of attractancy, they mainly attract males and usually they have to be complemented with attractant odors, as those produced by living animals and carbon dioxide. However, we think that these outdraws do not rule out the possibility of doing further laboratory and field tests to develop acoustic traps for sampling mosquito populations of high epidemiological interest, and consequently applying the needed control measures only at the convenient moments, eliciting the least pollution and mosquito resistance possible.

Another form of using acoustic waves for controlling hematophagous mosquitoes, and that is the main aim of this review, started from an article published in Popular Electronics (Greenlee 1970), in which the construction of a simple electronic circuit that generates a frequency between 2000 and 2500 Hz is described. This signal emitted by a loudspeaker (in the original electronic device an earphone was used) is supposed to elicit repulsion in mosquito females. Greenlee (1970) states that this is an experimental device, and that the author does not offer absolute guarantee that it will avoid mosquito bites. Soon after this, at the beginning of the 1970’s, «Electronic Mosquito Repellers» appeared commercially in the market. Greenlee (1970) does not refer to any scientific result that would support the repulsive effect of the frequency used by his device, which is much higher than that of the wing beat of most mosquito species (Clements 1999).

It is understandable then that these electronic acoustic devices were almost simultaneously tested in different parts of the World: Delaware (Kutz 1974), Alaska (Gorham 1974) and the former USSR (Rasnitsyn et al. 1974). Both in these first field trials, as well as in those done some time later in California (García et al. 1976) and Florida (Schreck et al. 1977) in the USA, in the Canadian provinces of Ontario (Helson and Wright 1977), British Columbia (Belton 1981) and Quebec (Lewis et al. 1982), in the villages of Keneba and Bansang in Gambia, West Africa (Snow 1977) and in the former German Democratic Republic (Iglisch 1983) the results have all been negative, i.e. none of the electronic acoustic devices tested (Table 1) showed a significant decrease of mosquito bites in the people using them. If one adds to these the also negative results obtained in Zaire by L. Cook (mentioned by Curtis and White 1982), then it may be said that the field trials of these devices have been done in very different latitudes and ecological conditions, from Alaska to Equatorial Africa. In these tests hematophagous mosquitoes of different habits and significance as vectors of diseases or that only represent annoying pests for outdoor activities of man, including tourism, have been present (Table 2).

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In the laboratory tests, inseminated females have been used, since they are the ones that bite for blood sucking, thus assuring the development of their eggs. Using the devices mentioned in Table 1 and the mosquito species listed in Table 3, researchers also reported negative results regarding the repellent effect of sound frequencies ranging from 2000 to 6500 Hz on mosquito females.

Besides the already mentioned electronic acoustic devices, in the 1980’s appeared others that emitted frequencies above 20,000 Hz, i.e. above the spectrum audible to man, thus named ultrasonic frequencies. The echolocation calls of many species of insectivorous bats are ultrasonic (Neuweiler 1984), and maybe this fact together with what it is said in the documents of the Patent granted to White (1975) for the construction of an electronic device for insect repelling regarding that mosquito females have antipathy for frequencies between 36,000 and 38,000 Hz, made that the next generation of these devices generated ultrasonic frequencies. Some of these devices have been tested with different species of mosquitoes in laboratory conditions (Table 3), always with results contrary to those claimed in their advertisement (Schreck et al. 1984, Foster and Lutes 1985). Schreck et al (1984) also report that these ultrasonic frequencies do not affect either the behavior of a cockroach species, Blatella germanica.

With the devices that generate ultrasonic frequencies one has to know also the intensity at which they are emitted, since high intensities, above 90 dB SPL (0 dB SPL= 20 µPa), may be harmful to man, whom while not hearing these frequencies, does not avoid them. One of the devices tested by Schreck et al. (1984) emitted intensities above 90 dB SPL.

Another type of electronic mosquito repeller is claimed to «mimic perfectly the sound of dragon-flies, natural enemies of mosquitoes». In this case Schreiber et al (1991) measured that the frequency emitted was 30 Hz, much lower than the minimum frequency reported for the mosquito wing beat (Clements 1999). Schreiber et al (1991) with field and laboratory tests in Florida and Curtis (1994) with laboratory trials in London, England also report negative results of this device in eliciting a repellent effect on mosquito females.

Curtis et al. (1990) and Clements (1999) point out that undoubtedly the wing beat sound made by mosquito females have an attractant effect on males, but that females do not seem to respond to acoustic stimuli. In any case, the great majority of the electronic acoustic devices tested emit frequencies much higher than those of mosquito wing beat, and at least 16 different studies coincide in stating that they were not effective in decreasing mosquito bites in the people using them.

In England two commercial companies were fined for making unfundamented advertisement in announcing their electronic mosquito repellers (Curtis et al. 1994). These authors continue saying that it would be desirable that similar legal procedures were done in those countries in which they are possible, since these companies are not only defrauding considerable amounts of money from the consumers, but they are giving them a false feeling of security that these electronic devices will protect them from diseases transmitted by mosquitoes, such as malaria. Curtis (1994) details the judicial trials that conducted to the mentioned fines, and concludes that electronic acoustic devices are still advertised and even worst, sold claiming that they repel mosquitoes.

In this review article we give 16 direct and one indirect references about the alleged «effectiveness» of electronic mosquito repellers. The data from this scientific literature clearly demonstrate that these devices do not protect the people that use them against the always annoying, and some times dangerous, mosquito bites.

bugjammer.com

Are ultrasonic pest repellers effective?

Unfortunately, the science behind ultrasonic pest repellers is ultra-shaky. Seems like an attractive idea though, right? Just plug a charger-sized device emitting undetectable sound into the wall, wait about 2 weeks, then BAM, your garage oasis is insect and rodent free without the use of chemical pesticides or inhumane traps. Sounds great! Too bad these devices have never been proven to actually work. But let’s take a look at the theory anyway.

Ultrasonic sound waves have a frequency higher than what human ears can hear, but invading species can detect them. The sound is meant to irritate pesky critters and prevent them from making homes near the source of the noise. I’m pretty sure this is similar to how I feel about Montreal’s constant construction – in all fairness, I would move away too if I had the choice. But this only makes sense in theory. In actuality some animals seem to habituate to the noise, and others just don’t seem bothered at all.

Image by Cassandra Lee.

Some studies conducted in perfect laboratory conditions show that ultrasonic sound can be fatal to certain species by critically increasing their body temperature or causing audio-induced seizures. So the humane notion of pests simply scurrying out of your garage with a massive headache isn’t quite right either. But due to the variable nature of pest invasions, these findings have not been replicated in actual homes. Researchers using higher quality ultrasound generators have shown that sound can be effective at disrupting mating or eating habits of particular animals. These generators, however, are several grades above any device available for consumers which can’t replicate the complicated patterns of sound and turn out to be pretty much useless.

Additionally, the studies done on commercially available devices are very limited and often lack a control situation. Thus when some studies show that pest infestations do decrease, they have no way of proving that it was a result of the ultrasonic sound. For these reasons, researchers strongly advise against buying into these devices. There is simply not enough evidence. But this doesn’t stop companies selling these products from making claims. This device – one of many similar models available on Amazon – claims to use “safe & effective technology to extremely irritate rodents and insects thus causing them to run away from your home”. Well, they are definitely right about them being safe, safe for humans and pests alike: don’t be fooled.

“But Linda swears by these devices, she never gets mice”, you might say. Well it’s very possible Linda got very lucky. Pest control is messy and extremely variable between homes, so save yourself the $19.99 on Amazon and try some other old fashioned methods: like endlessly sealing up holes and shaking your fists angrily at the pesky critters.

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www.mcgill.ca

Are Plug-in Mosquito Repellents Safe? An honest review

Mosquitoes, in spite of their minuscule stature, are one of the most dangerous insects on the planet. According to the World Health Organization, there are about 500 million mosquito-related cases reported and more than 2 million deaths annually.

So, are plug-in mosquito repellents safe? There are two types of plug-in repellents; one that uses chemicals that evaporates into the air and the ultrasonic plug-in. Both types are safe to use, as long as it is used within recommended standards. However, only chemicals based repellents are effective in getting rid of mosquitoes.

In this article, you will learn about plug-in mosquito repellents and their variants, which one is actually effective and safe, how dangerous mosquitoes are, and what other options you have to preventing mosquitoes from biting you.

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Table of Contents

What Are Plug-in Mosquito Repellents and How Safe Are They To Use?

With mosquitoes being quite a problem especially for children, parents would take an extra step in ensuring that these pests won’t come in and spread their diseases. The use of repellents have been quite popular in deterring mosquitoes away. So much so that manufacturers have developed ways to repel these insects safely.

This includes an electric plug-in that expels chemicals from a pad or liquid container and one that transmits ultrasonic sound that is said to drive them away.

They are both relatively safe to use around children and pets, but the effectiveness of ultrasonic plug-ins are quite questionable.

Ultrasonic Plugins

These devices claim that high-frequency sound repels insects and rodents. But based on hundreds of unhappy customers, buying these plugins to get rid of mosquitoes and other pests would be a complete waste of money.

Chemical Plugins

Leading pesticide companies have developed plugins that contain Prallethrin to kill the mosquito. Prallethrin is a pyrethroid insecticide that is effective in killing mosquitoes. This chemical has a low toxicity effect on mammals and is safe to use around babies, pets, and even pregnant women.

To use the product you must:

  • Remove the cap off the bottle and screw it onto the heating unit. In other cases simply place the pad onto the heating unit.
  • Plugin the unit into an electric socket, and switch on the unit. A light indicator will tell you that the product is on and working.
  • Switch the unit off when it is no longer in use.

To effectively use this product, you must be sure that there is no furniture blocking it and that doors and windows are kept closed.

Choosing to use a chemical mosquito plug-in repellent is quite effective in keeping mosquitos away. They are not toxic to humans and get the job done. Unfortunately, there are no chemical plugins available at this time. It seems ultrasonic plugins have taken over even though they are not proven to work.

Mosquito Intro

Mosquitoes have been around for millions of years. There are about 3,500 species of mosquitoes currently existing in our world today. The females of most of these species have proboscis or tube-like mouths that can pierce through the skin of their hosts.

They consume blood which ideally contains the nutrients they need to produce eggs such as protein and iron. Therefore, only the female mosquitoes actually bite humans, male mosquitoes get their nutrients from plants.

Adult mosquitoes are ¼ inches in length and have a narrow body and wings for flight. They are mostly gray in color with accents of white, silver, green, or blue. Some species have striped legs and abdomen.

The mosquito goes through four phases in their entire life cycle:

Where do mosquitos live and breed?

The first three phases of the mosquito life cycle occur in water and last typically for two weeks depending on the species and season.

The female adults choose to lay their eggs around the edges of stagnant water or attach their eggs onto aquatic plants. This is why, part as a precaution, families in tropics are advised to clear puddles around their homes to prevent mosquitoes from breeding.

Interesting fact, there are some species of mosquitoes that breed in saltwater, though they do not pose an immediate threat to humans.

Here are examples of other breeding grounds for mosquitoes that should be checked for stagnant water:

Bird Baths

If you are fond of having the birds around your garden, you may have a birdbath around. Be sure to empty or clean out the bath regularly. This reduces the chances of any eggs and larvae from forming. One of the easiest ways to keep mosquitoes from breeding in your birdbath is by keeping the water moving. Mosquitoes breed in stagnant water not moving water.

Flower Pots

There are two things wrong with this; one is that you are overwatering your plants; secondly, you are creating a breeding ground for mosquitoes. Be sure to water your plants with just the right amount of water.

Gutters and Downspouts

Often neglected, these parts of our homes are usually clogged with all sorts of dirt, leaves, and grime. This eventually blocks the passage of water during rain, and it collects it instead. This creates a large home for the mosquito larvae to thrive in. Clean out your gutters especially during rainy seasons.

Rain Barrels

Although collecting rain is great, it does come with a major downside. Providing a great breeding ground for mosquitoes. A simple solution to prevent mosquitoes from breeding in your rain barrels is to use a fine mesh netting attached firmly over your barrel. This would stop mosquitoes from even reaching the water as well as having the added benefit of keeping debris out.

Garbage Cans After Rain

Another area that is often ignored is garbage bins. These bins will eventually collect water after the rain, and where there is stagnant water, there are mosquitoes. If the bins are empty, be sure to invert them in order to avoid the collection of water. If there is garbage within them, cover it up to avoid getting mosquitoes in.

Garden Decor

Mosquitoes would only need a few millimeters to nest, making garden decor with crevices that can hold water after rainfall a perfect place for them to lay their eggs. It is advisable to keep these decors under shaded areas to avoid rainwater from collecting on them or clean them out after.

Fishponds are not that much of an issue, especially if you have live fish living in them. The fish will definitely start eating the larvae.

See also:  Joint Statement on Mosquito Control in the United States, Mosquito Control, US EPA

These insects are very active, the go around looking for food from dawn till dusk, but there are some species that are known to be night feeders. Mosquitoes don’t sleep like humans or other animals, instead, during the times they are not active, they rest in an inactive state and come out when it is time to feed again.

However, mosquitoes hibernate during colder seasons, and they stay in protected areas to avoid the extreme cold which will cause them to die, however, their eggs can survive the cold and just hatch when the weather gets better.

How to Eliminate Mosquito Larvae in Stagnant water

The best time to kill a mosquito is when it is still a larva and there are two great products that will help you in your goal of ridding your family of this pest: Mosquito Bits and Mosquito Dunks.

pestcontrolfaq.com

Ultrasonic Mosquito Repellers

The convenient, pocket-sized, battery-powered hoax

I like to think that I’m a reasonably open-minded person—neither credulous nor rigidly skeptical. When a friend of mine told me he saw ghosts, I didn’t try to convince him he was hallucinating; I believe that he had some sort of genuine experience for which the terminology and imagery of “ghosts” provided an appropriate description. I would be reluctant to say that what he saw were really spirits of the departed, but then, things are frequently not what they seem; lacking solid evidence one way or another, there’s no point in being dogmatic.

There are some things, though, that lots of people persist in believing in the face of serious counterevidence. I am speaking, of course, of the decades-old meme that you can keep mosquitos away by using a little electronic gadget that emits ultrasonic sound. Let me get straight to the point: they don’t work. They have been scientifically proven not to work again and again over a period of quite a few years. Yet somehow manufacturers keep making them and people keep buying them, because the claim that they should work seems so plausible (and because they get an astonishing number of fake 5-star reviews on Amazon). As a public service, then, I’d like to tell you the truth about ultrasonic mosquito repellers.

Animal Magnetism

I have always been popular with the girls—female mosquitoes, that is. I don’t know if it’s my charming demeanor or the irresistible smell of Earl Grey tea on my breath, but somehow, if there is a single mosquito buzzing around a crowd of a hundred people, it always manages to find me. My skin is quite sensitive to mosquito bites, too; they turn into big, ugly, insanely itchy welts that don’t go away for days. Fortunately, I live in an area where there are relatively few mosquitoes, but when I’m in, say, Costa Rica in the winter or Saskatchewan in the summer, mosquito avoidance is always a top priority. If I’m staying put, tactics like mosquito netting, citronella candles, and mosquito coils work well, but when I’m moving around there’s no good choice but to cover myself with some sort of mosquito repellent. DEET-based repellents, while effective, are greasy, smell horrible, and supposedly find their way into your bloodstream quite quickly, where they can’t be especially healthy. Newer, more natural alternatives are safer and less offensive to the senses, but it’s still no fun to smear the stuff all over my exposed skin (and keep reapplying every hour or so).

So one summer, I bought myself an ultrasonic mosquito repeller. The package claimed this tiny, battery-powered device was “safe and effective,” and I figured it was worth finding out if I could get relief without all the chemicals. When I took the device out of its package, the first thing I noticed was that it had not only an on-off switch but also a frequency dial. I thought that was odd; wasn’t it supposed to be some precise frequency that drove mosquitoes away? But perhaps I was just thinking about the device in a technologically unsophisticated way.

I took the repeller outside and went to an area that I knew to be popular with mosquitoes. I flipped the switch, and within a few seconds a mosquito approached me, hovering about a foot away. I slowly turned the dial from one frequency extreme to the other; the mosquito was unfazed. I thought it was perhaps a question of range, so I held the device as close as I could to the mosquito. Even an inch away, it had no effect. Finally the mosquito landed on the little black box in my hand and I decided the experiment had been definitively concluded.

Sales Pitch

The U.S. Environmental Protection Agency and numerous universities have performed tests to determine if or how well various ultrasonic repellers work. In most cases, the tests showed no difference between using the device and using no protection; in the least successful experiments, use of ultrasonic devices increased the number of bites. And the U.S. Federal Trade Commission has clamped down on manufacturers making unsupported claims about these products. So what makes people think they should work, and why don’t they?

Some animals are sensitive to sounds pitched higher than the range of human hearing; ultrasonic whistles are used when training dogs and circus animals, for example, and bats use echolocation to navigate and hunt. The theory behind ultrasonic mosquito repellers is that there is some frequency, or range of frequencies, that mosquitoes can hear—and find distasteful enough to stay away from. For example, some manufacturers claim their devices mimic the sound made by a male mosquito’s wings, the theory being that females who have already mated would try to stay away from them (though it turns out they do not). Others say their devices emit sounds at the same frequency as the wing beats of dragonflies or bats, the mosquitoes’ natural enemies. Unfortunately, the sounds made by dragonflies and bats have no effect on mosquito behavior in the real world. They don’t prevent mosquitoes from becoming lunch for their predators, and they don’t protect you from becoming dinner for the mosquitoes.

Ultrasonic mosquito repellers do one thing remarkably well, however: survive. They have maintained their uncanny ability to transfer money from the pockets of consumers into manufacturers’ bank accounts in the face of terrible odds. Alas, this is a meme that deserves to die. Save your money and rent a copy of The Sixth Sense or The Mosquito Coast.

Note: This is an updated version of an article that originally appeared on Interesting Thing of the Day on July 27, 2003, and again in a slightly revised form on September 5, 2004.

itotd.com

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