Electronic pest control

Electronic pest control is the name given to the use of any of the several types of electrically powered devices designed to repel or eliminate pests, usually rodents or insects.

Numerous electronic pest control devices are readily available throughout the world. Hardware stores and garden centers usually stock some sort of electronic device advertised to repel a variety of pests and you can also find them on the internet. Although these devices have been around for at least 20 years, they have only recently become popular and widely advertised, probably due to their environmentally friendly claims.

There is a wide range of opinion about these devices, some people claim that they work for them, others claim they are not effective at all.

Since these devices are not regulated under the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA), the EPA does not require the same kind of efficacy testing that it does for chemical pesticides.

Types of Devices

There are basically two types of electronic pest control devices widely available, these are Ultrasonic and Electromagnetic.

Ultrasonic devices operate by emitting short wavelength, high frequency sound waves too high in pitch to be heard by the human ear — that is, all frequencies greater than 20,000 Hz. Humans can hear frequencies from 20 to 20,000 Hz but as we age, we become less sensitive to the higher frequencies. (Long wavelength, low frequencies — below 20 Hz — are called infrasound and are also inaudible to humans.)

We can't hear ultrasound because our eardrums can't vibrate fast enough, but some animals such as dogs, bats and rodents can hear well into the ultrasonic range. Some insects, such as grasshoppers and locusts can detect frequencies from 50,000 Hz to 100,000 Hz, and moths and lacewings can detect ultrasounds as high as 240,000 Hz produced by insect-hunting bats.

Insects detect sound by special hairs or sensilla located on the antennae (mosquitoes) or genitalia (cockroaches), or by more complicated tympanal organs (grasshoppers, locusts, moths and butterflies).

Effects on pests

Cockroaches and spiders may initially respond to electronic pest control devices by moving about a bit more than usual, but don't appear overly eager to escape from the sound waves. After a few weeks, they will generally calm down. Rodents adjust to the ultrasound (or any new sound) and eventually ignore it. At best, ultrasonic waves have only a partial or temporary effect on rodents. Numerous studies have rejected ultrasonic sound as a practical means of rodent control.

Tests of commercial ultrasonic devices have indicated that rodents may be repelled from the immediate area of the ultrasound device. Other tests have shown that the degree of repellence depends on the frequency, intensity, and the pre-existing condition of the rodent infestation (e.g rodents will be less eager to leave if they have a nest with young)

Electromagnetic pest repelling devices claim to alter the electromagnetic (EM) field of your household wiring, and vibrate the electromagnetic field that always exists around the wiring in the walls of your house. Electromagnetic fields are present in every appliance that operates on electricity. When an appliance is switched on, a very weak electromagnetic (EM) field develops around the current-carrying wiring in your home.

An Australian test lab looked at the electronics of one of these devices. When plugged in, it generates a pulse in the electrical current (which also makes the little indicator light switch on and off). This causes the electrical current in the house wiring to fluctuate, which in turn makes the EM field fluctuate. This is thought to create an intolerable environment for pests.

However, this device draws only a very small amount of current compared to normal household appliances. Even an incandescent light bulb draws considerably more current than the pest device. This means that the EM field strength generated by the device is very small even when compared to a light bulb.

Sources

Federal Trade Commission. News Release, 2001 [http://www.ftc.gov/opa/2001/05/fyi0128.htm]

See also

*Bug zapper