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. Since these devices are not regulated under the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA) in the United States, the US EPA does not require the same kind of efficacy testing that it does for chemical pesticides.
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Types of devices
There are two types of electronic pest control devices widely available: electromagnetic and ultrasonic.
Electromagnetic
Electromagnetic ("EM") pest repelling devices claim to affect the nervous system of ants, mice, spiders, and other rodents. There have been similar studies on effects of EM radiation emitted by cellphones on humans.
Ultrasonic
Ultrasonic devices operate through emitting short wavelength, high frequency sound waves that are too high in pitch to be heard by the human ear (generally accepted to be frequencies greater than 20,000 Hz). Humans are usually unable to hear sounds higher than 20 kHz due to physiological limitations of the cochlea, though there is considerable variation between individuals, especially at such high frequencies. Some animals, such as bats, dogs, 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 lacewings and moths can detect ultrasound as high as 240,000 Hz produced by insect-hunting bats. Contrary to popular belief, birds cannot hear ultrasonic sound. Some smartphone applications attempt to use this technology to produce high frequency sounds to repel mosquitoes and other insects, but the claims of effectiveness of these application and of ultrasonic control of mosquitoes in general has been questioned. The ultrasonic repeller has several inconvenient side effects in addition to its questionable effectiveness
Insects detect sound by special hairs or sensilla located on the antennae (mosquitoes) or genitalia (cockroaches), or by more complicated tympanal organs (butterflies, grasshoppers, locusts, and moths).
Radio wave pest control
The concept of radio wave (RW) or radio frequency (RF) to control the behavior of living organisms has shown promise. According to Drs. Juming Tang and Shaojin Wang at Washington State University (WSU) with colleagues at the University of California-Davis and USDA's Agricultural Research Service in Parlier, California, since RF energy generates heat through agitation of bound water molecules, it generates heat through ionic conduction and agitation of free water molecules in insects. As a result, more thermal energy is converted in insects.
RF treatments control insect pests without negatively affecting food stuffs and storage locations. RF treatments may serve as a non-chemical alternative to chemical fumigants for post-harvest pest control in commodities (such as almonds, pecans, pistachios, lentils, peas, and soybeans), reducing the long-term impact on the environment, human health, and competitiveness of agricultural industries.
Studies
"Ultrasound and Arthropod Pest Control" (2001), an extensive Kansas State University study, confirmed that ultrasonic sound devices do have both a repellent effect as well as reduces mating and reproduction of insects. However, the results were mixed, and ultrasonic sound had little or no effect on some pests. Ultrasonic devices were highly effective on crickets, while the same devices had little repellent effect on cockroaches. Additionally, the results were mixed: some devices were effective, while others had no effect depending on the test subject. The study also concluded there was no effect on ants or spiders in any of the tests. They concluded, based on the mixed results, that more research is needed to improve these devices.
A 2002 study sponsored by Genesis Laboratories, Inc. (the maker of the Pest-A-Cator/Riddex series of electronic repellent devices) does lend some credence to the ability of electronic repellent devices to repel certain pests in controlled environments. “Preliminary study of white-footed mice behavior in the test apparatus demonstrated a significant preference for the non-activated chamber among both sexes.”
In 2003, the Federal Trade Commission required Global Instruments, the maker of the Pest-A-Cator/Riddex series of electromagnetic pest control devices, to discontinue any claims for their efficacy until they are backed by credible scientific evidence. This ban continues to be in effect.
In 2009, Victor Pest obtained positive results from independent researchers which resulted in two ultrasonic devices' being granted registration by the Canadian EPA (PMRA). The results from the tests were: the device “successfully repelled the rodents from the protected area in 13 of the 17 sites. This represents a 81.3% success rate...the average number of days before rodent activity was stopped was six days".
Effects on cockroaches
Cockroaches respond to electronic pest control devices by moving about a bit more than usual, but don't appear eager to escape from the sound waves. This includes devices that emit a uniform frequency as well as those that emit changing frequencies of ultrasound. Researchers were able to use the increased cockroach activity to good effect by increasing the rate at which they caught the roaches in sticky traps.
Effects on mosquitoes
Effects on rodents
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 for a few minutes to a few days, but they will nearly always return and resume normal activities. Other tests have shown that the degree of repellance depends on the frequency, intensity, and pre-existing condition of the rodent infestation. The intensity of such sounds must be so great that damage to humans or domestic animals would also be likely; commercial ultrasonic pest control devices do not produce sounds of such intensity.
Safety
Professor Tim Leighton at the Institute of Sound and Vibration Research], University of Southampton, U.K. produced an 83-page paper entitled "What is Ultrasound?" (2007), in which he expressed concern about the growth in commercial products which exploit the discomforting effects of in-air ultrasound (to pests for whom it is within their audible frequency range, or to humans for whom it is not, but who can experience unpleasant subjective effects and, potentially, shifts in the hearing threshold). Leighton claims that commercial products are often advertised with cited levels which cannot be critically accepted due to lack of accepted measurement standards for ultrasound in air, and little understanding of the mechanism by which they may represent a hazard.
The UK's independent Advisory Group on Non-ionising Radiation (AGNIR) produced a 180-page report on the health effects of human exposure to ultrasound and infrasound in 2010. The UK Health Protection Agency (HPA) published their report, which recommended an exposure limit for the general public to airborne ultrasound sound pressure levels (SPL) of 70 dB (at 20 kHz), and 100 dB (at 25 kHz and above).