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. 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.

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.^[1]

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 (all frequencies greater than 20,000 Hz). Humans are unable to hear sounds higher than 20 kHz due to physiological limitations of the cochlea. Some animals, such as bats, dogs, and rodents, can hear well into the ultrasonic range.^[2] 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.^[3]

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, RF energy generates heat through agitation of bound water molecules, This process 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.

Effects on pests

Studies

"Ultrasound and Arthropod Pest Control" (2001), an extensive Kansas State University study,^[4] 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.^[4]

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.”^[5]

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.^[6][7] 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".^[8]

Effects

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

• A 2007 review article examined 10 field studies, in which ultrasonic repellent devices had been put to the test, and concluded they "have no effect on preventing mosquito bites" and "should not be recommended or used". It goes on: "Given these findings from 10 carefully conducted studies, it would not be worthwhile to conduct further research on EMRs [electronic mosquito repellents] in preventing mosquitoes biting or in trying to prevent the acquisition of malaria".^[9]
• Bart Knols, an entomologist who chairs the advisory board of the Dutch Malaria Foundation and edits the website Malaria World, claims there is "no scientific evidence whatsoever" that ultrasound repels mosquitoes.^[10]
• In 2005, the British consumer magazine Holiday reported the results of its test of a range of mosquito deterrents. The magazine's editor Lorna Cowan described the four appliances that used a buzzer as "a shocking waste of money" which "should be removed from sale". One, the Lovebug, a ladybird-shaped gadget designed to be clipped onto a baby's cot or child's pushchair - was singled out as a particular cause for concern, because of the likelihood that parents would trust it to keep mosquitoes away, and their children would be hurt as a result. (The Lovebug is still readily available in Europe, though it was withdrawn from the US market after the Federal Trade Commission reprimanded the manufacturer Prince Lionheart.)^[10]

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.^[11]

Safety

Professor Tim Leighton^[12] at the Institute of Sound and Vibration Research], University of Southampton, U.K.^[13] 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.^[14]

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.^[15] 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).^[16]

See also

• Bug zapper
• Fly-killing device
• Pest control

References

Further reading

• "News Release". Federal Trade Commission. 2001. 
• "Consent Agreement". Federal Trade Commission. July 2003. 
• "Press Release Radio Waves May Offer a New, Environmentally Safe Pest Control Method". USDA. 2008.