-- Do so called "pest repellers" work? --
Summary: Various devices on the market claim to repel bugs and/or rodents with ultrasonic or electronic (electro-magnetic) energy. These devices have, however, not been thoroughly tested and in fact have failed to do what they claim to do in the few scientific trials that have been done.
Electronic** pest control devices
Electronic pest control devices (so called "pest repellers") come in several types. Some claim to repel insects, spiders, and rodents by ultrasonic, or very high pitched, sound. Others claim to produce an electromagnetic field that is repellent while newer devices add ionic air cleaning. Typically the small devices are plugged directly into electric wall outlets or through an adapter cord.
The claim is that these devices "drive pests out" of a room, or structure, by a combination of electromagnetic, sonic and/or ultrasonic energy, the idea is that the high energy waves are repellent to the various pests -- everything from cockroaches to mice.
**These devices are sometimes called ultrasonic pest control or sonic pest control.
Do they really work?
Unfortunately, no. None of these devices have been scientifically shown to do what they claim they do. I would love to recommend these as a safe alternative to indoor pesticides if they worked -- but, I can't. And, in 2001 the FTC even warned manufactures and retailers that claims of efficacy must be backed by scientific data (see FTC Warns Manufacturers and Retailers of Ultrasonic Pest-control Devices).
The bottom line is that if manufacturers have scientific data that demonstrates that these devices work they should make it easily available, but of course they don't. Instead, testimonials are the only evidence of efficacy they offer. Testimonials, such as "I tried it and it worked great!", are simply not reliable because people see what they want to see. To be credible the claims must be backed up with proper scientific data.
Manufacturers have argued that there is no evidence that the devices don't work. This is true but only because you can't prove a negative result (see updates below). However it is the complete absence of published, scientific data that is most striking. I have not been able to find even one positive test result that has been published in a scientific journal.
I believe it is the responsibility of manufacturers to provide credible data that the devices they sell actually work. Otherwise, their unsupported claims are no better than "snake oil" in my opinion. Check their literature and you'll not find credible, published evidence of scientific testing. I'll make an offer, if published studies do exist and these studies confirm a claimed effect on pest behavior, I'll gladly amend this page and include the results. All the manufacturers need do is send me a reference or the name of a credible researcher that I can contact.
Since this page was originally posted a few studies have been conducted. However they did not generally support manufacturer's claims:
In 2002 a study was conducted at Kansas State University that tested a commercial ultrasonic device against reproduction in the Indian meal moth. The study found that moths enclosed in a chamber and subjected to high (94 dB) ultrasonic sound produced fewer sperm (in males), fewer larvae, and the larvae weighed less. While these results are interesting I don't think they tell us much about how the devices perform under real world situations. High levels of ultrasonic sound may act as a sort of birth control for moths, at least under these artificial conditions. Whether or not this would result in useful pest management remains to be tested.
In another article published in 2006 by the same researchers who conducted the 2002 at KSU they tested the ultrasonic devices for repellency against German cockroaches. In short, the devices failed to show any repellency and they concluded that the devices would not be useful for pest management of cockroaches. My guess is that these researchers got no more research funding from this industry!
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