I don't think these devices are effective. In years past, the US Federal Trade Commission sued manufacturers of these devices because while they claim these devices repel insects, the manufacturers provide no evidence they work.
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After the lawsuit, the manufacturers just lay low for a while, then change the frequency of the device and start manufacturing them again. As long as people buy them, they will continue to manufacture these fraudulent devices.
Those of us working with the public wonder why there is so much fascination with sound devices as insect or wildlife repellents.
Insects don't really have "ears" like we have. What isn't easy to understand is why people believe these ultrasonic sound frequencies would be repellent to insects. My husband did cockroach research on some of these devices back in the '80s and found they didn't work, but negative data is hard to publish.
Some animals can hear ultrasounds but why would these high frequencies drive them away? This is based on the assumption that insects can be annoyed by sound in the same way that humans are. One claims to imitate the sound of the mosquito's predator, the dragonfly, but these are useless. In any case, the dragonfly's wing beat frequency of between 20 and 170Hz, which is not ultrasound.
My guess is that people want to believe there is an easier way, a sort of wishful thinking. It's the same idea that gets people to mix concoctions of herbs and spices in a bid to keep pests away.
I don't know of any entomologists that recommend these devices. It they did, the manufacturers would be giving grants to support research.
It is particularly troublesome that companies are cashing in on fraudulent mosquito repelling devices when readily available products (with active ingredients, DEET, picaridin, IR-3535) work pretty well. It is even more troubling to think that people might actually use one of these devices and contract a debilitating disease from a mosquito bite.
Martyn Robinson from the Australian Museum also commented, "Yes, we had some at work and tested them. The cockroaches laid eggs in them."
Response: Barb Ogg, extension educator, UNL, Nebraska
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