Pesky biting insects can force even the most ambitious gardeners back indoors. By appealing to consumers' appetite for environmentally friendly, nonchemical products, manufacturers advertise ultrasonic devices as a safe way to keep bugs away while working outdoors. Sound frequency devices, however, do not repel insects. Unfortunately, good marketing strategies often trump sound science when it comes to repelling insects.
Manufacturers promote their ultrasonic devices by claiming the machines protect people from insect-borne diseases such as West Nile virus that lurk in gardens and other outdoor spaces. Taking advantage of many humans' aversion to chemicals, they market their products as a better alternative than insect repellent chemicals, including DEET. Based on the principle that insects locate mates or avoid predatory insects by the sound of beating wings, the machines supposedly mimic the frequency of wing beats and cause biting insects to avoid the location of the sound.
Various scientific studies have proven that ultrasonic insect repellent devices do not repel insects. From as early as 1985, the U.S. Federal Trade Commission has issued warnings to and brought legal action against manufacturers and sellers of the devices, indicating that advertising claims must be supported by scientific evidence. Staying well covered, removing nearby standing water and using a repellent containing DEET are the best ways to avoid insect bites when working in your garden.