Fighting Pests With Sound Waves, Not Pesticides

Researchers invent a device that uses acoustics to mimic the mating call of an insect devastating Florida’s orange groves.

Guy Davies, an inspector for Florida's Division of Plant Industry, checks an orange tree for the Asian citrus psyllid, which carries the bacterium-causing 'citrus greening' disease. (Photo: Joe Raedle/Getty Images)

Nov 4, 2015· 1 MIN READ
Katharine Gammon has written for Nature, Wired, Discover, and Popular Science. A new mom, she lives in Santa Monica.

A tiny bug is threatening your morning orange juice.

In Florida, the Asian citrus psyllid, an aphid-size creature that feeds on the stems and leaves of citrus trees, cost the juice business $3.6 billion between 2006 and 2012. The real damage from “citrus greening” comes from bacteria spread by the bug, which causes leaves to turn yellow and kills the tree in a few years.

Researchers are looking into new ways to combat the pests, and one project focuses on sound rather than pesticides to disrupt the insects’ mating habits.

“We’re trying hard to cut down on use of pesticides in orange groves, partly because we are worried they’ll build up resistance to pesticides, and that will make things even worse,” said Richard Mankin, a research entomologist with the U.S. Department of Agriculture. He presented findings on acoustic disruption at the meeting of the American Acoustical Society this week in Jacksonville.

When a male psyllid wants to mate, he alerts a female by sitting on a leaf and buzzing his wings to send vibrations along leaves and branches. To disrupt that activity, the researchers created a device containing a piezoelectric buzzer and a microphone wired to a microcontroller.

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The device detects the incoming male call and emits a fake female response call through the buzzer before any neighboring psyllids can answer. When the male bug comes near the device, he gets snagged and immobilized on an adhesive surface. In lab tests, the insects subjected to the noise were four times less likely to find a mate than other psyllids.

Mankin said the gadget will be tested soon in orange groves. He has worked on similar sound disruptors for grapevines. It is unknown if the vibrational sound would have other ecological impacts.

The team is working to lower the price of the device, which costs between $50 and $200 and only covers two feet of a tree. Mankin said that in the short term, sound will not trump pesticides in fighting the Asian citrus psyllid. “Looking ahead, we’re expecting, however, that the psyllids will become resistant to the pesticides and that the costs of the new technology will continue to decrease,” he said.

Mankin said he hopes the device can work in tandem with pesticides, targeting infestations to reduce the amount of chemicals used and to help postpone the psyllids’ development of resistance to insecticides.

“We’re looking at the devices more as partners than as a replacement,” he said.

The idea of using sound to catch or deter insects has wider applications, Mankin noted. Acoustic devices have been successfully used to trap pests such as mosquitoes, midges, mole crickets, field crickets, moths, cockroaches, and fruit flies. Ultrasonic signals that simulate bat cries could deter night-flying insects.

“Trying to develop electronic-based pest control is a good idea, because it will help the production of food—and we need all the help we can get to feed the world’s growing population in the future,” Mankin said.