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Listening to Larvae


  Entomologist Richard W. Mankin has eavesdropping down to an art. Using a self-developed computer program that can tell the difference between the sounds made by termites, root weevils, and many other insects, he's found a way to expose hidden insects that infest and damage packaged goods, ornamentals, and other valuable agricultural commodities, even golf courses.


"Typically," says Mankin, "the only way to determine whether there is an infestation of insect larvae is to wait for adults to emerge or to dig or cut out a sample. By that time, it can be too late. It's also not economical to dig up large parts of a field or crop to check for infestations."


Mankin, who is with the ARS Center for Medical, Agricultural, and Veterinary Entomology's Post-Harvest and Bioregulation Research Unit in Gainesville, Florida, has developed a nonintrusive eavesdropping tool using a sensor that measures vibrations given off by insects as they move and feed.


The sensor can be attached to a spike that is pushed into soil or poked into a tree trunk, or it can be clamped to a plant stem. By poking the specially rigged nail into a tree or a plank, Mankin can tell whether it's infested with termites just from the sounds he hears. A series of scrapes and clicks in particular rhythms at particular frequencies reveal insects "on the take." Mankin can also use the specially designed clamps to eavesdrop on larvae in stored products or sawflies inside wheat stems.


Different insects give off different sounds, depending on their feeding and movement patterns, their sizes, and what they are eating. Mankin has developed a computer program to distinguish larval movement and feeding activity from background noises, like wind or blowing leaves, and in many cases, the program can distinguish different insects from each other. This is done partly by matching new sounds with previously recorded sounds.


"Our long-term goal is to develop rapid, nondestructive techniques for pinpointing hidden infestations, which should reduce pesticide use and decrease treatment costs," Mankin says. —By Tara Weaver-Missick, Agricultural Research Service Information Staff.


Richard W. Mankin is at the USDA-ARS Center for Medical, Agricultural, and Veterinary Entomology, Postharvest and Bioregulation Research Unit, 1700 S.W. 23rd Dr., Gainesville, FL 32608; phone (352) 374-5774, fax (352) 374-5781.

"Listening to Larvae" was published in the March 2001 issue of Agricultural Research magazine.

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