
Eavesdropping on Insects
in Soil and PlantsBy Jesús
García January 5, 2001Agricultural Research Service scientists
and colleagues have adapted acoustic techniques--commonly used by engineers to
predict mechanical failures--to detect insects hidden in soil and the interior
of plants. Researchers at ARS laboratories in Gainesville and Ft. Pierce, Fla., and
Corvallis, Ore., and colleagues at Auburn
University, University of Florida and
Montana State University have
collaborated on the development of an acoustic technique that uses sensitive
instruments like accelerometers, soil-probe electret microphones and
piezoelectric disks to pinpoint insect locations. These sensors convert
vibrations into electrical signals. Because insect pests often reside within plant structures and in soil, they
can be hard to detect. As a result, field searches often include a visual
inspection followed by digging, removal of the root mass or flushing with
water, all of which are damaging to the plant. So researchers have been trying
to find a less destructive way of determining the incidence of insect
infestations. The scientists conducted tests using a variety of insects and soil
conditions in Florida, Oregon and Puerto Rico. The kinds of insects used--like
the wheat stem sawfly and weevils that attack the roots of orange trees and
ornamental plants--were chosen for their economic importance and variations in
size. The portable acoustic sensors were found to detect insects within 180
seconds over distances of 10-30 cm, depending on the composition of the soil
and peak frequencies of the sound pulses. Those sound pulses were then averaged
to create profiles for each insect. Since background noises such as wind, airplanes and motor vehicles often
interfere with researchers ability to accurately determine the presence
of an insect, acoustic profiles were developed for them as well. Those profiles
were then used to conduct tests that compared acoustically predicted
infestations with insects found in the soil at recording sites. Under
laboratory or ideal field conditions--with low levels of low-frequency
background noise--insects within 30 cm were detected 100 percent of the time.
Under adverse conditions in the field, the technique was 75 percent reliable. This inexpensive and nondestructive pest-monitoring method may prove useful
to growers intent on using integrated pest management systems to lessen the
impact of a variety of insect pests on farm productivity. ARS is the
U.S. Department of Agricultures chief
scientific research agency. Scientific contact: Richard W. Mankin, ARS
Center for Medical, Agricultural, and
Veterinary Entomology, Gainesville, Fla., phone (352) 374-5774, fax (352)
374-5781, [email protected].
U.S. Department of Agriculture |