Submitted to: Journal of Agricultural and Urban Entomology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/1/2004
Publication Date: 10/10/2005
Citation: Mankin, R.W., Weaver, D.K., Grieshop, M., Larson, B. 2005. Acoustic system for insect detection in plant stems: comparisons of Cephus cinctus in wheat and Metamasius callizona in bromeliads. Journal of Agricultural and Urban Entomology. 21(4):239-248. Interpretive Summary: USDA, ARS, scientists at the Center for Medical, Agricultural, and Veterinary Entomology in Gainesville, FL, Montana State University, and the University of Florida have cooperated in testing the efficacy of portable acoustic technology to detect hidden infestations of insects in plant tissue. The wheat stem sawfly is a pest of wheat in the Northern Plains and M. callizona is a recently introduced pest of ornamental bromeliads in Florida. Both are difficult to detect and control because they feed inside the stem or the core of their host plants, hidden from view. The research demonstrated that these insect species can be detected easily by acoustic techniques. The use of acoustic detection and analysis reduces the amount of time and labor associated with the detection and sampling of these insects and can lead to cost-reductions in integrated pest management programs.
Technical Abstract: Cephus cinctus Norton larvae feed and pupate inside wheat stems, hidden from predation or behavioral observation. We have developed and tested nondestructive acoustic techniques to identify infested stems and monitor larval activity. A clamping system was devised to attach an accelerometer to the base of a wheat stem without damaging it. Larvae feeding and moving inside the stems produced brief, high-frequency ticks loud enough to be detected in moderate background noise without using an insulated room or anechoic chamber. The larval sounds were recorded and analyzed using author-written digital signal processing software that distinguished larval movement and feeding activity from background noises. Experience with the system led to development of an improved device for clamping the accelerometer to the wheat stem. The improved system was used in a comparative study to detect Metamasius callizona (Chevrolat) larvae hidden inside meristemmatic tissue of Tillandsia utriculata (L.), an ornamental bromeliad. Temporal and frequency patterns of sound pulses generated by the two species were compared in relation to insect size and differences in the structural properties of the substrate. Both insects could be detected without difficulty because their sounds had significant high-frequency components. As expected, the larger (300-400 mg) M. callizona generated louder sounds than the (3-8 mg) C. cinctus. The improved accelerometer/clamp system can be a useful tool for monitoring the movement and feeding activity of C. cinctus and other insects that are difficult to view inside plant tissue.