ACOUSTIC DETECTION AND MONITORING OF Cephus cinctus SAWFLY LARVAE IN WHEAT STEMS.

R. W. Mankin¹ & D. K. Weaver².

¹USDA-ARS-CMAVE, P. O. Box 14565, Gainesville, FL 32604, USA, E-mail rmankin@gainesville.usda.ufl.edu; ²Dept. of Entomology, Montana State Univ., P.O. Box 173020, Bozeman, MT 59717-3020, USA.

The behavior of Cephus cinctus Norton larvae in wheat is difficult to study because they are hidden from view inside the stems. We tested the feasibility of using acoustic techniques to nondestructively identify infested stems and monitor larval activity. Adult females were allowed to oviposit in small pots of wheat. After three weeks, a small accelerometer was clamped to the base of each stem and sounds were recorded for ~3 minutes. Infested stems and uninfested stems in motion produced short clicks ~0.5 msec in duration. The clicks could be detected in the moderate background noise of a research laboratory without using an insulated room or anechoic chamber. No clicks were recorded from stationary, uninfested stems. After recording, the stems were cut and the locations and weights of any larvae were noted. The signals were analyzed using custom-written digital signal processing software. Methods were developed to distinguish larval movement and feeding activity from background noises. In the initial study, we identified putative larval sounds from 17 of the stems tested. All were infested with larvae (mean weight = 5.25 +/- 0.77 mg). The mean rate of clicks produced by larvae in the infested stems was 1.41 +/- 0.26 clicks per minute. Our experience in the initial study led to development of an improved device for clamping the accelerometer to the wheat stem. The use of nondestructive techniques will enable the future monitoring of long-term activity patterns.

Index terms: sound, behavior, activity pattern.

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10/21/08 Richard Mankin