Perspective and Promise: a Century of Insect Acoustic Detection and Monitoring

Acoustic devices provide nondestructive, remote, automated detection, and monitoring of hidden insect infestations for pest managers, regulators, and researchers. In recent decades, acoustic devices of various kinds have been marketed for field use, and instrumented sample containers in sound-insulated chambers have been developed for commodity inspection. The efficacy of acoustic devices in detecting cryptic insects, estimating population density, and mapping distributions depends on many factors, including the sensor type and frequency range, the substrate structure, the interface between sensor and substrate, the assessment duration, the size and behavior of the insect, and the distance between the insects and the sensors. Considerable success has been achieved in detecting grain and wood insect pests. Microphones are useful sensors for airborne signals, but vibration sensors interface better with signals produced in solid substrates, such as soil, grain, or fibrous plant structures. Ultrasonic sensors are particularly effective for detecting wood-boring pests because background noise is negligible at > 20 kHz frequencies, and ultrasonic signals attenuate much less rapidly in wood than in air; grain, or soil. Problems in distinguishing sounds produced by target species from other sounds have hindered usage of acoustic devices, but new devices and signal processing methods have greatly increased the reliability of detection. One new method considers spectral and temporal pattern features that prominently appear in insect sounds but not in background noise, and vice versa. As reliability and ease of use increase and costs decrease, acoustic devices have considerable future promise as cryptic insect detection and monitoring tools.