Noncontact ultrasound detection of exotic insects in wood packing materials

Nondestructive methods for detection of wood-boring insects such as the Asian longhorned beetle (ALB), Anoplophora glabripennis (Coleoptera: Cerambycidae) inside solid wood packing materials is a valuable tool in the fight to exclude exotic insects from attacking a nation's timber resources. Nondestructive, non-contact, ultrasound was investigated as a potential method for detection of cerambycid larvae in solid wood packing materials. If successful, this technology could be used by port inspectors attempting to detect and eliminate the unintentional importation of exotic pests in commercial trade shipping materials. One-inch-thick samples of aspen (Populus spp.) and red pine (Pinus resinosa) wood with and without cerambycid larvae in holes were scanned with 200-kHz ultrasound waves above wood fiber saturation and at low moisture conditions. A pair of noncontact transducers acting as the emitter and the receiver was placed on either side of the wood sample. The resulting transmission data were used to produce ultrasonic images with a state-of-the-art, signal analyzer system for nondestructive sensing applications. We successfully generated detailed c-scan images for all wood samples, regardless of species and wood moisture condition. Artificially drilled holes in the wood samples could also be clearly identified in the c-scans. Although both the larva and its movement could be detected in the images when placed on top of the wood, neither was detectable when placed inside the sample. We concluded that with the current technology, 200-kHz ultra-sound imaging is not a feasible method for detecting insects in wood packing material. Future research focusing on other forest product or entomology applications such as density measurements of plywood, grading of lumber, and measurement of larval feeding rates derived from changes in tunnel characteristics should be undertaken as these applications may prove feasible with the current state of this technology.