THz tomography for detecting damages on wood caused by insects

Annually, wood-destroying insects cause severe damage in forests. The widespread population of typographer (Ips typographus), a beetle species from the subfamily of bark beetles (Scolytidae) in Europe, mainly occurs in coniferous wood, especially in spruce (Picea abies), the most silviculturally relevant wood species. The typographer infestation is detected mainly by visual monitoring and without invasive techniques only recognizable at a late stage. Terahertz radiation has shown enormous potential in nondestructive testing. THz measurements in the time-domain performed with a robotic THz system can be used for 3D reconstruction of the internal structure of the samples. In this article, we report the detection of a change in the wood structure of spruce caused by typographer burrows.