Tomodensitometry as a tool to detect and study xylophagous insects

Exotic insect species are increasingly problematic with the rise in international trade. Detecting and removing these insects is crucial for imported and exported goods, including wood products. The transportation of wood significantly contributes to the spread of the Emerald Ash Borer, Agrilus planipennis (Coleoptera: Buprestidae). This Asian species causes high mortality in ash trees in its introduced range due to the trees' weak defenses and lack of natural predators. Similarly, there are concerns in Europe about the potential introduction of the Bronze Birch Borer, A. anxius, native to North America, which could lead to significant birch tree mortality. Effective detection methods and phytosanitary measures are essential to prevent their introduction. This study assessed tomodensitometry, or CT-scan, as a detection method for these two Agrilus species, using debarking as the reference method. We also compared AI detection on CT-scan images to human detection. The CT-scan allowed us to accurately measure insect depth within ash and birch trees, aiding in recommending appropriate phytosanitary measures for wood product trade. Both techniques effectively detected insects in ash, paper birch, and yellow birch. However, the number of A. anxius detected varied with the technique used and the sample diameter. Insect depth also varied by tree species, sample diameter, and life stage. While CT-scan is more costly and requires specialized equipment, debarking is more time-consuming, especially when counting insects.