Detection of<i>Ganoderma australe</i>Decay in Three<i>Acacia confusa</i>Trees: A Case Study

Abstract Background This study aims to utilize various nondestructive methods to assess the internal trunks of 3 Acacia confusa trees affected by Ganoderma australe decay. Methods Visual Tree Assessment (VTA) was employed to examine the trees, selecting 3 Taiwan acacia ( Acacia confusa ) trees at the base of which G. australe fungal fruiting bodies were growing, identified as severely damaged and classified as having an immediate hazard level. Subsequently, a stress wave device was used to detect the cross-sectional area of these trees at the locations where G. australe fungus was growing in order to obtain 2D tomographies of stress wave velocity. Following this, a resistance drilling instrument was used to examine the same cross-sectional areas, acquiring resistance drilling amplitude data. Finally, the 3 trees were felled, and 15-cm thick discs were cut from the same cross-sectional areas for laboratory testing. Results Using 2D sonic tomography and a corresponding velocity grid map of stress wave velocity revealed areas with varying velocities across the trunk cross sections. Drill resistance profile curves depicted changes in resistance strength, while visual inspections of disk cross sections indicated the location and severity of decay. Additionally, pilodyn penetration testing showed different penetration depths on the surfaces of the disk cross sections. Conclusion The study discusses the use of these detective methods to discover the location and extent of decay within tree trunks and assesses the percentage of decay in cross-sectional areas, providing a reference for tree risk assessment levels.