Spatiotemporal dynamics of termite infestation in urban Araucaria cunninghamii: A case study in Taipei

Termite feeding on the trunk cross-sections of Araucaria cunninghamii in Taipei, Taiwan, was examined using 2D stress wave imaging (FAKOPP system). Six inspections were conducted at 2-month intervals to monitor six trees. 2D cross-sectional stress wave velocity images were created at different heights (30–180 cm) to assess termite feeding damage. Termite damage, quantified as damage ratio (DR, %), ranged from 0% to 55% across different trees and heights, with maximum increases of up to 21% in DR observed over a 2-month period. In the investigated cases, termites primarily fed on the interior of tree trunks. The feeding pattern typically extended longitudinally, then proceeded in a tangential (circular) direction, and finally moved radially. This study identified Coptotermes formosanus as a key termite species involved. Typically, termites prioritized feeding on the earlywood over the latewood. The periods with the highest damage to trunk cross-sections due to termite feeding occurred during seasons with higher temperatures and relative humidity. Damage initially appeared near the heartwood or the boundary between the heartwood and sapwood, gradually expanding into the heartwood. Of the six trees monitored for the full study duration (after one tree was felled for validation), subterranean termite tunneling was observed as the primary pattern in three trees, while aerial swarm invasion patterns were inferred for two trees based on initial damage locations.