Diagnosing emerging infectious diseases of trees using ground penetrating radar

Ash dieback, acute oak decline (AOD) and Xylella Fastidiosa are Emerging Infectious Diseases (EIDs) that have spread rapidly in European forests during the last decade. Quarantine measurements have mostly failed to repress the outbreaks and millions of trees have already been infected. Identifying infected trees in a non-destructive manner is of high importance for monitoring, managing and preventing EIDs. The aim of this paper is to examine the capabilities of Ground Penetrating Radar (GPR) on evaluating the internal structure of tree-trunks and detecting tree-decay associated with EIDs. Traditionally used processing schemes tuned for GPR line-acquisitions are modified accordingly to be compatible with the new measurement configurations. In particular, a detection framework is presented based on a modified Kirchhoff and a reverse-time migration. Both of the aforementioned methodologies are compatible with measurements taken along closed irregular curves assuming a homogeneous permittivity distribution. To that extent, prior to migration, a novel focal criterion is used that estimates the bulk permittivity of the host medium from the measured B-Scans. The suggested detection scheme is successfully tested on both numerical and laboratory measurements, indicating that GPR has the potential to become a coherent and practical tool for detecting tree-decay associated with EIDs.