Ganodermacomprises a common bracket fungal genus that causes basal stem rot in deciduous and coniferoustrees and palms, thus having a large economic impact on forestry production.We estimated pathogen abundanceusing long-term, daily spore concentration data collected infive biogeographic regions in Europe and SW Asia.We hypothesized that pathogen abundance in the air depends on the density of potential hosts (trees) in the sur-rounding area, and that its spores originate locally. We tested this hypothesis by (1) calculating tree cover den-sity, (2) assessing the impact of local meteorological variables on spore concentration, (3) computing backtrajectories, (4) developing random forest models predicting daily spore concentration. The area covered bytrees was calculated based on Tree Density Datasets within a 30 km radius from sampling sites. Variations in daily and seasonal spore concentrations were cross-examined between sites using a selection of statistical toolsincluding HYSPLIT and random forest models.Our results showed that spore concentrations were higher in Northern and Central Europe than in South Europeand SW Asia. High and unusually high spore concentrations (> 90th and > 98th percentile, respectively) werepartially associated with long distance transported spores: at least 33% ofGanodermaspores recorded in Madeiraduring days with high concentrations originated from the Iberian Peninsula located >900 km away. Random for-est models developed on local meteorological data performed better in sites where the contribution of long dis-tance transported spores was lower. We found that high concentrations were recorded in sites with low hostdensity (Leicester, Worcester), and low concentrations in Kastamonu with high host density. This suggeststhat south European and SW Asian forests may be less severely affected byGanoderma. This study highlightsthe effectiveness of monitoring airborneGanodermaspore concentrations as a tool for assessing localGanodermapathogen infection levels.