Evaluation of the impact of Hymenoscyphus fraxineus in ash stands in Serbia

The ash dieback was for the first time reported in Serbia on  Fraxinus excelsior and F. angustifolia  in 2015. Since the first report, the pathogen spread to the eastern and south – eastern parts of Serbia towards borders with Bulgaria, Romania and FYR of Macedonia. The aim of the study was to evaluate the impact of the disease on the health condition of ash trees and regeneration in stands and plantations in Serbia. The field studies were carried out over the whole country of Serbia. Distribution maps of European ash ( Fraxinus excelsior ) and narrow – leaved ash ( F. angustifolia) were made of the data obtained from the National Forest Inventory (2004 – 2006). Twenty – five publicly owned forest sites in which  Fraxinus species occurs were selected in Serbia. The selection of studied sites was non – random; the aim was to select representative ash forest types in different regions of the state. Different symptoms of the disease are present on leaves, branches and stem, but basal cankers have not been observed on the stems of ash trees so far. The disease is present both on young and adult trees, but the damages are more serious on younger trees because of apical shoot loss and deformation of the stems. The regeneration process in all ash stands is threatened by the pathogen. Observed defoliation on adult trees is in the range of 5 – 35% and the percentage of dead trees does not exceed 6% for all evaluated trees/stands. Monitoring of established study plots has shown that the annual progress of the disease, in young plantations, is at the level of 7 – 9% for the period of 2016 – 2018.