Abstract

Dieback of Fraxinus excelsior and Fraxinus angustifolia, caused by Hymenoscyphus pseudoalbidus (anamorph Chalara fraxinea), is presently the most important damaging factor of hardwood trees in Austria. Results from permanent monitoring plots in Lower Austria show that disease development on mature ash trees was slow from 2008 to 2010. In 2008, mean dieback intensity ranged from 1 to 34% on the 14 plots (mean 11 %). In 2010, mean dieback intensity per plot varied between 2 and 38% (mean 16%). Only on three of the 14 monitoring plots one out of the 20 sample trees had died during the observation period. Disease intensity was higher on most plots in the western parts of Lower Austria than on most plots in the eastern parts of the province. Relations between disease intensity and site and stand factors are discussed.

Key words: Hymenoscyphus pseudoalbidus, Chalara fraxinea, ash dieback, emerging forest disease, disease monitoring.