Chalara fraxinea

(Hymenoscyphus pseudoalbidus) (Ash dieback) is the highly fungal invasive species on woody plants in Europe, probably of Asian origin. Since first observation in the 90`s this disease has dramatically reduced Ashe trees in forest stands, river banks and in the countryside25. The effects of the disease have been dramatic. In Lithuania for example the disease caused a decrease of the ash forest area from 53,000 to 38,000 hectares between 2001 and 200926 and in Denmark no ash trees have been planted since the disease became established. The fast spread and the serious damage caused by the disease led to the EU-COST FRAXBACK actions, the NORNEX project (focusing on genomics of the pathogen and on elucidating the genomic background of resistance in surviving ash trees) and other National initiatives testing limited sets of ash tree selections. In synergy with these initiatives, EMPHASIS will bring together all important selections of nursery trees for urban use throughout the EU and test for resistance against Chalara fraxinea. This will be extended for seedlings from selected seed sources from other projects and initiatives mentioned above. Trees will be sampled from test plots in two different countries and tested for resistance. Building on the above mentioned preliminary results and through a close co-operation with the tree nursery sector it will be possible, within the timeframe of the project to provide guidelines for managers of urban green areas which species and cultivars can be used to prevent future losses due to ash dieback disease and to maintain the important role of Fraxinus species and cultivars in the urban infrastructure.

Management approach

For Host plant resistance: applying new resistance sources.

Solution proposed by EMPHASIS

For Host plant resistance: Report on ash tree varieties less susceptible or resistant to Chalara fraxinea and their ability to practice (PU) for selection of resistant cultivars

Contact person/organisation

Jelle Hiemstra (WUR)