Host Tree

The disease affects species in the genera Ulmus and Zelkova.

European elms: Ulmus glabra Huds., U. minor Mill. U. laevis Pallas

Among European species, there is the unique example of the European white elm U. laevis, which has little innate resistance to DED, but is eschewed by the vector bark beetles and only rarely becomes infected. Recent research has indicated it is the presence of certain organic compounds, such as triterpenes and sterols, which serves to make the tree bark unattractive to the beetle species that spread the disease (Newhouse 2007). Another reason maybe the narrower vessels, that makes the species less vulnerable (Venturas et al. (2013). Recent research in Sweden has established that early-flushing clones are less susceptible to DED owing to an asynchrony between DED susceptibility and infection (Ghelardini 2007).

There is a wide range of elm hybrid varieties, usually crossed with Asian elms (Martín et al. 2014), some of them are generally resistant to DED (Eisele 2018) and are recommended to be planted in green areas.

It is important to know that that in Northern Europe elms grow in the northern limit of their natural range (Laasimer 1965, Ignatieva et al. 2011) resulting in an increase in their sensitivity to climate change and in their susceptibility to pathogens (Hanso and Drenkhan 2007, 2013).