Signs and Symptoms

DED is a lethal vascular wilt, being tracheomycosis-type disease (Brasier 2001), that reproduces by budding, similar to yeast-like fungi and the spores spread rapidly in xylem with sap flow (Webber and Brasier 1984). In response to the fungal infection tyloses and resins are accumulated in xylem vessels that eventually block water transportation to the crown causing the tree to wilt and finally death (Sherif et al. 2014).

The first symptoms of which are yellowing and browning (flagging) of leaves, a cross-section of an elm twig showing brown spots or streaks in the recent wood rings (Clinton and McCormick 1936; Stipes and Campana 1981). 

Flagging leaves of dying elm