Dutch Elm Disease
Dutch Elm Disease is an extremely threatening vascular infection which attacks and kills xylem cells in elm trees.
Threat to Trees
In highly susceptible trees, mortality could occur within a year, others will last for several years. The average time in which a community loses half of its elms is between 7 and 30 years.
Overwintering pathogens in dying or recently dead elms are transported by their vectors, European bark beetles and the native elm bark beetle. Pupating larvae leave dead logs carrying the disease and deposit fungal spores in healthy elms which block and kill xylem cells. Root grafts can also aid in the infection of other trees.
Signs & Symptoms
Yellowing and wilting of leaves on individual branches is the first symptom
of disease. As branches die, leaves curl up as the branches die and leaves may eventually fall. If bark is peeled back, some brown discoloration may be visible on the outer layer of the wood, and this will usually occur before the foliage is affected. Xylem browning occurs in a ring or circle of brown dots.
Ophiostoma grow and reproduce exclusively within elm trees, acting either as parasites or saprophytes consuming dead elm tissue.
North America, 1928