Dutch Elm Disease, caused by Ceratocystis ulmi USDA Forest Service Forest Health Protection, Southern Region Dutch Elm Disease, caused by Ceratocystis ulmi Importance. The greatest economic loss results from death of high value urban trees. Identifying the Fungus. In the laboratory the fungus readily produces easily identified, spore bearing structures. Identifying the Injury.
Symptoms normally progress rapidly through the crown.
Complete wilting often occurs within six weeks of infection. Generally, death of the infected tree is rapid. However, some asymptomatic trees have been found that had been infected for several growing seasons. The specific manner in which the fungus kills trees is unknown. The vascular system of the infected tree is affected, reducing the conduction of water and nutrients.