American elm trees are fast growing, graceful and long living. They are also tolerant of poor growing condition and poor air quality. Because of this, they were once considered an ideal street tree. In the past, you could drive down residential neighborhood and see rows of large, beautiful elm trees lining the streets. That is no longer the case in many American cities due to Dutch Elm Disease, one of the most devastating plant pathogens in the US and Europe. This disease has killed millions of elm trees despite all efforts to control it.
Dutch elm disease is spread from infected treed to healthy trees by fungal spores which are carried on the backs of bark beetles. Beetles overwinter in diseased trees and move to healthy trees to feed in spring and summer. The disease is also spread through root grafts, which form between trees growing in close proximity. There are an estimated 3,500 elm throughout Portland. Approximately 1,500 elm trees have already been killed since the late 70’s due to this disease.
On June 10, 1987, the Portland City Council passed an ordinance to try to control this destructive disease by requiring infected elms trees to be suitably removed. Contaminated wood and debris must be properly disposed of and stumps and roots must be ground to prevent the disease from spreading through the root graphs. In an effort to preserve healthy elm trees, most tree pruning activities may ONLY be preformed from October 16th-April 14th annually when bark beetles are less active. Tools used to prune elm trees must be sanitized before and after to prevent potential spread of this disease.
While there is no cure for infected elms, some preventative measures are available. Call us today to scheduled a no-cost consultation to assess the health and needs of your elm (or other) trees. Spring pruning deadline is 4/14. Call today!