The early symptoms of the disease appear from the latter half of June to the middle of July, when the leaves on one or more branches may wilt, droop and
curl. The leaves then turn brown and usually remain on the tree.
If the tree is infected later in the summer, the leaves will droop, turn yellow (this is called flagging) and drop prematurely. Late season infections are easily confused with normal seasonal changes.
All of these symptoms are accompanied by brown staining in the sapwood that can be seen by removing the bark of infected twigs.
Since other diseases can cause symptoms similar to those of DED, positive identification requires a laboratory test.
Signs of Beetle Activity
Beetle emergence holes, the size of the diameter of a pencil lead, and/or sawdust on the bark, indicate burrowing beetles. The beetles are 3.5 mm (1/8 inch) long. The characteristic pattern of the breeding galleries on the surface of the wood under the bark can also be used to identify the two elm bark beetle species.
The City of Edmonton is working with the Society to Prevent Dutch Elm Disease (STOPDED) and the Province of Alberta to prevent the spread of Dutch elm disease into our province. Because early detection is vital to controlling the spread of the disease, surveillance is top priority. That is why the City conducted an inventory of elms on private property and updated the public property elm inventory. Elm bark beetle traps are monitored throughout the city from May to September particularly in areas that receive out of province visitors and areas where elms are predominant.
Control of DED
Control of Dutch Elm Disease is currently limited to preventing its spread. There is no effective cure. In municipalities, such as Winnipeg or Regina, where the disease occurs, a multi-faceted program involving insect and disease surveillance, sanitation, insect control, tree maintenance, and planting alternate tree species are employed to manage the disease. Maintaining healthy elms and providing thorough sanitation has been a recommended strategy for many years and most management programs focus their resources in these areas. It is important to remove all diseased, dead, and dying elm trees. Whatever the reason for their poor condition, these trees are ideal breeding sites for bark beetles.
Prune Elms During October 1 to March 31
Prevention of Dutch Elm Disease starts by keeping elm trees healthy. Prune all dead wood that provides beetle habitat. Pruning of healthy elms, however, should only be done during the winter season when the beetles are not active (October 1 – March 31) as stipulated in Edmonton’s Dutch elm disease bylaw (pdf), since fresh tree wounds attract beetles.
Elms that suffer major injury, such as a lightning strike or storm damage during the summer, may be pruned, but branches must be chipped, burned or buried promptly. Written permission must be obtained prior to any emergency elm pruning performed during the elm pruning ban. Contact City of Edmonton 311 at (780) 442-5311.
Elm branches and logs must be disposed of properly. Bundle small branches, one inch or less in diameter, and place at the curbside with regular household waste.
Take large branches and logs (up to four feet) to special elm disposal bins at one of the following free elmwood recycling sites:
For citizens who need help with pruning, the City recommends using professional arborists certified by the International Society of Arboriculture.
Remember, Edmonton’s Dutch elm disease bylaw introduced in 1997 prohibits the storage of any elmwood that you may have pruned. Help us keep Edmonton’s elm trees DED free.
Information from www.edmonton.ca