| | The lab analysis of a sample taken from a dying elm tree in Wainwright on June 25, 1998 has confirmed that the Dutch elm disease (DED) fungus Ophiostoma nova-ulmi was the cause of its demise. This fungus is considered to be the most virulent among the DED fungi, and is thought to be responsible for the second pandemic of this disease across North America.
The tree was reported by a STOPDED employee while completing the elm inventory in Wainwright, 200 km south-east of Edmonton. The culture was inspected Authority Research Station, U.K. Professor Brasier was the one who first described the new virulent strain of DED, O. nova- ulmi.
DED is a deadly fungus that can affect any elm tree. The disease is primarily spread from one elm tree to another by two beetle vectors, the smaller European beetle (SEEBB) and the native elm bark beetle (NEBB). Since the introduction of the disease from Europe in 1930, it has destroyed millions of American elm trees across North America. DED is prevalent in Manitoba, Saskatchewan and Montana.
The infected tree was removed and burned at the Wainwright dump on July 28, 1998. The tree was treated as having DED although the results were not final at that time. For the remainder of the 1998 season, addition pheromone traps were placed throughout the municipality, but no beetles were found. It is still unknown which vector was present. All the remaining elm trees in the municipality were surveyed for DED and no other samples tested positive for DED. It is believed that firewood brought into the province from a DED infested area was the source of the infection.
In 1999, monitoring for the elm bark beetles, surveillance of the elm trees and the level of public awareness in Wainwright and the surrounding area were increased. All the elm trees and traps were inspected monthly. Again no DED vectors were found and no other elm trees showed any DED symptoms. The Town of Wainwright Parks Department removed a number of the dead elm trees which were identified in the elm inventory. Additional pruning of the dead wood in the healthy elms will be done between October 1,1999 - March 31, 2000.
The infected tree in Wainwright appears to be an isolated case of DED, as no other trees in the province have been found to have the disease. Alberta is still DED free.
With a proper prevention program in place which includes several components, we can keep DED at bay. We must maintain diligent at public awareness, firewood control, tree sanitation (removal of dead wood), beetle monitoring and surveillance for the disease. If a tree has tested positive for DED the tree must be removed and disposed of immediately to prevent any further spread of the disease. With a aggressive prevention program in place, Alberta has a solid foundation to keep the province free of the disease.
Prepared by: Janet Feddes-Calpas, AAFRD Dutch Elm Disease Program Coordinator
Revised December 1999. |
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