“The intent of the week is to raise awareness on how dangerous Dutch elm disease is, the importance of elm trees to our communities, and that DED can be prevented,” says Janet Feddes-Calpas, executive director, Society to Prevent Dutch Elm Disease (STOPDED). “At present, Alberta has the largest DED-free American elm stand in the world and it’s important to protect this valuable resource. STOPDED is asking for your assistance to save our beautiful elm trees from this deadly disease.”
DED is caused by a fungus that clogs the elm tree's water conducting system, causing the tree to die. The fungus is primarily spread from one elm tree to another by three species of beetles - the smaller European, the native, and the banded elm bark beetle. The beetles are attracted to weak and dying trees that then serve as breeding sites for the beetles. Once the beetles have pupated and turned into adults, they leave the brood gallery and fly to healthy elms to feed, thus transporting the fungus on their bodies from one tree to the next.
“Monitoring for the beetles is done annually throughout the province by STOPDED,” says Feddes-Calpas. “The smaller elm bark beetles have been found throughout the province in low numbers and now the banded elm bark beetle is found in larger numbers throughout the City of Medicine Hat and area. This demonstrates that we must be even more vigilant.”
Leaves on a DED-infected elm will wilt or droop, curl and become brown. “This appears in mid-June to mid-July,” says Feddes-Calpas. “Leaves on trees infected later in the season usually turn yellow and drop prematurely. Leaf symptoms are accompanied by brown staining under the bark. All DED suspect elms must be tested in a lab, so if you think you see DED symptoms call the STOPDED hotline at 1-877-837-ELMS.”
What can you do?
- Be aware of the Alberta elm pruning ban between April 1 and September 30. The beetles are most active at this time and can be attracted to the scent of fresh tree cuts, possibly infecting a healthy elm.
- Keep your elm trees healthy, and vigorous.
- Water elms well from April to mid-August. To allow the tree to harden off for the winter, watering should be stopped mid-August followed by a good soaking or two before freeze-up.
- Only between October 1 and March 31, remove dead branches and trees as they can provide beetle habitat.
- Dispose of all elm wood immediately by burning, burying or chipping.
- Report all suspect trees to the DED Hotline at 1-877-837-ELMS. A confirmed DED tree must be removed immediately to prevent further spread.
What you shouldn’t do:
- Do not transport or store elm firewood at any time! DED and the beetles are declared pests under the Alberta Agricultural Pests Act and this can be enforced.
- Do not transport elm firewood into Alberta! Firewood is confiscated at all the Alberta-Montana border crossings.
- Do not prune elms between April 1 and September 30.
Agri-News is a regional and provincial news package published each Monday by Alberta Agriculture and Forestry. It has information of interest to Albertans on agriculture, food and beverage production, marketing, research, provincial events and policy, and home gardening. Get your free subscription of the Agri-News: This Week in Agriculture weekly mailout
Ken Blackley, Agri-News editor
Alberta Agriculture and Forestry
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