Friday, August 6, 2010

Help Prevent Dutch elm disease

Calgarians can help Alberta to continue to boast the largest stand of Dutch elm disease-free American elms in the world.

Dutch Elm Disease is a fungus that clogs the tree's water conducting system, causing it to die.

This fungus is primarily spread from one elm tree to another by the European elm bark beetle. This beetle is attracted to weak and dying trees because they serve as breeding sites. Once the beetles mature, they fly to healthy elms to feed, and in doing so, transport the fungus on their bodies from one tree to the next.

What are the symptoms?
Leaves on an infected elm will wilt, droop, curl, become yellow and brown and may drop prematurely. Leaf symptoms are accompanied by brown staining under the bark. (Don’t confuse this with the onslaught of yellowing leaves due to the arrival of Autumn).

What can you do?

  • Respect the recommended province-wide elm tree pruning ban. The City of Calgary and other municipalities recommend citizens to not prune elm trees between April 1 and September 30. The beetles are most active at this time and are attracted to the scent of fresh tree cuts. Pruning during this timeframe can spread the disease. 
  • Keep your elms healthy; healthy plants are in a better position to fend off pests and infections. Good health is encouraged through proper maintenance which includes pruning, watering and fertilizing.
  • Water elms from April through mid August. To prepare the tree for winter, regular watering should cease in mid August, followed by a good soaking in mid to late September.
  • Remove dead elm branches and trees between October 1 and March 31, as they can provide beetle habitat. Dispose of all elm wood immediately at a local landfill.
  • Transporting elm firewood with the bark into Alberta is prohibited. Customs officers are trained to recognize elm firewood and will not allow this type of wood into Alberta.

Through its membership with a non-profit organization called the Society to Prevent Dutch Elm Disease (STOPDED), The City is helping to monitor Calgary’s elm trees for possible DED symptoms. There have not been any reported cases of DED in Calgary and the only reported case in Alberta occurred in the late 1990s.

Calgarians can help by monitoring the elm trees in their communities and yards. For City-owned trees displaying symptoms, please contact 3-1-1. For privately owned elm trees with symptoms, please contact your local tree care professional and call 3-1-1 to report confirmed cases.

Calgary’s elm trees not only provide shade and aesthetic appeal, they are an important part of Calgary’s urban forest, which is one of the assets that make this city a great place to live, work and play.

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