Wednesday, November 25, 2009

Bronze leaf disease infecting Calgary's trees

A fungal disease is killing trees in Calgary, often within three to five years of being infected.

Bronze leaf disease attacks poplar species and hybrids; particularly trembling aspen, Swedish columnar aspen and tower poplar. Because of the rapid and high kill rate among infected trees, early detection and treatment is important and may not only save trees but prevent the disease from spreading. There are currently no known chemical controls for this fungus.

“The City is in the process of identifying the scope of bronze leaf disease in Calgary and is monitoring, diagnosing and treating blighted City-owned trees,” said Russell Friesen, Calgary’s urban forestry coordinator.

Friesen added that The City needs the cooperation of the public to fight this deadly fungus.

“Citizens need to recognize symptoms and contact a local tree care professional for diagnoses and treatment,” he said.

Bronze leaf disease spreads from one tree to the next via airbornespores, which disperse in early spring.

Infected trees can be recognized by these symptoms:

- Diseased leaves often first show up in the lower crown but may be scattered throughout the crown of the tree or isolated to a few branches.

- Leaves become dark reddish-brown, chocolate brown or bronze although the veins and the leaf stem may remain green for some time.

- Infected leaves remain on the tree through winter.

- Once the disease spreads, browning may be observed under the bark of diseased branches.

- New leaves on infected branches may appear underdeveloped in subsequent years.

Infected branches should be taken to a City of Calgary landfill for proper disposal. They should not be chipped, composted or used for firewood.

Here is a video of Russell Friesen explaining bronze leaf disease and how to combat it. For more information please visit

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