Calgary Arborist – News & Resources

Alberta Elm Pruning Ban Starts April 1st – 14/03/10

Alberta Elm Pruning Ban Starts April 1st in Alberta.

Right here and now in Calgary there is a behind the scenes battle going on with a tree disease that has preyed on our Elm stands in North America for many years. Luckily we have remained free of Dutch Elm Disease, due in no small part to the hard work done by local professional Arborists and in particular; The Society to Prevent Dutch Elm Disease (StopDED). They work hard to prevent the spread of the disease through public education and the development of policies and bylaws such as the “do not transport firewood” signs at provincial borders, and the provincial Elm Pruning ban which runs from April 1st through to September 31st annually.

You see, the disease is spread by a beetle that bores into the bark of Elm trees. There are three types of beetle currently considered “vectors” . A vector is an organism that carries disease-causing microorganisms from one host to another. Keeping these beetles at bay is key in preventing the spread of the disease. Elm bark beetles, responsible for spreading the deadly Dutch Elm Disease fungus, feed on healthy elms and breed in dead and dying elm trees and Elm firewood and brush piles.

The Pruning Ban

When Elm trees are pruned during the pruning ban period, pheromones are released by the tree which attract these beetles, which are active at this time and will attack an otherwise healthy Elm. This can infect it with Dutch Elm Disease. The disease is serious and spreads quickly, once an elm tree is infected with Dutch Elm Disease it will die, usually within a year. The first signs can be “flagging” in the crown. Flagging is the wilting and deterioration of major limbs in the tree canopy due to damage caused by the disease.

“Flagging” in an American Elm
Flagging in Elm (Dutch Elm disease)
Steven Katovich, USDA Forest Service,

So you may ask yourself; “Why are they still being sold and planted?”. All you have to do to answer this question is to consider the key points and features of the tree to realize it’s value:

  • Above average growth rate
  • Stately, cascading form when mature
  • Grows well in a wide variety of soils (such as our clay based, alkaline soil)
  • Tolerant of drought
  • High salt tolerance when planted near roads (road and sidewalk salt can kill some tree species)
  • Thrives despite our extreme local climate
  • Long Lifespan


What can you do?

There are many things you can do to keep your tree healthy and free of problems such as Dutch Elm Disease

  • Keep your elm tree healthy, and properly pruned
  • Water throughout the summer, ending in August, water again around halloween or just before freeze up to ensure sufficient soil moisture for the following spring
  • Have dead and damaged branches removed properly to reduce breeding sites for the beetle
  • Prune only between October 1st and March 31st to prevent pheromone release that can attract the beetles that carry the disease.
  • After pruning ensure all Elm wood is disposed of properly through disposal at a landfill or by burning or chipping of the material as the wood is a great place for the insect to re-produce
  • Report suspected diseased trees to the StopDED office or contact them via email

If you are concerned about Dutch Elm disease, think your tree may be infected or just want more information regarding the disease feel free to contact us through our website to contact our team of qualified Arborists to help assess your trees needs.

4 comments… add one
  • Peter

    August 1, 2011, 10:44 pm

    I live in a new community and many of the homes had american elm’s planted in front. Most look like they are sick, having light green leaves and no new foliage since the spring buds matured. Any suggestions on how to nurse these trees back to health?

    • MattD

      August 21, 2011, 9:37 am

      There are many issues that could cause these symptoms. Likely if it widespread throughout the community, it would be either climatic or weather related. However if all the trees were planted at once by the developer, it could also be related to the quality of planting. However it would be easiest to come out to have a look.

  • CLewis

    May 7, 2016, 8:16 pm

    We live in Lethbridge Alberta and our American Elms do not look well. They have smaller leaves than usual and in many places the leaves did not form and the buds are dried and breaking off. We recently had a heavy frost as the tree was budding. Could this be the cause or should I look further into the health of the tree.
    Thank you for your help

    • Matt Davis

      May 14, 2016, 8:23 am

      I would suggest getting in touch with a certified Arborist in Lethbridge to have a look and provide recommendations. Make sure that the arborist you choose is certified by the ISA however. If you would like a referral please let us know and we would be happy to provide one.

      The Adair Tree Care Team.


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