The majority of Airdronians are aware of the significant advantages trees offer to individuals and our community. The fundamentals of caring for trees are less well known, though. 

The city of Aridrie has a fact sheet of all the tree diseases that have been in Airdrie at one point or another. 

To see pictures of each disease listed below, click the link above. 

Black Knot 

  • May Days, Saskatoons, Schubert Chokecherries and more are all impacted by black knot. If left untreated, the extremely contagious fungal disease known as black knot can lead to limb die-back or even the death of your entire tree. Pruning the affected branch 20–30 cm below the 'knot' will help get rid of this unsightly condition. Between each cut, clean pruning tools with hand sanitizer or rubbing alcohol. It is necessary to remove the sick wood and either burn, bury, or place it in a knotted plastic rubbish bag. 


  • Members of the Rosaceae family, such as Cotoneaster, Apple, Crabapple, Pear, Rose, Hawthorne, Mountain Ash, etc., are susceptible to the bacterial disease known as "fireblight." Flowers and leaves change to a brown or black colour, and twigs begin to twist into "Sheppard's hooks." Long into the winter, the tree's leaves will still be there. Cankers show up on branches or the trunk as discoloured areas. Healthy tissue should be removed back along the branch at least 30 to 45 cm. All diseased stuff needs to be burnt or put in a rubbish bag before being thrown away. Plant-to-plant transmission of fire blight is made very simple by infected pruning tools, hail damage, birds, or raindrops. 

Bronze leaf Disease 

  • Swedish columnar aspen and Tower poplar are currently affected by the fungus disease known as bronze leaf (BLD). There are worries that it might spread to our local Trembling aspen, which would be disastrous for the Aspen parkland area where we live. BLD spreads quickly because it enters through the leaves and then becomes systemic. While the veins of the leaves continue to be green, affected branches take on a reddish-bronze hue. The tree will have those leaves on it late into the winter. The spores that will spread to new hosts the following spring are contained in them. Affected limbs should be taken back to the tree's truck, and pruning equipment should be cleaned with a bleach-to-water-to-bleach solution every time they are used. The diseased wood and leaves should be bagged and disposed of. 

Dutch Elm Disease 

  • The elm bark beetle, a local insect vector that transmits the fungus Dutch Elm Disease (DED), is a disease that affects trees. The fungus was transmitted by beetles that bored into the bark of American elm trees. DED can quickly kill large stands of elm trees and is initially identified by yellow, dead branches in the canopy. As it is currently inflicting havoc to the East (Saskatchewan) and in the States South of us, DED is not currently in Alberta but can be readily introduced here through the transportation of firewood. 

Needle Rusts 

  • Conifers like spruce or pine can have rusts, which are fungal infections. Needles may drop and seem covered in an orange-colored powdered material. Prune all affected parts, and ensure good clean-up of all needle drops around trees. 

Powdery Mildew 

  • The caragana, aspen, hawthorn, current and turf grass are all affected by this fungus. Eliminating the chilly, wet, and shaded circumstances that powdery mildew prefers will help control it. For instance, pruning to improve airflow, reducing watering, making sure leaf litter is cleaned up thoroughly, and thinking about using a fungicide for serious infestations. The mildew shadows the leaf and prevents sunlight from penetrating, starving the plant but not actually killing it. 

Cytospera Canker 

  • Spruce trees can become infected with Cytospera, a fungus. Dead branches that always die-back upward from the base of the tree serve as a telltale sign. Lesions that are pale mauve and that are leaking can be seen up close. The so-called "slow killer" can take several years to totally destroy a spruce tree, but if the disease is not controlled, the tree will finally die. Remove and prune any dead or diseased wood. Your yard's cleanliness will stop the spread. 

Hypoxylon Canker 

  • Aspen and Balsam Poplar are both afflicted by the fungal disease known as hypoxyln canker. Avoid trimming in August and September as the spores are active during the late summer and early fall. On branches or the trunk, swollen, distorted portions will be discoloured and display a grey and white camouflage pattern. If the canker is in the trunk, prune all affected regions, which may include whole trees. A canker left on a trunk weakens it and makes it more likely to break. 

Wood Decay 

  • The fruiting bodies that are emerging from the tree's trunk, branches, or soil above the root zone can be used to detect wood rot, a fungal infection. Poor pruning cuts and bark damage from cutting, mowing, or planting too deeply allow decay to enter. You may primarily avoid decay fungi by preventing any unnecessary bark damage. Conks can frequently be a sign that a tree or a section of a tree is going to fail, thus it's crucial to call in an arborist to determine the sort of wood rot present. 

Slime Flux 

  • Poplar and Elm are frequently afflicted by the bacterial wet wood disease known as slime flux. It is distinguished by foul slime that drips out along the bark. It spreads to the point of entrance by wind, insects, and pruning instruments. Although slime flux is ugly, it rarely actually harms a tree. 

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