Tree care

Elm trees are at risk. The most serious threat comes from Dutch Elm Disease (DED), which is a fatal fungal disease that infects only elm trees. Bark beetles spread the disease from infected to weakened trees and can kill a tree in as little as three weeks. Beetles are active between April 1 – Sept. 30 and are attracted to the scent of fresh cut trees. The annual pruning ban of elm trees during this time is in place to help keep the risk of DED low.

Learn more about Dutch Elm Disease 

• Black knot affects Schubert Chokecherries, May Days, Saskatoons, etc.
• Black knot is a highly contagious fungal disease and can cause branch die-back or even kill your entire tree if left unchecked.
• To get rid of this unpleasant looking disease, prune the infected branch 20-30cm below the ‘knot’ (pictured above).
• Sterilize pruning tools with hand sanitizer or rubbing alcohol between each cut.
• The diseased wood must be pruned and either burned, buried or put in a tiedplastic garbage bag.

• Fire blight is a bacterial disease that affects members of the Rosaceae family, including Cotoneaster, Apple, Crabapple, Pear, Rose, Hawthorne, Mountain Ash, etc.
• Flowers and leaves turn brown/black and twigs curl in to a "shepherd's hook". Leaves will remain on the tree well into the winter. Cankers appear as discoloured/sunken patches on branches or trunk. If cankers appear on the main trunk of your tree it may need to be removed.
• Remove infected tissue and healthy tissue back along an affected branch at least 30-45cm. *Sterilize all pruning tools between each cut. (Bleach:Water = 1:9)
• All diseased material must be burned or sealed in a garbage bag and discarded.
• Fire blight transmits very easily from plant to plant by contaminated pruning tools, hail wounds, birds, or rain splashes.

• Bronze leaf (BLD) is a fungal disease that currently affects Swedish columnar aspen and Tower poplar. There is concern that it could jump to our native Trembling aspen which could be devastating to the Aspen parkland region that we live in.
• BLD enters through the leaves and becomes systemic after that, meaning it can spreadvery quickly.
• Affected branches turn a reddish/bronze colour, while the veins of the leaves remain green. Those leaves will remain on the tree well into the winter. They contain spores that will spread to new hosts the following spring.
• Affected branches should be removed back to the trunk of the tree and pruning tools should be sanitized with bleach: water 1:10 solution between each cut.
• The diseased wood and leaves should be bagged and disposed of.

• Dutch Elm Disease (DED) is a fungal disease that is carried by the insect vector the elm bark beetle which is native to our area. Beetle bore into the bark of American Elm trees and spread the fungus.
• DED can be first noticed by yellow dying branches in the canopy and can quickly kill entire stands of elm trees.
• DED is not currently in Alberta but can be easily spread here through fire wood transportation as is it is currently wreaking havoc to the East (Saskatchewan) and in the States south of us.
• DED containment is legislated by the Government of Alberta through the Agricultural Pests Act.

• Rusts are fungal infections that affect conifers like spruce or pine.
• Needles will appear covered in an orange powdery substance and may drop.
• Prune all affected parts and ensure good clean-up of all needle drop around trees.

• A fungal disease that affects caragana, aspen, hawthorn, currant, turf grass, etc.
• Powdery mildew favours cold, moist shady conditions and can be controlled by eliminating those conditions. E.g. Pruning to increase air flow, reduce watering.
• Ensure leaf litter is cleaned up well and consider spraying a fungicide for large infestations.
• The mildew does not actually kill the plant but shades the leaf and doesn’t allow sunlight in thereby starving the plant.

• Cytospera is a fungal infection that affects Spruce trees.
• It is identified by dead branches that always die-back from the bottom of the tree up. When close up you will notice pale mauve oozing lesions.
• Known as the slow killer, it can take many years to completely kill a spruce but the tree will eventually die if the disease is not managed.
• Prune out and remove and dead or infected wood. Good sanitation in your yard will prevent the spread.

• Hypoxylon canker is a fungal disease that affects Aspen and Balsam Poplar.
• The spores are active during late summer and fall, so avoid pruning in August and September.
• Swollen distorted areas on branches or the trunk will be discoloured and show a grey and white camouflage pattern.
• Prune any affected areas which may include entire trees if the canker is in the trunk.
• A canker left on a trunk creates a weakened area that is prone to breaking.

• Wood decay is a fungal infection that can be identified by the fruiting bodies growing off the trunk or branches of the tree or up from the soil over root zone of the tree.
• Decay enters through poor pruning cuts and bark damage from mowing, trimming or planting too deeply. By avoiding any unnecessary bark damage you can largely prevent decay fungi.
• It is important to call in an arborist to identify the type of wood decay present because conks can often indicate the tree or part of the tree is likely to fail.

• Slime flux is a bacterial wetwood disease that commonly affects Poplar and Elm. It is characterized by smelly ooze dripping out down the bark.
• It is spread by wind, insects, pruning tools etc. to a point of entry. (i.e. a pruning or hail wound)
• While slime flux is unsightly is rarely causes any real damage to a tree.