Learn to Identify Common Tree Diseases in AlbertA

Many diseases can affect your trees, whether that means stunting their growth or even causing them to die. Early detection of any disease is the best way to save your trees, so being able to identify a diseased tree is very helpful. 


To help you learn how to identify and manage common tree diseases in Alberta that affect various tree species, your Edmonton arborists at All Season Tree Service have created this helpful guide that includes information such as how to manage the symptoms. If your trees have been infected with any of these diseases, be sure to contact us and we’ll help you with a disease consultation or tree removal in Edmonton. 


Now you can use our handy search bar below to browse through some of the common tree diseases that are found in the Edmonton area and across Alberta.

White spruce

ARMILLARIA ROOT ROT – ARMILLARIA MELLEA COMPLEXE

  Location: Base of tree

  Season: Spring and summer (after damage from freezing or drought)

  Causes: Fungus

  Effects: Induces sapwood decay in affected parts and often kill trees (singularly or in patches)

  Signs: Decrease in tree vigour, dieback of branches, yellowing foliage and considerable flow of resin in conifers

  Tree species: White spruce, tamarack larch, poplars and more

  Management: Stumps of affected trees provide food source for the fungus, so remove debris, stumps and roots after cutting down affected trees

Colorado Spruce

CANKER OF SPRUCE – LEUCOSOMA KUNZEI SACC.

  Location: Trunks

  Season: Spring and fall

  Causes: Fungi

  Effects: Cankers are localized lesions that can cause deformations, dieback, growth reductions and sometimes death of trees; stem cankers lead to death while branch cankers lead to limited deformation

  Signs: Dying branches, heavy white pitch flow that produces a solid coat over the cankers and drips from branches

  Tree species: Colorado spruce, tamarack larch and white pine

  Management: Watering affected trees may alleviate stress; cut branches with reddened needles and clean shears between branches; reinvigorate the tree with balanced fertilization

Aspens tree

CYTOSPORA CANKER – VALSA SORDIDA

  Location: Trunks, annual shoots and branches

  Season: Spring and fall

  Causes: Fungus

  Effects: Initial infection is followed by death of part of the bark but rarely forms a true canker; the disease affects weakened and stressed trees

  Signs: Areas of sunken and brown dead bark, with wet, foul-smelling, discoloured wood under the bark; orange-coloured fructifications coming out of the bark

  Tree species: Balsam poplar, aspens and more

  Management: Remove wilted and dead limbs; treat all pruning cuts immediately; disinfect your pruning equipment after each cut

Maple tree

HEART ROT DISEASE – ASCOCORYNE SARCOIDES

  Location: Centre of tree

  Season: Summer and fall (after pruning)

  Causes: Fungus

  Effects: Causes tree to decay over time, which leads to branch breakage

  Signs: Presence of mushrooms and other forms of fungi around the roots or trunk of the tree

  Tree species: Maples and oaks

  Management: Minimize pruning wounds that expose heartwood and shape trees at an early age so major branch removal isn’t necessary later

Tree in summer

LARCH DWARF MISTLETOE – ARCEUTHOBIUM LARICIS

  Location: Trunk and branches

  Season: Summer

  Causes: Parasites

  Effects: Reduce wood quality, diameter and height growth and sometimes kill the tree because it provides entrance points for stain and decay producing fungi

  Signs: Branches and stems are often swollen at dwarf mistletoe infection sites

  Tree species: Lodgepole pine among others

  Management: Prune infected branches; when the trunk is infected clearcut harvesting of infected trees is necessary to ensure parasites cannot spread to other trees

Lodgepole pine

PINE NEEDLE CAST – LOPHODERMELLA CONCOLOR

  Location: Needles on conifers

  Season: Moist summers

  Causes: Fungus

  Effects: Defoliation of needles, dieback and death of branches and mortality after repeated epidemics (especially in young trees); they only affect new foliage

  Signs: Red-brown needles that eventually turn straw coloured with concolourous, oval-shaped fruiting bodies 

  Tree species: Lodgepole pine

  Management: Ensure efficient air circulation around trees and maintain good weed control; apply fungicides to protect healthy new foliage

Pine tree

RED HEART ROT – STEREUM SANGUINOLENTUM

  Location: Trunks

  Season: Summer

  Causes: Fungus

  Effects: Most often leads to destruction of tree but can be responsible for heartwood stains and terminal dieback of branches

  Signs: Fruiting body forms a crust-like layer that is cinnamon brown with a wavy edge; it turns blood red when rubbed

  Tree species: White spruce, balsam poplar, tamarack larch, pines and firs

  Management: Once established it cannot be effectively treated; prevent by avoiding unnecessary damage or injuries from pruning

BRONZE LEAF DISEASE

BRONZE LEAF DISEASE – APIOPLAGIOSTOMA POPULI

  Location: Leaves

  Season: Spring/Summer

  Causes: Fungus

  Effects: Without proper management, an infected tree can die within 3-5 years

  Signs: Infected leaves turn orange-brown to reddish-brown with colouration starting at the edges of the leaf and moving inward toward the base. A defining characteristic of the disease is the way that the leaf veins and petiole often remain a bright green in stark contrast to the rest of the leaf.

  Tree species: Poplars

  Management: Bronze Leaf lives inside a tree and, once established, cannot be eradicated. The only treatment is containment, which is accomplished by removing affected branches or, at last resort, the tree itself.

ELM SCALE

ELM SCALE – GOSSYPARIA SPURIA

  Location: Smaller limbs that are higher on the tree

  Season: Spring

  Causes: Insects

  Effects: Heavy infestations may kill weakened trees and cause branch dieback in healthy trees

  Signs: A sooty, grayish/black mould on leaves, as well as honeydew that can spread to coat nearby structures and vehicles

  Tree species: Elm, hackberry

  Management: European Elm Scale is easily treated with soil-applied insecticides, as well as systemic products that are applied at the base of the tree and distributed through the root system. By law, Elms in Calgary should only be pruned between October 1st and March 31st in order to prevent the spread of Dutch Elm Disease.

FIRE BLIGHT

FIRE BLIGHT – ERWINIA AMYLOVORA

  Location: Limbs, trunk, root system, flower clusters

  Season: Spring

  Causes: Bacteria

  Effects: Fire blight can destroy limbs and even entire trees

  Signs: Early indications of fire blight include a light tan to reddish, watery ooze coming from an infected branch, twig, or trunk cankers. Flowers wilt and turn brown, twigs shrivel and blacken, and in advanced cases, cankers begin to form on branches.

  Tree species: Fruit trees: Apple, pear, quince, crabapple, etc.

  Management: There is no known cure for Fire Blight; the only effective treatment is regular pruning to remove infected stems and branches, although spraying of bactericide chemicals can reduce the bacteria’s ability to survive and reproduce. Pruning can also be a means of transmission; it is critical that you sanitize your tools as you prune.

OYSTERSHELL SCALE

OYSTERSHELL SCALE – LEPIDOSAPHES ULMI

  Location: Bark on trunk and limbs

  Season: Spring

  Causes: Insects

  Effects: Heavy Oystershell Scale populations on limbs and twigs are not only unattractive but will also weaken the tree and make it more susceptible to further disease and damage.

  Signs: Oystershell shaped bumps on branches, leaves that are turning yellow, branch dieback

  Tree species: Fruit trees, lilac, ash, maple, dogwood, poplar, and willow

  Management: This pest reproduces only once per year, during a period of approximately 10 days occurring in early to mid-June. Horticultural oil can be applied at this time in an effort to suffocate the pest inside its permanent shell. Natural remedies include the introduction of natural predators of oystershell scale, such as ladybugs or lacewings. Pruning is often the most effective remedy.

DUTCH ELM DISEASE – OPHIOSTOMA NOVO-ULMI

DUTCH ELM DISEASE – OPHIOSTOMA NOVO-ULMI

  Location: Leaves, branches, roots

  Season: Summer

  Causes: Fungus spread by elm bark beetles

  Effects: Starvation of the tree roots

  Signs: Withering and yellowing of leaves on the upper branches during the summer months that spreads and causes branches to dieback

  Tree species: Elms

  Management: Because elm bark beetles represent the primary mode of Dutch Elm Disease infection, insecticides such as Arbotect are often used to provide ongoing control. An alternative and less effective method involves the injection of a fungicide into the base of the tree, using specialized equipment. Disinfect any tools used on diseased trees.

OAK WILT – BRETZIELLA FAGACEARUM

OAK WILT – BRETZIELLA FAGACEARUM

  Location: Starts at the crown and spreads to lower branches, limbs, and roots

  Season: Spring/Summer

  Causes: Fungus

  Effects: Wilting of leaves and limbs and eventual tree death

  Signs: An oily green appearance in sections of the tree’s canopy, which rapidly turns a tan or red colour

  Tree species: Oak

  Management: There is no permanent cure for Oak Wilt, so prevention offers the most likely method of control. Do not prune oak trees in the spring and summer months; take care to protect susceptible trees from injury during this period and use tree paint to cover any wounds that might occur. Injections of propiconazole, a fungicide, into the roots can help prevent transmission, as well.

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All Season Tree Service

All Season Tree Service

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