Common Tree Diseases Found in Alberta
Learn to Identify Common Tree Diseases in Alberta
Many diseases can impact your trees, leading to stunted growth or death. Early detection is crucial for saving your trees, so it is essential to identify a diseased tree.
The professional arborists at All Season Tree Service have created this helpful guide to assist you in recognizing and managing common tree diseases in Alberta that affect various tree species. It includes information on how to manage symptoms effectively. If your trees get infected with any diseases, please contact us for a disease consultation or tree removal in Edmonton.
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ARMILLARIA ROOT ROT – ARMILLARIA MELLEA COMPLEXE
Location: Base of tree
Season: Spring and fall
Causes: Fungus
Effects: Induces sapwood decay in affected parts and often kills 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 a food source for the fungus, so remove debris, stumps and roots after cutting down affected trees
CANKER OF SPRUCE – LEUCOSTOMA 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
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
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 significant branch removal isn’t necessary later
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
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 reasonable weed control; apply fungicides to protect healthy new foliage
RED HEART ROT – STEREUM SANGUINOLENTUM
Location: Trunks
Season: Summer
Causes: Fungus
Effects: Most often leads to the destruction of the tree but can be responsible for heartwood stains and terminal dieback of branches
Signs: The 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 – APIO PLAGIOSTOMA 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 how 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, accomplished by removing affected branches or, at last resort, the tree itself
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: The European Elm Scale is easily treated with soil-applied insecticides and systemic products applied at the tree's base and distributed through the root system. By law, Elms in Calgary should only be pruned between October 1st and March 31st to prevent the spread of Dutch Elm Disease
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 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: Fire Blight has no known cure; the only effective treatment is regular pruning to remove infected stems and branches. Although spraying bactericide chemicals can reduce the bacteria’s ability to survive and reproduce, pruning can also be a means of transmission; you must sanitize your tools as you prune
OYSTERSHELL SCALE – LEPIDOSAPHES ULMI
Location: Bark on trunk and limbs
Season: Spring
Causes: Insects
Effects: Heavy Oystershell Scale populations on limbs and twigs are unattractive, 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 yearly, for approximately 10 days in early to mid-June. Horticultural oil can be applied at this time to suffocate the pest inside its permanent shell. Natural remedies include the introduction of natural predators of oyster shell scale, such as ladybugs or lacewings. Pruning is often the most effective remedy
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 often provide ongoing control. An alternative and less effective method involves injecting a fungicide into the tree's base using specialized equipment. Disinfect any tools used on diseased trees
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: Oak Wilt has no permanent cure, so prevention is the most likely control method. 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 also help prevent transmission
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