Common Pests and Tree Diseases in Ontario
This article will tell you about some of the major threats to trees in our area from pest and tree diseases in Ontario.
There are a number of common pests and tree diseases in Ontario that pose a risk to trees in Toronto City, York Region, Durham Region, Northumberland County, Peterborough and Kawartha Lakes. Do you know the signs of a problem with the health of your trees?
The tree canopy of Toronto City, the GTA, Durham and York Regions is vitally important to our quality of life as well as an essential part of combating climate change. However, maintaining the health of our urban forests means we all have to be vigilant to the potential threats posed by common pests and diseases that target various tree species. In this guide, we will explore the specific trees found in our region and highlight which pests and diseases threaten them. We’ll highlight the early signs of infestation so you know what to watch out for. As is often the case, prevention is better than cure, so we’ll also tell you what you need to do to keep your trees healthy and protect them from these threats.
Common Tree Species in the Greater Toronto Area, Durham Region and York Region
Maple Trees:
- Species: Sugar Maple (Acer saccharum), Red Maple (Acer rubrum), Silver Maple (Acer saccharinum).
- Commonly Found: Throughout the GTA, Durham Region, and York Region.
- Susceptibility: Vulnerable to various pests and diseases
Oak Trees:
- Species: Northern Red Oak (Quercus rubra), White Oak (Quercus alba), Bur Oak (Quercus macrocarpa).
- Commonly Found: Predominantly in the GTA and York Region.
- Susceptibility: Oak-specific pests and diseases.
Ash Trees:
- Species: Green Ash (Fraxinus pennsylvanica), White Ash (Fraxinus americana).
- Commonly Found: In the GTA, Durham Region, and York Region.
- Susceptibility: Particularly vulnerable to the Emerald Ash Borer.
Spruce Trees:
- Species: Colorado Blue Spruce (Picea pungens), White Spruce (Picea glauca), Norway Spruce (Picea abies).
- Commonly Found: Widely distributed in the GTA, Durham Region, and York Region.
- Susceptibility: Prone to specific pests and diseases.
Pine Trees:
Species: Eastern White Pine (Pinus strobus), Scots Pine (Pinus sylvestris).
Commonly Found: Throughout the regions.
Susceptibility: Faces threats from various pests.
Pests and Tree Diseases in Ontario Threatening Trees in the GTA, Durham Region, and York Region
These are some of the pests and tree diseases in Ontario that pose a risk to trees in our area:
- Dutch Elm Disease (DED): A fungal disease affecting elm trees, transmitted by bark beetles
- Emerald Ash Borer (EAB): An invasive beetle species that attacks and kills ash trees
- White Pine Blister Rust: A fungal disease that affects white pines, causing cankers and reducing tree vigor
- Asian Long Horned Beetle: An invasive beetle species that poses a threat to hardwood trees
- Oak Wilt: A vascular wilt disease affecting oak trees, caused by a fungus and transmitted by beetles
- Gypsy/Spongy Moth Infestation: An invasive moth species that can defoliate trees, including oaks and aspen
- Beech Bark Disease: A complex disease involving both a scale insect and a fungus affecting beech trees
- Needle Cast: Fungal diseases infect needles, leading to needle drop and potentially death of the tree
- Maple Dieback or Maple Decline: A condition characterized by the gradual decline of maple trees, often due to multiple stressors
Protecting your trees from pests and tree diseases in Ontario
Recognizing the early signs of pest infestation or disease is crucial for timely intervention and protection of our urban forests. Look for these common signs of a problem:
- Leaf discoloration – early yellowing or browning of leaves may indicate stress or disease. Spots or patches on leaves
- Broken, cracked branches or peeling bark
- Unusual growth patterns – stunted or distorted growth can be a sign of both pests and diseases
- Cankers and lesions – presence of lesions or cankers on the bark may indicate fungal infections.
- Wilting and defoliation – premature wilting or defoliation suggests a potential infestation.
- Presence of pests – sightings of the actual pests or their larvae, egg masses, or boreholes.
- Presence of insects or rodents – greater numbers of wasps or other insects near the tree, signs of rodent activity.
9 signficant pests and tree diseases in Ontario
Let’s take a look at some of the significant pests and diseases affecting key tree species in the Greater Toronto Area (GTA), Durham Region, and York Regions of Ontario.
1. Emerald Ash Borer (Agrilus planipennis)
Trees Affected: All species of Ash trees in Ontario.
The invasive Emerald Ash Borer (EAB) poses a severe threat to Ontario’s ash trees, including White Ash, Green/Red Ash, and Blue Ash. EAB infestations disrupt the tree’s vascular system, causing irreversible damage and often leading to tree death. Early signs include thinning canopies, defoliation, dieback of branches, and woodpecker activity.
Prevention:
Avoid transporting infested wood
Regularly inspect ash trees for signs of the presence of the distinctive metallic green beetle.
Treatment:
Treatment options are most effective in the early stages but it is rarely detected in time
Removal and replacement may be necessary in advanced cases or to protect nearby trees not yet affected.
2. Gypsy/Spongy Moth (Lymantria dispar)
Trees Affected: Broadleaf trees such as oaks, maples, poplars, and birches.
Gypsy or Spongy moths cause defoliation, weakening trees. Early signs include leaf damage and silken threads produced by larvae. Egg masses on trunks or branches are indicative of infestation.
Prevention:
Maintain tree health through regular pruning.
Reduce bark wounds to deter moth attacks.
Treatment:
Prune infected branches promptly.
Remove egg masses and use biological insecticides.
3. Dutch Elm Disease (Ophiostoma novo-ulmi)
Trees Affected: All Elm species in Ontario.
Dutch Elm Disease (DED) affects elms, spreading through beetles. Early symptoms include wilting leaves and yellowing. Later signs include branch and trunk cankers, leading to tree decline and eventual death.
Prevention:
Avoid pruning elms during the growing season.
Remove and destroy infected elm wood.
Treatment:
Monitor for signs of infection throughout the summer.
Prune infected branches promptly.
Remove dead branches and trees from the site.
4. White Pine Blister Rust (Cronartium ribicola)
Trees Affected: Primarily White Pines, especially Eastern White Pine.
White Pine Blister Rust impacts white pines, causing cankers and disrupting tree functions. Early signs include yellow-orange spots on needles, while later signs involve cankers, resin secretion, and a sparse canopy.
Prevention:
Select resistant tree varieties for planting.
Thin and selectively harvest white pines.
Treatment:
Regularly check trees for symptoms.
Prune infected branches promptly.
Remove and destroy infected trees.
5. Asian Longhorned Beetle (Anoplophora glabripennis)
Trees Affected: Maples, birches, poplars, willows.
The Asian Longhorned Beetle poses a threat to hardwood trees. Signs include egg-laying pits, sap, wilting leaves, and later, exit holes and canopy dieback.
Prevention:
Regularly check trees for signs.
Report infestations promptly.
Treatment:
Infested trees should be cut down.
Burn or chip felled trees to eliminate larvae.
6. Beech Bark Disease
Trees Affected: American beech (Fagus grandifolia) and European beech (F. sylvatica L.).
Beech Bark Disease results from scale insect and canker fungus interaction, leading to cankering, deformity, and tree death.
Prevention:
Avoid transporting firewood from affected areas.
Maintain good tree health and biodiversity.
Regularly inspect for signs of scale insects in early summer.
Be vigilant for cankers in late summer or early fall.
Treatment:
Removal of scale insects is crucial to prevent the fungus
Once fungus is present, tree removal is necessary.
7. Needle Cast
Trees Affected: Pines, Spruce, particularly the Colorado Blue Spruce and White Spruce, Douglas Fir, True Fir
Needle cast diseases are common fungal diseases affecting various tree species, leading to premature needle loss, diminished tree vitality and eventually the death of the tree.
Prevention
Improve tree health through proper pruning, watering and nutrition.
Thin trees that are too close together.
Treatment
Pruning out affected branches at the first sign of yellowing and then browning needles on the lower branches.
Removal of the tree if the disease has spread.
8. Oak Wilt
Trees Affected: All species of oak are susceptible
Oak wilt is caused by a fungus that disrupts the tree’s water-conducting vessels, ultimately leading to wilting and death.
Prevention
Promote good tree health through regular pruning
Do not prune trees during the growing season
Treatment
Break the root connection with nearby trees
Remove infected trees to prevent its spread to healthy trees
9. Maple Dieback/Decline
Trees Affected: Eastern sugar maple (Acer saccharurn), Norway maple (A. platanoides) and red maple (A. rubrum)
Not a disease as such, maple dieback has been attributed to poor environmental conditions and pollution.
Prevention and Treatment:
To protect urban maples ensure a good tree maintenance regime including watering, fertilizing and pruning to promote tree health
