Forest health: pests, diseases and severe weather conditions
What you need to know about pests, diseases and severe weather conditions that affect forest health in Ontario.
Spongy moth and other defoliators
Learn about common caterpillars that strip the leaves from trees and shrubs, and what you can do to protect your property.
Think your trees have a forest health problem? Contact a local arborist for confirmation and treatment options.
Pests
Asian long-horned beetle
An invasive wood borer.
Aspen twoleaf tier
An insect that mainly feeds on aspen trees.
Birch casebearer
An invasive insect that feeds on birch and alder.
Birch skeletonizer
An insect that feeds on the leaves of birch trees.
Cedar leafminer
A group of insects that feeds on the insides of cedar foliage.
Eastern larch beetle
A beetle that burrows under the bark of tamarack (larch) trees.
Emerald ash borer
An invasive beetle that kills ash trees.
Forest tent caterpillar
An insect that eats the leaves of hardwood trees.
Hemlock woolly adelgid
An invasive insect that causes hemlock trees to lose their needles.
Jack pine budworm
An insect that eats jack pine needles.
Larch casebearer
An invasive insect that hollows out larch needles.
Large aspen tortrix
An insect that eats the leaves of hardwood trees like aspen and birch.
Pine false webworm
An invasive insect that eats the needles of pine trees.
Satin moth
An invasive insect that damages poplar and willow trees.
Spongy moth
An invasive insect that feeds on hardwoods.
Spruce budworm
An insect that eats spruce and fir needles.
Diseases
Armillaria root rot
A fungal disease that kills trees.
Beech bark disease
An invasive fungal-insect complex that kills beech trees.
Beech leaf disease
A disease possibly caused by a worm-like nematode.
Brown spot needle blight
A disease that damages pine trees.
Butternut canker
An invasive disease that kills butternut trees.
Dogwood anthracnose
An invasive disease that damages dogwood trees.
Dutch elm disease
An invasive disease spread by a beetle that kills elm trees.
Oak wilt
An invasive fungal disease that kills oak trees.
Septoria leaf spot of birch
A fungal disease common in wet years.
White pine blister rust
An invasive disease that kills white pine, especially young trees.
Severe weather conditions
Blowdown
Localized tree fall caused by extreme wind/weather events.
Drought damage
Browning caused by prolonged periods of dryness.
Snow damage
Heavy snow loads weighing down trees, often breaking tops and branches.
Winter browning
Needle browning or loss caused by warm weather in winter followed by extreme cold weather in spring.