The death of external parts of a tree, like the twigs on the end of branches.
The removal of a strip of bark around the entire tree.
Invasive insect species are non-native insects that have been introduced to Ontario and North America. Without natural predators, these insects can reproduce to outbreak levels and may need additional control measures such as pesticide intervention to manage their population growth. At outbreak levels, invasive insects may cause damage to environments.
The following insects are invasive to Toronto:
Learn about invasive plant species control.
Native insect species are insects that live or grow naturally in a region without direct or indirect human intervention.
In most cases, if pruning is done to promote the health of a tree a permit is not needed. If significant pruning needs to be done or you are unsure, call 311 to see if you require a permit to remove or injure a tree.
Aphids are small soft-bodied insects that feed on plants by sucking sap from leaves and stems.
They do not cause significant damage to trees but they can make them vulnerable to other insects and diseases.
Management program in effect.
The Asian longhorned beetle is a very serious threat to the hardwood trees of North America. It does not harm animals or humans.
This beetle kills healthy trees by burrowing deep and it is attracted to maple trees, specifically ones that produce sap for maple syrup. Adults lay eggs in the tree bark, the larvae and pupa burrow deep into the centre of the tree, and the adults emerge through holes to start the cycle again on a fresh tree.
Be aware if you’re in a regulated area. Don’t remove restricted woody material, including firewood or wood chips. Expect regular visits from the CFIA – they might remove infested trees.
The birch leafminer is included in a group of insects known as sawflies. The fly itself is small (approximately 3 mm long) and black in colour, and can be seen hovering over the tops of birch trees or crawling over its leaves in springtime. The fly will lay eggs within newly flushed leaves, which hatch into larvae a few days later and begin to feed.
The larva causes the damage to the leaves of birch trees. The damage is primarily but can make the tree vulnerable to other insects and diseases.
The bronze birch borer is a native, North American beetle that can cause serious damage to birch trees. The larvae burrow into the tree and starve the tree of nutrients.
Older trees or trees that are in dry areas are more likely to be attacked.
The bronze poplar borer is a flat-headed borer that feeds on poplars and is native to North America. The larvae burrows into the tree and starves the tree of nutrients. This can kill the tree.
The carpenter ant is a social insect and lives in colonies. They nest in wet wood in the cavities of trees. They are not a serious pest but can be an indicator of wood decay.
They are most active at night when they feed on insects, fruit, garbage and the honeydew from aphids.
Carpenter ants only affect decaying wood – not healthy wood. This could mean structural failure of the tree, such as branches falling.
In the tree:
In your home:
You can use boric acid or sodium borate based baits as close to the nest entrance as possible – visit your garden centre for details.
The Eastern tent caterpillar is a native insect that rarely occurs in large enough numbers to cause tree death in Toronto. Their tents are unsightly and disturbing to homeowners.
There are two species of bark beetles that feed and breed on elm trees:
The beetle doesn’t cause permanent damage to a tree but transmits a fungus that does – learn more about Dutch Elm Disease.
The elm leaf beetle is originally from Europe and was first discovered in Ontario in 1945. The beetle doesn’t cause permanent damage to a tree and does not transmit the fungus cause Dutch Elm Disease.
The larvae go to the ground to pupate into adults.
The elm leafminer (Fenusi ulmi) is a European insect that has been known in North America since the late 19th century.
This insect eats the tree’s leaves and makes it difficult for the tree to get enough sunlight.
Attract birds and other creatures that eat these insects by planting a variety of flowers, herbs or shrubs in your garden.
Management program in effect.
The Emerald Ash Borer (EAB) is an introduced insect pest from Asia that attacks and kills all species of ash trees.
It is extremely difficult to tell if your tree is infested and some of the symptoms appear too late or could be considered symptoms of another pest or disease.
You can help spreading this pest by avoiding the planting of ash trees.
If you have an ash tree on your property and it is dead or dying, contact an arborist who is either:
If your tree appears healthy, ask your arborist if your tree would benefit from TreeAzin® injections, which may slow infestations of emerald ash borers down.
For City-owned ash trees on the road allowance in front of your property:
Permit to Injure or Remove a Tree
Fall cankerworm is a native insect that loves to eat leaves. This limits the amount of sunlight a tree receives and can weaken and stress the tree.
Preferred trees:
Install a sticky band around the base of the tree trunk in October. This traps the females and prevents them from laying eggs:
Watch our Sticky Band Trap Installation for Fall Cankerworm Youtube Video.
You can also:
There are several species of plant bugs and leafhoppers that feed on honey locust trees.
Japanese beetles were introduced to North America in 1916. They are a voracious eater of the leaves and fine roots of over 300 different species of plants, grasses and trees.
They cause primarily cosmetic damage but they could weaken the tree and make it more vulnerable to other pests and diseases.
The Japanese Beetle likes to eat the green parts around the veins of a leaf, which gives the leaf a skeletal appearance. The whole tree can look scorched.
Lace bugs are a native North American insect that feeds on a wide range of trees.
They cause primarily cosmetic damage but they could weaken the tree and make it more vulnerable to other pests and diseases.
Don’t use broad-spectrum insecticides since these products can kill insects that eat Lace Bugs.
Management program in effect.
Spongy moth is a defoliating insect that can severely weaken or kill trees. It is a major pest in North America. Learn more about the Spongy Moth (Lymantria Dispar Dispar), what you can do and how the City manages this pest.
A large number of scales, tiny insects, feed on trees by sucking sap from leaves, twigs or stems. They can make trees vulnerable to other pests and diseases.
The eastern subterranean termite was introduced to Toronto in 1938 and has since become established in homes throughout the city.
Termites eat dead parts of trees and don’t attack healthy wood. Termites are hard to detect. The best way to tell if termites are present is to see whether they have built tubes from the ground to the wood they are feeding on.