Pests and Disease
Aphids | Ash Leaf Cone Roller | Black Knot | Bronze Leaf Disease | Poplar Borer | Yellowheaded Spruce Sawfly
Aphids
Where do they live?
They live in many tree and plant species.
What are the signs?
You will see honeydew falling from trees, curled and deformed leaves and shoots and the presence of ants. There will be darkening of the bark on younger elms caused by sooty mould growing in the honeydew. Honeydew is excreted by sap sucking insects such as aphids.
A bugs life?
Aphids hatch in early spring and feed on the sap plants. They all hatch as females and are able to reproduce asexually, giving birth to live young. Only when there is an over population or plant host death do aphids grow wings so they can fly to another location. Later in the year, both female and male aphids are produced and they mate and produce the eggs that will hatch in the spring.
How does this effect trees?
Mostly aesthetic and annoyance.
What can you do?
Spray aphids of a plant with a powerful stream of water. There are many natural predators of aphids including ladybugs.
Ash Leaf Cone Roller
Where do they live?
Green, Manchurian and Black Ash. Green, Manchurian and Black Ash.
What are the signs?
Leaves rolled into cones.
A bugs life
This insect starts off as a leaf miner, actually living within a leaf. Later it emerges from the leaf and cocoons in the rolled up leaf. Its adult form is a small moth. There are naturally occurring predators of this caterpillar including a non stinging wasp, birds and more.
How does this effect trees?
The rolling of the leaf is more of an aesthetic problem as there doesnÕt seem to be any major detrimental effects to the tree.
What can you do?
Let nature take its course. This insect does not damage the leaf enough for it not to be able to perform photosynthesis.
More on the Ash leaf cone roller
Black Knot
Where do they live?
Black Knot is a fungus that grows on Cherry Trees (e.g. Pin, Schubert, Chokecherry and Maydays) and on other Prunus species. Black Knot is a fungus that grows on Cherry Trees (e.g. Pin, Schubert, Chokecherry and Maydays) and on other Prunus species.
What are the signs?
Black Knot appears as a brown swelling on a branch, twig or even the trunk. It grows larger and becomes a black knot
How does this effect trees?
Black Knot can weakening and will eventually kill a tree if left unchecked. A tree left with knots on it will infect other trees as the fungus releases spores into the air.
What can you do?
In the fall or winter, prune out knots 15-20 cm below the knot when possible. Check for new knots every winter and remove. Dispose of infected branches by burning, throwing in your green cart or taking it to the Streambank Avenue Recycling Centre. Do not put in your backyard composter.
Bronze Leaf Disease
What trees does this disease affect?
Swedish Columnar Aspen, tower poplar, poplar hybrid clones
What is the disease cycle?
Spores are released from mature preithecia (spore producing structures that develop on overwintered leaves). The spores are then spread during the spring to infect leaves on the same tree and other nearby trees. The disease will develop over the summer and infections will spread internally to other parts of the trees. Symptoms typically appear in later summer (early-mid August) or early fall (September). You will begin to see individual branches or a few leaves suddenly show symptoms.
What conditions help spread the disease?
Rain and moderate to warm temperatures (18 degrees Celsius) lead to spore dispersal.
What are the symptoms?
Leaf tissues turn orange-brown to reddish-brown, starting from the edges of the leaf, moving inward towards the base of the leaf. Leaf veins and petiole remain a bright green colour. All leaves on a branch may be affected. Discolouration deepens to a bronzy, reddish-brown colour as the season progresses.
Infected leaves will often remain attached to the tree over the course of the winter (they do not fall off). Branches may dieback as the disease progresses systemically. Leaves that overwinter may have a pebbly surface texture (like the surface of a curling rink), reflecting the development of spore-producing structures (perithecia).
What can you do?
Prune affected areas of the tree. Cut off leaves and branches, place in a sealed garbage bag and dispose of in your black waste cart or take to the landfill. The sealed plastic bag will help prevent spores from spreading the disease.
Please DO NOT do the following:
- bring infected brush to the Streambank Avenue Recycling Centre
- place in your backyard composter
- burn or place in your green cart
- chip or use as mulch
- Assessing trees listed in the Tree Inventory for signs on damage
- Pruning affected trees and removing severely infected trees
- Bagging the trees/branches/leaves and disposing of them in the landfill
- Educating residents about the disease and how to care for their affected tree
Poplar Borer
Where do they live?
Aspens, Cottonwoods, Willow and Poplars. Often found in columnar poplar, around the edge of native aspen stands and lone trees.
What are the signs?
You will see large bore holes with sawdust (shredded wood) coming out of the holes and piled at the base of the trunk. Sap leaks down and stains the bark brown attracting other insects.
A bugs life
Larvae burrow into trees where they reside for 2-5 years before emerging as adults. Many larvae are killed by woodpeckers, nematodes and other natural predators and over 60 per cent never make it to maturity.
How does this effect trees?
Trees can be weakened structurally when several larva are present.
What can you do?
If a tree is infested, remove it and destroy the wood by chipping, burning or take it to a recycling centre. Do not store for firewood.
www.talkaboutwildlife.ca
More on the poplar borer
Yellowheaded Spruce Sawfly
Where do they live?
In a variety of spruce species.
What are the signs?
You will see the larvae itself and defoliation of the ends of branches.
A bugs life
The Sawfly pupates over winter in the soil beneath the tree. Adults are a clear winged stingless wasp and emerge in spring/summer and lay eggs on new growth. Larva feed on needles, both new and old working from the outside of the tree inward. There are a lot of natural predators including birds and ground beetles that will eat the pupating Sawfly.
How does this effect trees?
Sawfly larvae can defoliate a tree if it is heavily infested. Bare branches and defoliation affect the aesthetics of a tree. Repeated defoliation is where the danger to the tree lies.
What can you do?
One can remove by hand or spray larvae off with high-pressure water. Disturbing the ground under the tree may disrupt pupation.
For more information, visit Natural Resources Canada.
Additional links to Natural Resources CanadaLast updated: Friday, September 16, 2011
Page ID: 7540