Tree Pests and Diseases

There are numerous tree pests and diseases in Wellington County. Information is provided a few of these that pose the biggest threat to tree/forest health and biodiversity.

Buy Local, Burn Local

Emerald Ash Borer

Spongy Moth

Tree Pests & Threats

Dying ash tree surrounded by healthy trees and reaching up towards a bright sky.

Don't Move Firewood - buy local, burn local.

The spread of invasive pests/diseases is commonly assisted by people unknowingly moving firewood with insects, insect eggs and/or fungal spores that are very difficult to see. Invasive tree pests and diseases pose a substantial risk to the environment and economy of Wellington County. A best practice is to burn firewood where you buy it. Be aware of the harms of moving firewood and movement restrictions that may be in place.

Learn more about the Hazards of Moving Firewood

Emerald Ash Borer

A few years ago the Canadian Food Inspection Agency confirmed the presence of Emerald Ash Borer (EAB) in the Township of Puslinch. The infestation has continued to spread and intensify across our County. Experts have estimated that as many as 98% to 99% of the Ash trees will be killed over the next decade as a result.

It is possible to protect trees with an inoculation. However, this is costly and must be repeated after a certain number of years. It is likely that this treatment will only be used on large specimens which have heritage values.

The most immediate problem is in our urban areas. Once dead, Ash trees become unstable quickly, creating a hazard. The trees will need to be removed, which will be costly over a number of years. Local municipalities will need to develop a plan to deal with the problem, and budget for this expense. Currently, there are no provincial or federal programmes to offset costs.

In our rural forests, up to 30% of the trees may be Ash in places. Their loss will have significant impact on our forest lands. Landowners are encouraged to manage the decline, marketing the trees while still of value. Replacement trees of the appropriate species should be replanted in the remaining forest. Wellington County's Green Legacy Programme will be able to assist replanting where needed with nursery stock in rural areas and larger potted stock in urban areas.

Additional Resources

Spongy Moth (Lymantria dispar dispar)

The Lymantria dispar dispar (LDD) Moth, which is commonly referred to as the Spongy Moth or European Gypsy Moth, is a non-native insect that was introduced to Canada in 1969.

The impacts of defoliation from the LDD Moth can vary from minor to severe and it is generally understood that a healthy tree can withstand some defoliation. However, the defoliation of the trees can make them more vulnerable to disease, other insects, and environmental stressors. A single moth caterpillar can eat an average of one square meter of leaves.

The tree types most commonly impacted by the LDD Moth include oak, birch, poplar, willow, and maple trees. The Moth may also defoliate softwood trees such as white pine and blue spruce.

Frequently Asked Questions

What does the LDD Moth look like?

Сaterpillar nest of a gypsy moth (Lymantria dispar) on a tree branch.

There are different life stages of the LDD Moth and in each stage the appearance changes significantly. Unique characteristics assist with identification:

Egg masses – tan coloured, about 4 cm long, and can be found on tree trunks, furniture, buildings etc.
Young caterpillars - are black or brown and about 0.6 cm (0.24 inches) in length.
Older caterpillars - develop bumps along their backs with coarse black hairs and in the later stage, the caterpillar is charcoal grey with a double row of five blue and six red dots on its back. Mature caterpillars can be as long as 6.35 cm (2.5 inches).
Adult moth (male) - the male LDD Moths are greyish brown in colour and can fly.
Adult moth (female) - are larger than the males and are whitish in colour with dark markings and/or darker zigzag marks. The female cannot fly and dies shortly after laying eggs.

More images and further information can be found on the Invasive Species Centre website.

What is the life cycle of the LDD Moth?

Management on private property - What can you do?

The Province of Ontario has released a diagram that identifies the LDD Moth’s lifecycle and options for controls during each stage.

Life Cycle of LDD Moth

Looking for professional advice? Contact a tree specialist or an accredited arborist to develop a plan that suits your needs.

Find an arborist

A common and effective pesticide used to manage an LDD Moth infestation is BTK (bacillus thuringiensis kurstaki). Before considering the use of this product, consult a reputable contractor. Pesticides are most effective at the caterpillar stage (Mid-April to Mid-May).

Please use caution. The LDD Moth has long hairs that can cause skin irritation or allergic reactions for some people. For safety, use gloves while handling caterpillars.

How can I safely remove egg masses?

Egg masses should be removed and destroyed at the beginning of each year, before the spring. Below are step-by-step instructions on how to manually remove egg masses:

Place your catchment container below the egg mass.
Use your scraper tool to remove the egg mass from the surface. Ensure that all eggs are scraped. Try not to leave any residual eggs in bark ridges or crevices.
Empty the contents of your catchment container or bag into a bucket of soapy water.
Leave the eggs sitting in the bucket for a couple of days, then dispose of the contents.

How do I use a burlap banding kit?

Burlap banding kits are effective at the caterpillar stage of the Moth's life. Below are step-by-step instructions on how to install a burlap banding kit:

Wrap and secure a piece of burlap cloth around the stem/trunk of your tree.
Tie twine or rope around the centre or slightly below the centre of the burlap.
Drape the burlap cloth over the twine or rope so there is an overhang where the caterpillars can crawl underneath to seek shelter during the day.
Check the trap by lifting the overhanging burlap cloth every afternoon and collect any hiding caterpillars.
Put them into a bucket of soapy water for a couple of days to destroy them.

The use of protective gloves is recommended.

How-to video - burlap against LDD Moth.

Does the LDD Moth have any natural enemies?

Additional Resources

Potential Tree Pests and Disease Threats

The following tree pests and diseases have not been found in Wellington County, but they have been confirmed in nearby municipalities or near the Ontario border.

Asian longhorn beetle (Anoplophora glabripennis) sits on a green leaf.

Asian Long-Horned Beetle

Asian Long-horned Beetle (ALHB) is a large shiny black beetle with white dots on its back that can infest maple, birch, poplar, and willow trees. In 2013 an ALHB infestation was confirmed near Pearson International Airport.

Tree with bark falling off and an black dot of fungus in the centre of it.

Oak Wilt

An invasive vascular disease caused by the fungus Bretziella fagacearum threatening oak trees in Canada. The fungus grows on the outer sap wood of oak trees, restricting the flow of water and nutrients and can kill a tree within a single growing season.

Hemlock Woolly Adelgid

A tiny, invasive aphid like insect that attaches to the branch and feeds at the base of needles extracting nutrients and sap. Once attacked by HWA hemlock trees do not recover and trees usually die within 4 to 15 years of infestation.

Not sure what type of trees you have?

Check out Forests Ontario to find out.