Invasive Species

Commitment to Inclusion As part of the City of Hamilton’s commitment to diversity and inclusion, the City has replaced the name gypsy moth with its Latin name, Lymantria dispar dispar (LDD) in it’s communications to help educate residents about the invasive pest while remaining sensitive to the negative connotations associated with its common name.

Lymantria Dispar Dispar (LDD Moth) is an invasive forest pest that was introduced accidentally in the United States in 1869. Since then, the LDD moth has expanded its range over much of the eastern United States and Canada. It was first detected in Ontario in 1969 and has quickly spread across southern Ontario. It is now well established throughout southern Ontario and as far north as Sault Ste. Marie.

LDD moth larvae or caterpillars will feed on tree leaves. If the larvae population is high, they can defoliate whole trees and forests in a short amount of time. LDD moth prefer oak trees, but will feed on a variety of hardwood tree species. Under normal circumstances, defoliation caused by LDD moth won’t kill a tree. However, trees can decline to the point of death in some cases when defoliation is coupled with dry hot summers or impacted by other forest pests like Spring or Fall Cankerworm.

Late instar LDD moth larva

Female LDD moth laying eggs

Pupation occurs in a cocoon which can be found on a variety of surfaces including trees, rocks, houses, boats, trailers, fences, picnic tables, and firewood. In 13 to 17 days, the moths emerge. Both sexes have wings, but only the males can fly. The male moth is dark brown to beige, medium-sized, and is a very erratic flyer. The female is mostly white and has a wingspan between 60 to 70 mm. The female lays eggs in masses of 100 to 1000 on tree trunks, branches, houses, fences, etc. as well as under rocks and forest floor debris. The eggs are covered with fine brown hairs from the female’s abdomen. The egg masses will remain all winter and caterpillars will hatch in the spring, from late April to mid-May.

LDD Moth Treatment Area

 To find out if you live in the treatment area, enter an address or intersection into the search box. If your search result appears in the pink highlighted boundary, you are located in the aerial spray zone.

Once the spray program has been completed this year, the Forestry Section will be conducting follow up surveys of the spray area, as well as areas outside of the spray area to verify that the LDD moth population has decreased below threshold levels. If it has been determined that action thresholds have been reached in other areas, the Forestry Section will address it the following year.

Find more LDD Moth data in our Open Data Portal

How The City is controlling LDD moths

Surveying has been underway since the winter of 2016 with the completion of egg mass surveys. In late 2020 / early 2021 The City had surveys completed to determine egg mass counts in areas that had shown high numbers in previous surveys but were not treated and / or areas where residents and staff noticed increased activities in 2020.  Following a review of this information The City will be considering ground spraying using Bacillus thuringiensis ‘kurstaki’ (Btk), as well as banding of City trees in these areas.

Bacillus thuringiensis ‘kurstaki’ (Btk) is a soil-borne bacteria that is applied to the leaves of affected trees while caterpillars are in their early instar stage (immature). Once ingested, the bacterium disrupts the caterpillars’ digestive system with cessation of eating within 24-48 hours. Within days, caterpillars that have ingested Btk will succumb to its effects. Btk has very low residual qualities in the natural environment. Sunlight and fungi deteriorate the bio-pesticide within 1 to 4 days. Because Btk requires an alkaline environment in the gut in order to be effective, it does not have any detrimental effects to humans, birds, or bees. Btk will affect other caterpillar species (known as non-target species). Due to its low residual and the narrow spray window due to larval development, the non-target impact is expected to be low. Conservative and measured application will be undertaken with the goal of reducing the population below the 2,500 egg masses per hectare. This program is not intended to eradicate the pest entirely.

Members of the public are unlikely to experience any symptoms if inadvertently exposed to Btk spray, and no special precautions are necessary or required. However, individuals who have concerns should take reasonable precautions to avoid exposure during a spray program in the same way they would avoid pollen or other airborne materials during days when air quality advisories are issued. They can also reduce exposure by staying indoors with windows and doors shut during the spray period if spraying is taking place in their area, although this is not required by health officials. (Health Canada, 2009)

What homeowners can do to control LDD moths

Homeowners are encouraged to monitor their hardwood trees like oaks, maples, beech and walnut for the presence of larvae.

Frequently Asked Questions

The Emerald Ash Borer is a highly destructive invasive beetle that infests ash trees. It has killed millions of ash trees in North America and poses a major environmental threat to urban and forested areas in Hamilton. It has the potential to destroy Hamilton’s entire Ash tree population by the year 2020.

Identifying Ash Trees

Mountain Ash is not in the same family and is not affected by the Emerald Ash Borer. An Ash tree typically has:

Identifying Signs of Infestation

Emerald Ash Borer larvae feed underneath the bark and block nutrients and water from moving throughout the tree. The tree may be dead within a few years of the initial infestation. Infested ash trees often exhibit the following symptoms:

Removal of infected trees

Who is responsible for removal of infected trees depends on where the tree is located on your property:

Trees in the road allowance

The City will remove an infested ash tree from your property if it is located within the road allowance. If the tree in your front yard is showing signs of being infested with the emerald ash borer, call 905-546- 2489 to have your tree assessed. The City will plant a replacement tree once the infested tree and stump is removed.

Trees on your property

You are responsible for all trees that are not on the City’s road allowance. This includes the treatment, removal and disposal of dying or dead Ash trees. Contact an arborist to discuss your options.

If you elect to have your tree removed, ensure that the materials are not moved outside the CFIA quarantined area. The wood and mulch can be utilized for firewood and landscape use within this area.

Contact the Canadian Food Inspection Agency at 1-866-463-6017 or Phytosanitary Requirements to Prevent the Introduction Into and Spread Within Canada of the Emerald Ash Borer for further information.

City Ash trees

In 2012 City Council approved the plan which included the removal of 10% of Hamilton’s Ash tree population each year for a 10 year period. At the current decline rate, it is anticipated the Ash population may be removed in the next four years. Each Ash tree that is removed is replaced with a new species of tree to help diversify Hamilton's urban forest. More information on the Street Tree Planting Program.

The City has also been using injectable pesticide on healthy Ash trees of significance. These trees are treated annually during periods of heavy infestation then subsequently every two years. Treating all City-owned Ash trees is not economically feasible.

They emerge as adults in October. Adult females are wingless, grayish brown, and about 12 mm long, while the grayish brown, adult male moths have wings with a span of about 30 mm. The adult females climb host trees and shrubs, and mate; each female then lays about 100 eggs on the upper twigs and branches.

Health Effects

These caterpillars can cause significant damage to trees, often causing complete defoliation of a tree. However, a mature, strong tree can survive one to two seasons of complete defoliation. That said, more than three years of defoliation from cankerworm feeding can potentially kill branches.

What homeowners can do to control Cankerworms

Tree banding is an effective method of controlling cankerworms. Adult female cankerworm moths are wingless and need to crawl up the trunks of trees to lay their eggs. Tree bands trap the adult moths as they are crawling up the tree, which usually begins mid-September.  Banding a tree takes just three steps:

1. Wrap a 10-15 cm (4-6 inch) wide strip of fibreglass insulation around the trunk approximately 1.5 m (5 ft) off the ground.
2. Cover the insulation with cling wrap. Be sure to wrap it tightly so that the insulation is pushed into the crevices of the bark and to leave a bit of plastic above and below the insulation. This may take two or three layers of cling wrap.
3. Spread a layer of petroleum jelly or a similar sticky substance on the plastic in a band about 10 cm (4 inches) wide.

Inspect the band regularly and remove any large debris such as leaves. Reapply the sticky material as required. Be sure to remove all tree bands by mid-December. Leaving tree bands on over the summer can cause mold and rot to develop, causing more harm to the tree than the cankerworms.

Giant Hogweed is a non-native invasive plant that poses a serious threat to human health and natural ecosystems. We have found this plant along Spencer Creek and roadways in Dundas. Some plants have been found on private property in Dundas and Flamborough. If you find Giant Hogweed on your property, call 905-546-2489.

How to identify Giant Hogweed

Giant Hogweed looks similar to cow parsnip. It can grow to impressive heights and blossoms.

Typical traits of Giant Hogweed:

• 1 to 5.5 metres in height (3 - 15 feet)
• Large, deeply cut leaves with sharp coarse teeth, reaching widths in excess of 1 m (3 feet)
• Stems are covered in coarse whisker-like hairs, with red-purple spots
• White, umbrella shaped flowers up to 1.2 m (4 feet) across

Health effects

Giant Hogweed’s leaves and stem produce a watery sap containing a chemical, which makes human skin highly sensitive to the sun and other sources of ultraviolet light. Touching the plant or brushing against it is enough to cause serious injury. Exposed to sunlight, the sap causes painful blistering within a few hours of contact. The healing process can be slow, and your skin may remain sensitive to sunlight for the rest of your life. Blindness may occur if the sap gets into your eye.

If any sap touches your skin:

• wash the affected area immediately with soap and water
• keep the affected area out of the sun
• see your doctor if you have a reaction

Removing Giant Hogweed from your property

For your own safety, we encourage you to contact a licensed weed exterminator to remove Giant Hogweed from your property. 

Do not compost Giant Hogweed. Do not put Giant Hogweed out as leaf and yard waste or in your green bin. It is accepted in the garbage if sealed in a bag (no dirt).

Report giant hogweed on City property

The City has received approval from the Ontario Ministry of the Environment to eradicate Giant Hogweed on road allowances and City maintained trails using a spray herbicide. Red signs warning of herbicide use are posted when used for Giant Hogweed.

If you find Giant Hogweed in parks or on trails, call 905-546-2489.

Hemlock woolly adelgid is an aphid-like insect that attacks and kills hemlock trees. Its egg sacs, which look like cotton balls or clumps of snow, can be found at the base of needles.

The environmentally safest chemical control methods for treating individual trees are nontoxic insecticidal soap and horticultural oil. These are sprayed on the foliage and smother the insects as they dry. Most trees need to be treated on a yearly basis.

What homeowners can do to control Hemlock Woolly adelgid

You can apply horticultural soaps and oils 2-4 times per year in an effort to control the population to a point where the insect is not harming the tree. However, even with control there will still be active scale populations on the tree that will still cause sap to drip, and attract wasps, etc. The insect is protected by a hard shell that pesticides will not penetrate. The only time to spray is in the spring or late summer/fall when the new crawlers (young nymphs) are mobile. When the insect cannot be treated, the only options are to prune the tree to reduce the problem, or prune away from a used area such as a deck.