Invasive Species

What are Invasive Species?

Plants, animals and micro-organisms that have been introduced (accidentally or deliberately) to non-native areas.
They have negative impacts on the natural biodiversity/environment, economy and/or society, which can include human health.

Spongy Moth (Lymantria dispar dispar/Gypsy Moth)

Spongy Moths (Lymantria dispar dispar), formally known as Gypsy Moths, are an invasive insect that can cause moderate to severe defoliation of certain types of trees. The caterpillar of this insect feeds on all species of oak, but also feeds on poplar, birch, willow, maple, beech, and cherry. If faced with a shortage of deciduous leaves, they will feed on conifers (hemlock, pine and spruce) and ornamental shrubs. Healthy trees can usually withstand losing their leaves for a few years, but several years of defoliation can weaken and even kill vulnerable trees.

The spongy moth was introduced into Massachusetts in 1869 in a failed attempt to create a North American silk industry. The caterpillar or larva stage of the spongy moth eats the leaves of trees and this causes the trees to be more vulnerable to disease and attack from other insects. There are steps we can all take to minimize their impact at all stages of their growth and life cycle.

What residents can do to protect their trees

The community is in an area which is experiencing a spongy moth outbreak, according to the Ministry of Natural Resources and Forestry. We are optimistic that naturally occurring controls will be effective in mitigating the effects as they have done in previous years.

Most of the trees in Halton Hills are on private land. Property owners are encouraged to help reduce the impact on the community’s tree canopy by reducing spongy moths on their property. If you’re worried about the trees on your property you can try the methods listed below or consult a local tree service company. Control methods are linked to the spongy moth’s stage of development.

Watch the free information webinar on spongy moths hosted by the Toronto and Region Conservation Authority in partnership with Credit Valley Conservation. Viewers will learn about the spongy moth life cycle, how to identify them, and what actions you can take to minimize their impact to trees.

Watch the webinar

August to early May:

Remove and destroy egg masses

During this time spongy moth eggs are present on tree trunks, branches, building structures, and objects around the home.
By destroying egg masses, which can contain 300 eggs, you will significantly reduce the number of caterpillars that emerge in the spring.
Place collected egg masses in soapy water for a few days. Afterwards, discard them in the garbage.
With a dull knife, scrape off egg masses. If they fall to the ground, crush them with your shoe.
It is easy to vacuum egg masses off trees, buildings, and other objects with a portable or a household vacuum cleaner.

May to July:

Hand picking caterpillars

Scrape off caterpillars into water/soap mixture, leave for a few days and then dispose in the garbage. Do not scrape caterpillars onto the ground. If caterpillars fall to the ground, destroy them immediately.
Wear gloves since caterpillar hairs can cause skin irritation or allergies.

June to August:

Place burlap bands

Download and print our Burlap Band Trap Instructions flyer.

Place burlap (cloth) bands on tree trunks to trap and destroy caterpillars.
Wrap burlap that is approximately one metre wide around the tree trunk. Tie it at the middle with a rope, and fold the burlap over. This way caterpillars will congregate under the burlap.
Caterpillars that emerge from under the burlap late in the afternoon should be destroyed before they crawl back to the canopy to feed.
Check for caterpillars under the burlap fold in late afternoon. Shake the caterpillars into a bucket of soapy water to destroy them and prevent them from crawling back up to the canopy to feed. Place a lid over the opening and let sit for a couple of days.
Wear gloves since caterpillar hairs can cause skin irritation or allergies.

Burlap wrapped around tree trunks

July to end of August:

Place pheromone moth traps

Use adult moth traps to catch male spongy moths (available for purchase from most garden centres or online). Traps should be hung from a tree or placed on a stand approximately 4 to 5 feet from the ground.
Traps should be disposed of in the garbage.

What is the Town doing?

Healthy trees can usually withstand losing their leaves for a few years. In the past the Town has allowed nature to take its course and spongy moth infestations have naturally collapsed without notable impact to the trees. With the spongy moth population having increased in recent years, the Town has received a number of inquiries regarding control of the infestation. Staff have developed the following response plan for 2022:

Enhanced public communication and education. The Town is partnering with CVC and CH on virtual public information workshops that will focus on invasive pests (including the spongy moth) within the Halton Hills Public Library Lecture Series.
Deployment of moth traps on Town trees, as in prior years, to minimize reproduction.
Pilot limited ground spraying of bio-pesticide on small to medium feature trees within Town parks and/or facility grounds, as appropriate.
Pilot the offering of free burlap kits (i.e., length of burlap, string, instruction sheet) to residents for use on private and/or Town trees.
Perform a survey of actual defoliation in 2022 to better understand any potential need for increased response actions in 2023 or beyond (i.e. to track tree stress from potential repeated defoliations).
Perform another egg mass survey in fall 2022 to forecast potential defoliation in 2023 (if required with no significant spongy moth population collapse in 2022).

Additional Resources

Giant Hogweed

What is it?

An invasive plant.
The sap of Giant Hogweed can negatively affect human health.
Can be found along roadsides, vacant lots and stream banks.

Symptoms caused by Giant Hogweed sap

Serious skin inflammation (photodermatitis).
The skin to be highly sensitive to UV rays due to a chemical called furanocoumarins.
Skin blisters, redness, scarring, and other discolouration that can last for years.
Temporary or permanent blindness if sap enters the eyes.
Reactions that can occur for up to 48 hours after contact.
Heat and moisture (sweat) can enhance the reaction.

What does it look like?

Height

1 to 4 metres (3 to 14 feet)

Flower

Large white clusters of small flowers
Umbrella shaped
30 to 60 cm in diameter (1 to 2 feet)

Leaves

Up to 1 metre (3 feet) in diameter
Sharp coarse teeth
Compound leaves deeply divided into lobed toothed leaflets
Produces watery sap

Stem

Rough and bumpy
Course white hairs emerging from bumps
Hollow
Purple/red splotches

How can I be exposed to the sap of Giant Hogweed?

Touching or brushing up against the plant.
Touching clothing or pets that have come into contact with the plant.
The sap can become airborne by pulling, cutting or mowing giant hogweed. This can cause sap to get in the eyes.

What do I do if I accidentally come into contact with Giant Hogweed?

Wash the affected area immediately with soap and water.
Keep the affected area out of the sun for at least 48 hours.
Seek medical attention.

What do we do?

Inspect locations
Control and treat hogweed with pesticides as permitted by Community Standards By-law 2008-0138
If you find giant hogweed on municipal property please contact Public Works at 905-873-2600, ext. 2603.

If you suspect Giant Hogweed is on your property

DO NOT TOUCH! Keep children and pets away from the area.
You are encouraged to contact a licensed weed exterminator. They can be found under “Weed Control Services” in the Yellow Pages. If you choose to remove giant hogweed yourself, USE EXTREME CARE. Information on Giant Hogweed removal methods and how to report a sighting can be found at Ontario Invasive Plant Council.
DO NOT compost the plants.
DO NOT place out for curbside collection either as Leaf & Yard Waste, Green Cart or waste material.
Giant hogweed must be taken to the Halton Waste Management Site for safe disposal.
Monitor the area for future growth.
Community Standards By-law 2008-0138 Part 3, Section 8 Nuisance Weeds states "Property Owners are required to destroy and remove all nuisance weeds and weed seeds on their land."

Additional Resources

Emerald Ash Borer (Agrilus planipennis)

What is it?

Invasive and highly destructive insect.
Attacks and kills all Ash trees native to North America.
Brought to Canada unintentionally through wooden packing crates from Asia in the early 1990s.
Identified as an invasive alien species by the Canadian Food Inspection Agency (CFIA) for Halton in 2009.
Has the potential to eliminate ALL of our Ash trees (5 to 10% of our urban forest*).
A large section of Ontario and Quebec is under quarantine.
Movement of ash wood products outside of the regulated area is prohibited (Map of Areas Regulated for the Emerald Ash Borer).

*An urban forest refers to all of the collective varieties of trees that we have growing on our streets

Signs of Emerald Ash Borer

Bark damage – vertical cracks in the bark
Discolouration or yellowing of leaves
D-shaped holes on bark and branches
Crown dieback - loss of leaves in the tree canopy
Shoots growing from trunk and branches of the tree
Increased presence of woodpeckers feeding

Municipal Ash Tree Management

The remaining street Ash trees can be considered “standing dead” as they will all succumb to the EAB over the next few years and the trees will be removed and replaced as time and budget allows. See the "Emerald Ash Borer Management Strategy" Council Report 2012-0034 from October 15, 2012, for more information.

If you suspect EAB on a tree located on Town property, please contact Public Works at 905-873-2600 Ext. 2603 to request service. If you suspect a tree on your property is infested, or are interested in treating a tree on your property, please call a certified arborist for more information.

Additional Resources

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