Tree Health

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 1869 to the United States. Since then, the LDD moth has expanded its range over much of the eastern United States and into Canada. It was first detected in Ontario in 1969 and has since 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 feed on tree leaves. If the larvae population is high, they can defoliate entire trees and forests in a short period 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 when defoliation occurs during dry, hot summers or the trees are already impacted by other forest pests like Spring or Fall Cankerworm.

Late instar LDD moth larva

Female LDD moth laying eggs

What You Can Do

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

What the City is Doing

The City surveys and monitors populations of LDD moth and consults with government agencies and local municipalities to determine appropriate treatment programs that is dependent on LDD moth population levels. 

The City’s LDD moth control program has been in place since 2008 and the program goal is to reduce LDD moth population level to below 2,500 egg masses per hectare. This program is not intended to eradicate LDD moth entirely.

Treatment options that have been previously undertaken include burlapping trees, aerial spraying, targeted ground spraying and egg mass collection. The product used in the spray program is an organic bio-pesticide that targets LDD moth and other caterpillars, and does not affect humans, pets, other animals, or bees. To learn more about the product used, see the Health Canada Btk Fact Sheet.

Public notice is always provided ahead of any treatment program being initiated.

The Emerald Ash Borer is a highly destructive invasive beetle that infests and kills ash trees. Ash trees are native to Ontario and were once popular trees found on City streets, woodlots and forests. Since first arriving in Canada in 2002, EAB has killed millions of ash trees in North America and has killed most of Hamilton’s ash tree population.

What the City is Doing

EAB was first detected in Hamilton in 2009 on the Hamilton Mountain.  In 2012, the City launched a 10-year proactive management strategy to manage publicly owned ash trees, infested with the EAB, within the right of way in the urban boundary and in City parks and cemeteries.

Over the 10-year period, EAB damage to the ash tree population was significant City-wide, with most ash trees dying or declining to the point they required removal to mitigate risks to public health and safety. 

What You Can Do

If you have an Ash tree on your property that you think is infested with EAB, the first step is determining if that Ash tree is on private or public property (link to Tree Ownership and responsibilities webpage).

If the tree is on public property, call 905-546- 2489 to have your tree assessed by the City.  If the City determines that the tree requires removal, the City will remove the tree and stump and will plant a replacement tree.

If the tree is on Private Property, it is your responsibility to maintain the tree, including removal if you suspect that the tree is infested. If you are unsure, you can hire a Tree Service Company to inspect and remove the tree, if required.

The young larvae of Fall Cankerworms feed on leaves of host trees and can defoliate the entire tree.  When cankerworm populations are large, larvae in search of food can drop silken threads and become a nuisance around homes.

While alarming, 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.

Preferred host trees include Manitoba Maples, Elm, and various fruit trees, however Fall Cankerworm can also attached Basswood, Burr Oak, Aspen and White Birch.

What You Can Do

Tree banding is an effective method of controlling Fall 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.   

You should band your trees from late March to mid-May and again from early September to mid-November to catch the cankerworms moths at both the times they are emerging from the soil. 

It is important to band all trees in an area or else cankerworm larvae could move from unbanded trees to banded trees. Please do not leave bands up longer than recommended as it can do more harm than good to the tree.

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.

What the City is Doing

The City, in conjunction with the Canadian Food Inspection Agency (CFIA) and other agencies, monitors Fall Cankerworm populations, and distributes and provides relevant information for suspected cases.

Hemlock Woolly Adelgid (HWA) is a destructive aphid-like pest that attacks Eastern Hemlock, an ecologically significant tree species in eastern Canada. It feeds on the base of the needles, causing needle drop and tree mortality in as few as 4 years. 

HWA can be identified by its egg sacs, which look like cotton balls or clumps of snow, and can be found at the base of needles.

What You Can Do

• Avoid placing bird feeders near hemlock trees – birds can accidentally transport HWA to new locations.
• Don’t move firewood! Human movement of wood products increases the spread of HWA. 
• In the spring, keep an eye out for signs, such as woolly egg masses, on your hemlock tree and report any potential sightings.

Photo credit: Natural Resource Canada; CFIA

If you believe you have identified HWA on your property contact your local Canadian Food Inspection Agency (CFIA) Office at 905-572-2201 to have an official identification. You can also report a potential invasive pest on the CFIA website.

If you have identified a potential HWA population on a street tree or a tree within a City of Hamilton Park or Cemetery, please call the City of Hamilton Contact Center at 905-546-2489.

What the City is Doing

The City, in conjunction with the Canadian Food Inspection Agency and other agencies, monitors and reports on suspected HWA sightings. 

Spotted Lanternfly (SLF) is an invasive insect that kills plants and trees by sucking the sap from leaves and stems. SLF feeds on over 70 species of trees and plants, including cultivated grapes and fruit crops, and poses a threat to Canadian wine, fruit, and forest industries. 

SLF has not yet been detected in Canada, but was identified in Buffalo, New York near the Canadian border in September 2022.

What You Can Do

Review the Fact Sheet to learn how to identify SLF.

If you believe you have found SLF or its egg masses, seal them in a container and immediately notify the local Canadian Food Inspection Agency (CFIA) Office at 905-572-2201 to have an official identification. You can also report a potential invasive pest on the CFIA website. 

Photo credit: CFIA

If you have identified a potential Spotted Lanternfly on a street tree or a tree within a City of Hamilton Park or Cemetery, please call the City of Hamilton Contact Center at 905-546-2489.

What the City is Doing

The City, in conjunction with the Canadian Food Inspection Agency and other agencies, monitors and reports on suspected SLF sightings.

Oak wilt is a vascular disease of oak trees caused by a fungus that grows on the sapwood of oak trees that restricts the flow of water and nutrients. Some oak trees are more vulnerable and can die within a year of infection, and in some severe cases, mortality can occur within 2-6 weeks following infection.

In June 2023, the presence of oak wilt was confirmed by the Canadian Food Inspection Agency in Niagara Falls, Ontario. This is the first known case of this vascular disease of oak trees in Canada.

Signs and symptoms

• Sudden leaf wilting.
• Premature leaf drop, beginning at the top of the crown.
• Brown veins in the leaves mixed with normal green tissue. 
• Vertical cracking in bark.
• Grey or tan mats of fungus under the bark of an infected tree.

Photo credits: CFIA, Arborjet, and USDA Forest Service

What You Can Do

Oaks that belong to the group of red oaks (pin oak, black oak, northern red oak) are more susceptible than white oaks (white oak, bur oak, swamp white oak). There is no way to save an infected oak tree; the only way to deal with oak wilt is prevention.

• Don’t Move Firewood! Buy where you burn it or buy certified heat-treated firewood. Check with parks or campgrounds before you go for rules about firewood.
• Since the fungus enters the tree through wounds, refrain from cutting, pruning, harvesting or injuring oak trees on your property between March until October. Be careful maneuvering around oak trees with your lawnmower and other power tools.
• Learn to identify oak trees on your property and become familiar with signs and symptoms.

• Review the Fact Sheet to learn how to identify Oak Wilt

If you believe you have identified oak wilt on your property contact your local Canadian Food Inspection Agency (CFIA) Office at 905-572-2201 or email [email protected] to have an official identification. You can also report a potential invasive pest on the CFIA website.

If you have potentially identified oak wilt on a street tree or a tree within a City of Hamilton Park or Cemetery, please call the City of Hamilton Contact Center at 905-546-2489.

What the City is Doing

The City, in conjunction with the Canadian Food Inspection Agency and other agencies, monitors and reports on suspected Oak Wilt sightings.

Don’t worry, it is a very common thing to get yellow or black spots on your maple tree leaves.  This is caused by a fungal disease, also known as Tar Spot. Tar Spot makes trees look unpleasant, but is rarely harmful enough to affect the health of trees, through heavy infections can cause early leaf drop.

What You Can Do

A variety of factors contribute to the spread and recurrence of this fungal infection. Some factors, such as weather, are not able to be controlled. However, there are some ways in which you can help to prevent infection. 

Proper garden and yard sanitation will help reduce the spread of tar spot. 

• In the fall, remove all infected leaves by bagging or composting them to eliminate the closest source of tar spot spores. If you leave the fallen leaves on the ground until spring, the spores on them will likely reinfect the new foliage and start the cycle again.
• Eliminate standing water around infected trees as trees that get the fungal disease year after year may be struggling with excessive moisture. 
• Treat young maples trees. If you’re planting a young maple in an area prone to the fungal disease,  you can apply a fungicide such as:
  •  Safer Defender Garden Fungicide 1L Ready-to-Use or Safer 3-in-1 Garden Spray 1L Ready-to-Use, at bud break and twice again in seven-to-fourteen-day intervals.
  • Once your tree is well-established and too tall to easily spray, it should be able to fend for itself.