Tree Maintenance

Emerald Ash Borer

Emerald Ash Borer perched on a persons fingerThe Emerald Ash Borer (EAB) is an introduced insect pest from Asia that attacks and kills all species of ash (genus: Fraxinus) trees.  This invasive pest devastated ash trees in southern Ontario and parts of the United States since its discovery in Detroit, Michigan in 2002.

In 2007, The Canadian Food Inspection Agency (CFIA) confirmed the presence of the EAB in Toronto in the vicinity of Sheppard Avenue East and Highway 404. 

As a result of the EAB infestation in southern Ontario, the  Canadian Food Inspection Agency (CFIA) has instituted a quarantine zone through a Ministerial Order which covers most of southern Ontario: CFIA Link: EAB Quarantine Zone. The Ministerial Order identifies prohibitions and restrictions of movement on nursery stock, trees, leaves, logs, lumber, wood, wood chips and bark chips from all ash species and for firewood of all species. This is necessary to prevent the spread of the EAB into un-infested areas in other parts of Ontario and Canada.

What is the Emerald Ash Borer (EAB)?

EAB is an introduced insect pest from Asia that attacks and kills all species of true ash trees (genus: Fraxinus) by feeding beneath the bark and disrupting the flow of water and nutrients within the tree.

How much damage can the EAB cause to trees?

Tree mortality will result if a tree has been infested with EAB. Mortality may occur in as short a period as one year, however, death normally occurs within 2-3 years of a tree becoming infested.

How can I tell if an ash tree is infested by EAB?

Unfortunately, this is extremely difficult. Without cutting the tree down and skinning off most of the bark, it can be difficult to determine whether a tree is infested. A lot of the symptoms associated with EAB, such as shoots (suckers), cracking bark, D-shaped holes and thinning crowns only become evident after two or more years of infestation. One or more of these symptoms may appear even without the presence of EAB.

For more information, see Canadian Forest Service "A Visual Guide to Detecting Emerald Ash Borer Damage" (PDF)

What should I do if I have a privately-owned ash tree on my property?

Property owners are responsible for taking care of privately-owned trees. The City recommends you monitor the condition of your tree, looking for signs of infestation. Most ash trees in Toronto are expected to deteriorate considerably and die over the next several years. When you see signs that your ash tree is dead or dying, you should contact a professional tree care company (you can find these in the Yellow Pages and other business directories). You should choose an arborist certified with the International Society of Arboriculture (ISA) or registered with the American Society of Consulting Arborists (ASCA). Make sure to ask if there is a fee for inspection and quotes; some companies provide these services free of charge.

If your ash tree appears healthy, you may consider asking your arborist to assess whether the tree may benefit from TreeAzin injections (see below). In some cases, TreeAzin may be able to slow the EAB infestation within a single tree.

Private property owners are strongly encouraged to consider planting new trees before or after ash tree removal. Healthy trees can increase property value, help cool your home and clean the air, along with other environmental, economic and aesthetic benefits.

The City of Toronto's recent tree canopy study estimates that there are 860,000 ash trees in total on public and private lands. Inspections and systematic surveys in 2008-2011 have confirmed the EAB infestation throughout most parts of the City.

Where in Toronto was EAB found?

In 2007 the Canadian Food Inspection Agency (CFIA) first confirmed the presence of the EAB in Toronto, in the vicinity of Sheppard Avenue East and Highway 404. Systematic surveys conducted in 2009, 2010 and 2011 have confirmed EAB infestation throughout the east, north and west parts of the City. Currently there is no evidence of EAB infestation in the downtown core. Urban Forestry is continuing the survey and will provide updates on new areas of infestation.

How severe will the infestation be?

Thus far, infestations elsewhere in North America have increased and spread despite significant control measures attempted. Once established, EAB has proven impossible to control. Movement of infested wood, wood products or nursery stock has likely resulted in the spread of this insect to Toronto. Once established, adult EAB can disperse to distances of several kilometres by flight. Emerald ash borer is well established in Toronto; spread of the infestation and ash mortality is expected to expand City wide.

How many trees could be affected by EAB?

All ash trees in Toronto are at risk from this infestation. It is estimated that Toronto has an ash street tree population of 32,400 trees. The recent canopy study estimates that there are 860,000 ash trees in total on public and private lands. The initial areas of infestation that are detected in 2007 are likely to lose most ash trees by 2015. EAB will spread to the rest of Toronto, killing most ash by about 2015 - 2017.

  • Systematic survey of infestation and ash mortality
  • Insecticide injection of 13,000 selected ash trees
  • Removal of dead and dying ash trees
  • Tree replacement and proactive planting
  • Communication and public outreach
  • Co-operation with public and private sector, research and development and other stakeholders.

To learn more about the experience of the United States in dealing with EAB and what Urban Forestry is doing to educate residents of Toronto about this pest, read the staff report entitled Educating Homeowners about the Emerald Ash Borer and the U.S. Experience in the Protection of Ash Trees.

What is the City of Toronto doing to manage the impact of EAB on the urban forest?

EAB is well established throughout most of southern Ontario, including Toronto.  At this stage of the infestation, control of the spread is no longer feasible.  Urban Forestry has implemented a comprehensive plan (EAB Staff Report - PDF) to manage and mitigate the impact of the Emerald Ash Borer on Toronto's urban forest in future years.  Unlike ther invasive species like the Asian Long-Horned Beetle, eradication of the EAB is not possible.   Implementation of the management plan is intended to achieve the following key objectives:

  1. Removal of dead/dying city owned ash trees to mitigate public hazards as a key priority.
  2. Implementation of an aggressive pesticide injection program using the bioinsecticide TreeAzinTM.  Approximately 13,000 suitable ash trees have been selected for treatment over a 2-year cycle.
  3. Intensive tree planting program has been put into effect to mitigate the loss of tree canopy from the removal of dead/dying ash trees throughout the City. 
  4. Communication with the public in order to raise awareness of the EAB, prepare residents for the removal of privately-owned trees and encourage replanting of trees on private lands.
  5. Cooperation with different levels of government, public and private sectors, researchers and other stakeholders in order to aid in the development of new research and controls of EAB.


Has the City already started planting new trees species in areas affected by the EAB?

Yes, the City has been proactively planning and planting trees in areas where ash trees form a large part of the existing tree population. This includes tree planting in parks, residential and arterial roads, and naturalized areas. These proactive tree planting programs aim to help mitigate the loss of canopy cover due to the EAB infestation.

Are there any pesticides that can be used to control EAB?

A naturally-occurring compound from the neem tree, marketed as TreeAzin has been shown to have insecticidal properties against EAB in ash trees.  At the present time, TreeAzin is the only product registered for use in Canada against EAB that has been shown to be effective in the control of EAB.

EAB larvae tunnel under the bark and feed in the cambium between the bark and wood. To be effective, a pesticide must be injected directly into the active vascular region of the tree and become systemic within the tree.

TreeAzin is a systemic bioinsecticide containing Azadirachtin. A liquid formulation has been developed for stem injection by the Canadian Forest Service in collaboration with BioForest Technologies Inc. which developed the EcoJet System for its application. The pesticide has been fully registered for use in Canada by the Pest Management Regulatory Agency (PMRA) of Health Canada for EAB control in ash trees. TreeAzin inhibits EAB larval development, prevents adult emergence, and provides preventative and remedial treatments.

For more information on this product visit the website.

Is Urban Forestry currently using stem injection of TreeAzin as a control method?

The City’s TreeAzin injection program focuses on the selection of valuable ash trees that are still in good to fair condition and that are not displaying signs of advanced EAB infestation. The selected trees are tagged with an aluminum tag placed on the main stem of the tree and spray painted green.

While pesticide injection can be used to protect trees for a certain period of time, in order to provide an extended control the injection needs to be repeated every two years. In 2014 approximately 4300 ash trees are scheduled for their second round of treatment of TreeAzin.  Another 8700 trees that were injected in 2013, are scheduled to be injected in 2015.


I have an ash tree on my and/or City property. Can I have it injected from EAB infestation?

Homeowners who wish to treat a privately owned ash tree with TreeAzin may do so at their own expense. For more information on TreeAzin treatment and the list of licensed applicators visit the website. The time of the injection is between June and September.

Urban Forestry has implemented a TreeAzin injection program in an attempt to protect valuable ash trees that are located on City-owned property.  Homeowners who wish to have a city-owned ash trees in front of their property treated with TreeAzin are encouraged to contact 311 and request an inspection of a city-owned ash tree.  Forest Health Care staff will inspect the tree and decide on treatment. If the tree meets the required criteria, an aluminum tag with a unique number will be stapled to the main stem of the tree and spray painted green. It is important to evaluate ash trees for their health condition before making a decision on the treatment. The injection is most effective before the tree is infested or at the earliest stages of the infestation. Heavily infested trees with visible signs and symptoms of infestation cannot be protected from further decline.  Ash trees in poor health condition do not respond well to the treatment.

What are the environmental impacts that will result from an infestation of EAB?

Ash forests provide habitat for numerous animals and birds and are integral to the health of soils and watersheds. In natural forests of southern Ontario, ash trees generally form a high proportion of the young tree population. The loss of ash trees will reduce or eliminate food and shelter sources for wildlife, thereby disrupting the ecology of tableland and valleyland forests. Ash trees are also valued as a street tree, being relatively fast growing and one of the very few species that are tolerant of difficult growing conditions typical in urban areas. The loss of the ash species will limit diversity of the future urban forest. All species of ash play an important role in maintaining the health of the environment in which they are located.

EAB Pest Biology

What kinds of trees are affected by the EAB?

EAB attacks only true ash trees of the genus Fraxinus. Both native and non-native ash trees are susceptible. Common ashes found in Toronto include: white ash (Fraxinus americana L.), green or red ash (Fraxinus pennsylvanica Marsh.), black ash (Fraxinus nigra Marsh.) and European black ash (Fraxinus excelsior L.). Other susceptible native ash species are the rarer blue ash (Fraxinus quadrangulata Michx.) and very rare pumpkin ash (Fraxinus profunda Bush), both found in extreme southwestern Ontario. See more information on identifying affected trees (PDF).

What is the lifecycle of EAB?

The adult beetles lay eggs in bark crevices in late May - August and the emergent larvae tunnel into the outer stem of the tree, feeding underneath the bark. Larvae feed throughout the summer and over winter and pupate then emerge as adults between May and August.

Are there any natural enemies (control factors) to the Emerald Ash Borer?

EAB does have natural controls in the form of birds and other animals which feed on the larvae. However, predation has not had a significant impact on EAB populations in North America. EAB does not represent a significant problem in its natural range in eastern Asia. Scientists in Canada and the United States are working on the possibility of introducing natural control agents found in Asia where the EAB population is held in check by natural predators, pathogens, and tree resistance.

Regulation and Disposal of Ash Tree Material

What is the role of the Canadian Food Inspection Agency (CFIA) in control of EAB?

CFIA is obligated under IPPC (International Plant Protection Convention), NAFTA (North American Free Trade Agreement), NAPPO (North American Plant Protection Organization) to enforce regulations for control of invasive pests. CFIA staff may enter private property for the purpose of survey and/or control actions and declare things or places to be infested. Should you have any questions related to the regulations regarding EAB please contact the Canadian Food Inspection Agency at 1-866-463-6017.

As of early 2009, the Canadian Food Inspection Agency does not inspect ash trees suspected of being infested with EAB. Should you suspect that an individual City-owned ash tree or ash trees are infested with EAB, please call within Toronto city limits: 311 for an inspection. Urban Forestry does not inspect private trees. We recommend that you contact a qualified arborist should you suspect that a privately-owned tree is infested with EAB.

How can I dispose of any ash material?

It is possible to move ash material and firewood of any species anywhere within the zone described in the Ministerial Order identified by the CFIA as Emerald Ash Borer Infested Place (See more information from the Canadian Food Inspection Agency (CFIA)). You may dispose of ash wood anywhere within this zone. Ash tree materials include ash trees (whole or parts), ash nursery stock, ash logs, ash lumber, newly manufactured wood packaging made from ash, ash wood or bark ash wood chips or bark chips. Presently, any ash material that meets the criteria for yard waste will be collected during regularly-scheduled pick ups by Solid Waste.

Tree limbs, trunks and stumps are not collected or accepted at City's Drop-off Depots if the diameter of the wood exceeds 7.5cm (3 inches). Exception: Disco Drop-off Depot accepts limbs, trunks, stumps of any size if they are from a City of Toronto Asian Longhorned Beetle (ALHB) regulated area (see the CFIA website for more details).

Material exceeding these dimensions from outside the ALHB area is the responsibility of the resident for proper disposal. EAB infested wood must be disposed of within the EAB regulated area. Arborists typically include wood disposal in the services they provide. You can find tree care companies and arborists in the Yellow Pages under 'Tree Services' or through the Landscape Ontario website.

Can I take firewood (wood, wood chips) out of the City?

Due to the presence of the Asian Long-Horned Beetle (ALHB) and the Emerald Ash Borer (EAB) in the City of Toronto, restrictions related to the movement of certain woody materials have been put in place.

With respect to the EAB infestation in Toronto, the Canadian Food Inspection Agency (CFIA) has instituted a Regulated Area through a Ministerial Order which encompasses the entire City of Toronto and much of southern and southwestern Ontario (see the CFIA website for the Ministerial Order).

There are now prohibitions or restrictions of movement on nursery stock, trees, leaves, logs, lumber, wood, wood chips and bark chips from all ash species, and firewood of all species. Unless authorized by a Movement Certificate issued by the CFIA, their movement out of the Regulated Area is prohibited.

This is necessary to prevent the spread of EAB to un-infested areas in other parts of Ontario and Canada.

Can I get firewood or wood chips from the City?

The City of Toronto is no longer able to provide firewood or wood chips to the public due to the Asian Long-Horned Beetle (ALHB) and Emerald Ash Borere (EAB) insect infestations. After pruning or removing a City-owned street tree, Urban Forestry will not leave firewood on site for residents.