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Cankerworm Update - Spring 2017

Picture of Cankerworm

The City of Burlington and many other municipalities throughout the Greater Toronto Area have noticed significant tree leaf damage caused by cankerworm, a native insect. Cankerworm occurs on a natural cycle of every eight or 12 years in forested areas, with the last outbreak in Burlington in 2008. Cankerworm is often referred to as inchworms or loopers and may be either green or brown colour. Cankerworm is often confused with gypsy moth because they impact some of the same tree species at the same time.

As part of our Integrated Pest Management (IPM) strategy, city staff will continue to monitor populations throughout 2017 and are meeting with other cities who are encountering similar outbreaks. Picture of tree band If populations reach critical levels that forest health is threatened, the City of Burlington will take action on city-owned woodlots and valleys. At this time, no chemical treatment is planned by the City of Burlington.

Frequently Asked Questions

What is the lifecycle of cankerworm?

In spring the caterpillars feed on leaves from April to mid-June. Then they move into the ground for the next six months to mature into adult moths. The moths emerge from the soil in November - December and lay their eggs in the tree canopy.

Will cankerworm kill my tree?

Cankerworm will not kill healthy trees. Healthy vigorous trees will put out new leaves later in the summer.

What kinds of trees are affected by cankerworm?

Cankerworm is most commonly found on hardwood species such as oaks, maples, elms, and ash.

What should I do if I have cankerworms on my trees on my property?

Cankerworm damage can be controlled on your trees in an environmentally friendly way in the late fall season. A sticky band installed around the main stem of the host trees traps the female moths and prevents them from climbing up the tree to lay their eggs. Female cankerworm moths do not fly and must climb up the nearest tree to lay their eggs. If you are banding trees on your property, make sure you band all trees that are susceptible to the insect. Banding your trees should start in late-October and can be removed by late-December.

Are there natural predators to cankerworm?

Yes, natural organisms such as parasitic wasps, birds, mice, ground beetles, and bacteria usually keep cankerworm population levels in check. However, serious infestations do break out from time to time, usually every eight or 12 years in forested areas. Mild winters, such as the one we recently experienced in 2016-2017, can also help lead to an increase in cankerworm populations.

For more information please visit the Natural Resource Canada Website.

NOTICE - Gypsy Moth Management

Update: The City of Burlington will continue its Gypsy Moth spray program June 13, 2017 weather permitting in Mountainside Park

The European Gypsy Moth (Lymantria dispar) has been present in the City of Burlington for more than 10 years. However, this year in Burlington and neighbouring municipalities,' populations of Gypsy Moth have reached higher levels that require the City to take additional action to control the population.

To protect trees from Gypsy Moth, the City of Burlington is planning to ground spray pesticide as part of an Integrated Pest Management (IPM) program in the affected area of Mountainside Park. This spray program will help control the outbreak of Gypsy Moth and help to protect vulnerable trees from defoliation.

The pesticide,

Bacillus thuringiensis subspecies kurstaki (Btk)-(Foray 48B)--Pest Control Products (PCP) Act Registration Number: 24977 is being applied. The World Health Organization has deemed Btk a safe, biological control made from a naturally occurring bacterium found in soil and only targets defoliating insects.

Ground spraying will take place June 12, 2017. If the scheduled spray is to be cancelled, notice will be provided. Spraying will take place between 6:00 a.m. to 6:00 p.m. at the location on the map provided with this notice.

If you have any further questions in regard to Gypsy Moth, please contact the City of Burlington Roads and Parks Maintenance Department at 905-333-6166. Staff will be glad to put you in touch with the Forestry staff that will answer your questions or provide advice on preventative measures that can be taken to aid in the control of this pest.

Thank you for your cooperation.

Map of Area to be sprayed at Mountainside Park

The trees within Burlington's urban forest provide a wide range of environmental, economic and social benefits, including improved air quality, reduced storm-water runoff, energy savings, noise reduction, natural bird and wildlife habitats, higher property values and overall beautification of city streets and parks.

The city's forestry operations includes the oversight of tree protection and preservation initiatives, including tree protection standards, tree maintenance programs, pests and disease control and tree planting. City staff also offer tree care tips for the public on this website.

We are very proud of our trees, especially those with historical significance on the Burlington Honour Roll of Trees. Whenever possible, we involve the public in the consultation process and surveys, such as the Private Tree By-law Feasibility Study.

Frequently Asked Questions

If I see a large branch of a city tree broken, should I call the city and let someone know?

Yes. Anytime you see a serious issue with a city tree please call the city and let us know. Examples of issues of concern may include a large broken branch hanging over a sidewalk, bus stop or a park bench. Or a tree that has split during a storm, or has uprooted. Please leave a name and number that we can reach you at, in addition to the location of the issue. Also, do let us know the size of the issue, for example, "a hanging branch thicker than an adult's arm over a sidewalk".

I have a very large old tree in my backyard. I am worried it may break in a storm and damage my house. Should I remove it?

Not all old trees are a hazard; often they simply require maintenance from time to time. Large trees provide many important environmental benefits including air quality improvements, stormwater uptake, energy savings (shading and wind buffering), carbon uptake, as well as adding to property values. Contact a reputable tree care company, who can send out a Certified Arborist qualified by the International Society of Arboriculture (ISA) to inspect the tree, including issues not seen by the naked eye. The Arborist may provide strategies including: a Plant Health Care treatment plan; pruning; bracing; a tree preservation plan; or advise you of potential risks and options.

I have a large ash tree on my private property. Should I remove it or treat it?

Trees on private property are the responsibility of the homeowner. You may wish to consider contacting a reputable tree care company with International Society of Arboriculture (ISA) Certified Arborists on staff. Consulting with a Certified Arborist will provide you with options for consideration, based on the health of the tree.

I have a Mountain Ash in my backyard. Will the Emerald Ash Borer attack it?

Emerald Ash Borer is a non native invasive insect from Asia that attacks and kills native ash trees (Fraxinus). Mountain Ash (Sorbus) is not affected by the Emerald Ash Borer.

When does the city prune boulevard trees?

The City of Burlington is on a seven (7) year grid pruning cycle for boulevard trees. The scheduled pruning of boulevard trees includes: raising the canopy above the road and sidewalks; and removal of any hazardous limbs and large deadwood.

We do need the help of the community to inform us of any significant hazards in the trees. If you see an issue which you consider to be a serious risk to people or property, please call us with your concerns and we will be happy to come out and inspect the tree.

Does the city inspect boulevard trees for safety?

Yes. The city inspects boulevard trees for safety, as part of our 7 year maintenance cycle which includes grid pruning. During inspection we look for potential issues which include:

Broken or hanging branches
Dead or dying branches
Cracks in the trunk or at branch unions
Disease and pests
Decay or rot
Sightline issues

If you have concerns about a boulevard tree that you think may pose a serious risk to people or property, please contact the Forestry department and we will come out to inspect the tree.

2017 Emerald Ash Borer

We are evolving our management of the Emerald Ash Borer (EAB) as we see increases in infestation throughout the area.

Emerald Ash Borer is a non-native invasive insect from Asia that attacks and kills native ash trees (Fraxinus). Mountain Ash ( Sorbus) is not affected by the Emerald Ash Borer.

In the past, we treated trees over 20 cm in diameter at breast height (dbh) and removed trees that declined from the infestation of the borers.

For 2017, our program will focus on treating larger trees that are important to our urban landscape and provide the most ecological benefits to our community. The program also includes proactive removal of boulevard trees throughout the city that do not meet the criteria for continued treatment.

Treatment criteria includes:

good health;
good structure;
good location (e.g., not under utilities); and
significant size.
Ash trees over 50 cm dbh will be inspected after leaf out in spring to determine eligibility for continued treatment. Additionally, select streets where the boulevard trees are primarily ash will be assessed for treatment of trees larger than 40 cm dbh.

In 2017, the city plans to remove boulevard ash trees under 30 cm in addition to larger trees which showed significant decline in 2016. We need to do this for public safety as the infested ash trees become structurally weakened. To help compensate for the loss of tree canopy in the city, we will increase our stumping and planting programs over several years. This will help replace the canopy cover and tree loss with trees that will grow to be the future canopy of our city.

Please be patient during this replacement process. Staff are diligently working to source trees that will withstand tough urban conditions so they grow well to maturity. A diversified urban forest will help mitigate future invasive pest threats and planting the right tree in the right place is essential.