Tree Pests and Diseases – City of Burlington

There are many different pests or diseases that can affect the health of our trees. Insects such as the Emerald Ash Borer (EAB), Cankerworm, Gypsy Moth and Asian long-horned beetle can have devastating effects on the health of the urban forest.

Reducing the vulnerability of the city’s urban forest to pests and diseases involves implementation of a wide range of urban forestry practices, including:

  • Plant health care: site-appropriate tree species selection, young tree pruning, watering, and mulching;
  • Improving tree habitat: increasing soil volumes, improving soil quality, reducing above and below ground completion for space and resources;
  • Diversifying the urban forest: establishing underutilized and new native and non-invasive tree and shrub species;
  • Improving knowledge and understanding of the urban forest: conducting a public tree inventory and improved species-based pest vulnerability analysis, increasing monitoring, species and stock suitability trials;
  • Pest-specific management: development and implementation of targeted strategies to mitigate the effects of specific insects or pathogens.

Sticky Banding Demonstration and Poster

Cankerworm

CankerwormCankerworms are native leaf-eating caterpillars, whose population peaks every 10-15 years and can cause widespread leaf damage. Damage in 2017 was significant, and the populations of these caterpillars are expected to peak for one to two years, then declined as natural predators such as birds along with caterpillar diseases reduce the populations naturally. Hardwood trees can survive one to two years of defoliation.

Most common species of trees impacted are:

Common trees that this species prefers to feed on are ash, basswood, beech, black cherry, red maple, sugar maple, red oak, and white oak. It will also feed on the leaves of apple, birch, boxelder, dogwood, elm, hickory, and many other hardwoods.

Will cankerworm kill my trees?
Cankerworm will not kill healthy trees. Healthy vigorous trees will put out new leaves later in the summer.
What is the life cycle 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.
What kind 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 tree?
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 cankerworms?
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.
What can you do for your private trees?

Banding trees is a way to help trap and stop cankerworms from crawling up the tree to lay their eggs. Banding should ideally be done before frost.

Residents are encouraged to visit any of the locations listed to learn how to create a Sticky Band and speak to a forestry expert.

Sticky Band Demonstrations

  • LaSalle Park, 50 North Shore Blvd. W. By the playground: Oct. 15, 2018, 10am
  • Mountainside Park, 2205 Mount Forest Dr. East of the Swimming Pool: Oct. 16, 2018, 10am
  • Sherwood Forest Community Centre, 5270 Fairview St. Parking lot entrance: Oct. 17, 2018, 10am
  • Forestvale Park, 1165 Westhaven Dr. october 18, 2018, 10am
  • Central Park, 2299 New St. By the rear baseball diamond: Oct. 19, 2018, 10am
How to band a tree:
  • Wrap a 10 to 15cm wide strip of polyester or cotton (quilt) batting around the trunk of the tree you are going to be banding – about five feet (1.5m) off the ground. Keep out of reach of pets and young children.
  • Cover the polyester or cotton (quilt) batting with a sheet of plastic wrap or a garbage bag. Allow several inches of plastic above and below the insulation. For larger trees you may need to tape multiple bags together.
  • If you are using plastic bags or plastic wrap, tape the plastic to the tree with duct tape or packing tape. Please do not use nails or staples to attach the plastic to the tree as this will injure the tree.
  • Spread a layer of a sticky substance, such as TanglefootTM (non-toxic, not a pesticide, available at garden centers and hardware stores) as directed or petroleum jelly, on the plastic. This will make the cankerworms stick to the band. Be sure to wear gloves as it is very sticky!
  • Inspect the sticky material regularly and remove leaves, insects and other debris and reapply sticky material if required.
  • Bands should be removed by late spring and reapplied in the fall. It is important to remove the bands to prevent damage or discolouration of the bark.

For a video showing this process please see the City of Toronto instructional video available at:

Emerald Ash Borer

Emerald Ash BorerThe Emerald Ash Borer (EAB) is a non-native beetle that lives in ash trees and lays eggs on the bark and bark crevices. The larvae then tunnel beneath the bark and feed on the layer of live cells between the bark and the sapwood, cutting off nutrients and water to the upper portions of the tree.

Read the Emerald Ash Borer Action Plan

Signs of Infected Ash Trees

Signs of the EAB usually only become apparent once a tree is heavily infested. The following are signs and symptoms your ash tree may be infested with the EAB:

  • The leaves in the top third of the ash tree lose their green colour, thin and die back.
  • New branches begin to grow from the low trunk or roots.
  • White lines or canals are evident under the tree’s bark.
  • The bark begins to split.
  • There are small D-shaped holes in the bark.
  • Increased woodpecker activity on the tree resulting in large holes.

A certified arborist should inspect your tree to confirm the presence of the EAB and to recommend treatment options.

Emerald Ash Borer in Burlington

The presence of the EAB in Burlington was first confirmed in 2010. The EAB has now been identified in pockets throughout the city. The city’s population of ash trees, which make up about 13 per cent of the urban forest, is at risk due to EAB.

Forestry staff are working towards removing infected trees and replanting them with trees that are more resilient to EAB and other potential diseases.

The thermometer below indicates the number of trees planted and removed to date in 2018:

2018 Ash Tree Removal and Replanting in Burlington

2018 totals

Some tree removals deferred to IQ2019 due to contractor issues.

2017 totals

Ash tree removals: 95 percent of target (3296)

Replacement planting: 100 percent of target (715). We have exceeded our planting goal by 11 trees this year!

EAB Quarantine Regulations

To limit the spread of the EAB, the Canadian Food Inspection Agency prohibits moving any species of firewood and ash tree products (nursery stock, logs, lumber, packaging, wood, bark, wood chips or bark chips) from the Burlington and Region of Halton area to any other surrounding regions.

For additional information on the EAB, you can visit the Ontario Ministry of Agriculture, Food and rural Affairs management strategy page or the Canadian Food Inspection Agency.

Gypsy moth

Gypsy moth

Gypsy Moth Aerial Spraying Update

European Gypsy moth, Lymantria dispar, is an introduced pest that impacts trees when larvae emerge in spring and the caterpillars feed on leaves causing defoliation. Oaks are the preferred host species of tree.

As part of Burlington’s Integrated Pest Management (IPM) methodology, Forestry staff assess sites annually across the city and conduct egg mass surveys to determine areas with high potential of significant tree risk. Forestry staff also undertake removal of egg masses where possible. Although healthy trees can generally withstand repeated defoliation, trees which are already in distress from problems such as acute drought, diseases or other pests may die. Generally, healthy trees which are defoliated in spring, will leaf out again by fall. Gypsy moth populations tend to be cyclical, with peaks every 8-12 years, followed by dramatic population decline of the pest.

Treatments are only used when populations exceed accepted thresholds. Treatment of the insect is aimed at keeping larvae populations below risk levels to the tree. The treatment option commonly used is Btk (Bacillus thuringiensis var. kurstaki), a bacterium found naturally in soils. The City of Burlington may use two different methods of application. We may use aerial spray utilizing helicopters, or truck mounted spray application from the ground. Btk works only against the larvae of the target species of insect; it does not affect plants, animals or people. Btk is one of the few treatments acceptable to organic growers as it is a naturally occurring biological organism.

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