Emerald Ash Borer

Emerald Ash Borer

Emerald ash borer, photo courtesy of Barry Lyons, Canadian Forest Service

What is the emerald ash borer?

The emerald ash borer (EAB) is a highly destructive pest of ash trees. The larvae feed on tree tissues under the bark, interrupting water and nutrient transport, which kills the trees. All ash trees in the genus Fraxinus are susceptible. Although EAB is not known to be in Saskatoon, if established the impact would be considerable as ash make up nearly 23% of the City's public tree inventory.

It can be difficult to detect EAB presence during initial invasions. Some trees only experience dieback when there is a high density of larvae in the tree, making it challenging to identify and contain new infestations before they spread. Once introduced, EAB causes nearly 100% mortality of all ash trees in an area.

What you can expect from us

The City of Saskatoon installs and monitors traps to help detect the emerald ash borer. Additional traps have been installed by the Canadian Food Inspection Agency.

  1. Monitoring for Early Detection of EAB
  2. Inspections of Declining Ash Trees for EAB Activity
  3. Partnerships with Government, Researchers, and Non-Profits to Limit the Spread

Using Woodpeckers to Detect EAB

Image:
Piliated woodpecker searching for emerald ash borer on ash tree. The tree shows light patches of bark (known as blonding), indicating areas where the woodpecker has pecked the bark off the tree in search for emerald ash borer.

Woodpecker searching for EAB. Light patches of bark indicate "blonding", where the woodpecker has chipped away the bark in search for larvae. Photo by dakrock, iNaturalist, CC BY-NC 4.0 / cropped from original

Woodpeckers can be valuable allies in early detection. In areas where EAB is present, woodpeckers often feed on the larvae living beneath the bark. This reveals distinctive light patches bark known as “blonding” as they chip away at the outer bark.

While blonding alone doesn’t confirm EAB presence (woodpeckers regulate the activity of many wood-boring insects), it can be a useful indicator to prompt an inspection for EAB’s distinctive D-shaped exit holes and S-shaped larval galleries under the bark. Early reporting of blonding on ash trees can help us detect emerald ash borer before it spreads, giving us an important opportunity to protect our urban forest.

How you can help us

  1. Burn it where you buy it
    • EAB is spread through the movement of firewood. Prevent the spread by purchasing and burning firewood locally.
    • Do not move firewood from EAB infested regions. The current distribution of EAB can be found here.
  2. Participate in our EAB Woodpecker Surveillance Program

Resources

Images of EAB Activity

Tree trunk showing characteristic emerald ash borer D-shaped exit hole, blonding from woodpecker feeding, and woodpecker feeding cavity in ash tree.
Image caption:

Tree trunk showing characteristic emerald ash borer (EAB) D-shaped exit hole, blonding from woodpecker feeding, and woodpecker feeding cavity in ash tree. Photo by Troy Kimoto, CFIA, CC BY-NC 4.0 / adapted from original

Ash tree trunk showing woodpecker blonding. Light patches indicate where woodpeckers chipped away bark in search of EAB.
Image caption:

Ash tree trunk showing woodpecker blonding. Light coloured patches indicate where woodpeckers have chipped away the bark in search of EAB. Photo by Jim Tresouthick, Village of Homewood, Bugwood.org, CC BY-NC 3.0 US / cropped from original

Branch of ash tree infested with emerald ash borer (EAB) showing characteristic woodpecker blonding. Light areas on bark indicate where woodpeckers chipped away at bark searching for EAB.
Image caption:

Branch of ash tree showing moderate blonding. Light coloured areas on bark indicate where woodpeckers chipped away at bark searching for EAB. Photo by Troy Kimoto, CFIA, CC BY-NC 4.0 / cropped from original

Light blonding from woodpecker activity. Canada Food Inspection Agency agents investigate surroundings for signs of emerald ash borer.
Image caption:

Light blonding on ash tree caused by woodpecker activity. This tree was among those first reported during the Winnipeg detection of emerald ash borer. Reporting small patches matters as they can have a large impact in early detection and control. Photo by Troy Kimoto, CFIA, CC BY-NC 4.0 / cropped from original

Light blonding on ash tree trunk.
Image caption:

Light blonding activity on ash tree trunk. Photo by Troy Kimoto, CFIA, CC BY-NC 4.0 / cropped from original

S-shaped larval feeding galleries of EAB on ash tree trunk.
Image caption:

S-shaped larval feeding galleries of EAB. Photo by Troy Kimoto, CFIA, CC BY-NC 4.0 / cropped from original

D-shaped exit hole on ash tree trunk with dime for size comparison.
Image caption:

D-shaped exit hole on ash tree trunk with dime for size comparison, Photo by Troy Kimoto, CFIA, Bugwood.org, CC BY-NC 3.0 US / cropped from original

Ash Tree Identification

Young black ash showing opposite branching.
Image caption:

Ashes (genus Fraxinus) are one of the few tree species in our area that show opposite branching. Notice how the branches come out at the same height on either side of the tree at the same node. Photo by Vince La Tassa - vlatassa, iNaturalist, CC BY-NC 4.0

Young black ash showing opposite branching.
Image caption:

Opposite branching can be seen throughout the structure of the tree, including the smaller branches and leaves. Photo by François Plourde - renard_frak, iNaturalist, CC BY-NC 4.0

Opposite branching pattern of ash tree set against the winter sky.
Image caption:

Ash trees can be identified in the winter, even without their leaves. Their branches grow in an opposite pattern, which tends to stand out clearly against the winter sky. They typically grow tall and straight, usually with a single main trunk. Photo by Georgiana Antochi-Crihan, City of Saskatoon, CC BY-NC 4.0

White ash buds, with terminal and lateral (leaf bearing) buds labeled.
Image caption:

Buds are also arranged in an opposite pattern. The terminal bud is responsible for new woody growth, while lateral buds hold cells that will form fresh leaves come spring. While leaves drop during fall, buds will remain on the tree throughout winter. Photo by Joseph OBrien, USDA Forest Service, Bugwood.org, CC BY-NC 3.0 US / adapted from original

Green ash compound leaf. Image is annotated to show leaflet count.
Image caption:

Ash trees have compound pinnate leaves. The number of leaflets can vary between ash species, but will generally be either 7, 9, or 11 depending on the species. This green ash leaf has 7 leaflets. Photo by François Plourde - renard_frak, iNaturalist, CC BY-NC 4.0 / adapted from original

White ash compound leaf.
Image caption:

White ash compound leaf. This leaf has 9 leaflets. Photo by François Plourde - renard_frak, iNaturalist, CC BY-NC 4.0

Diamond shaped bark of mature white ash tree.
Image caption:

Mature white ash trees will have a characteristic diamond shaped pattern on the bark. Photo by Paul Wray, Iowa State University, Bugwood.org, CC BY-NC 3.0 US / adapted from original

Diamond shaped bark of mature white ash tree.
Image caption:

Diamond shaped bark of mature white ash tree. Photo by Owen Clarkin - owenclarkin, iNaturalist, CC BY-NC 4.0

Green ash seeds
Image caption:

Ash trees have oar-shaped seeds that can be found in clusters on mature trees. Photo by Paul Wray, Iowa State University, Bugwood.org, CC BY-NC 3.0 US / cropped from original

Video Resources

Find other Tree Disease or Pests