The City of Selkirk is on the lookout for the presence of the emerald ash borer (EAB), an invasive insect that has been found in Winnipeg and is responsible for the removal of more than 40 infected ash trees in that city so far this year.
Justin Torcia, the city’s Urban Forestry & Naturalization Coordinator, says the insect is on the city’s radar and he recently attended an EAB workshop in Winnipeg. Selkirk’s Street Tree Policy directs city plantings to be diversified so that if an invasive species or disease is introduced to the community, it won’t wipe out large sections of trees at once.
Managing invasive pests
The city has worked with the province for years managing Dutch Elm Disease (DED) and in recent years has been watching for the EAB.
“We will continue to monitor for signs and symptoms of invasive species in all trees and will report any suspected cases to the province so that appropriate testing can be conducted,” Torcia said.
The EAB was first discovered in Winnipeg in 2017 and despite concerns that Winnipeg’s ash trees would be wiped out within 10 years, the bug did not move quickly and as of last year only 22 trees had been infected.
The removal of 40 trees in Winnipeg this year underscores the need to be vigilant and the importance of not transporting firewood. Torcia also said an educated public can help identify potential signs of infestation to help prevent the spread to Selkirk.
“Given that ash trees are located on both private and public properties, increased public awareness and vigilance will significantly improve our ability to detect issues early and respond accordingly,” Torcia said.
How you can help
How you can prevent the spread:
- Do not move firewood between communities.
- Buy or collect firewood locally and burn it where you buy it.
- Inspect your trees regularly, especially in early summer.
- Report suspected infestations early.
- Avoid pruning or transporting ash wood unnecessarily.
If you see an ash tree with at least two of the following signs, it may have an EAB infestation. The presence of just one of the signs does not indicate EAB.
Signs of possible EAB infestation
1. D-shaped Exit Holes — Distinctive D-shaped holes (approximately 3-4 mm wide) in the bark on the trunk and/or larger branches. May be very difficult to find.
2. Bark Splitting and S-Shaped Larval Galleries — Bark may split or peel away revealing s-shaped galleries created by larval feeding.
3. Epicormic Sprouting — New shoots or small branches that grow directly from the trunk or older branches of the tree.
4. Thinning or Yellowing Canopy — Thinning leaf canopy (leaves may also prematurely turn yellow in early summer) and/or an abundance of dead branches appearing in the upper canopy of the tree.
5. Increased Woodpecker Activity — Shallowholes or feeding marks that stop just below the bark (do not go deep into the wood). Light-coloured patches on the outer bark where the normally gray-brown bark appears pale or “blonde” (patches can range from small flecks to larger, irregular areas).
Elm zigzag sawfly
While EAB targets ash trees, citizens should also be aware of emerging threats to elm trees outside of DED: the elm zigzag sawfly.
Relatively new to North America, they target primarily elm trees and behave differently from the EAB. It’s a small insect originally from Asia and despite its name “sawfly,” it is not a fly, it’s more closely related to wasps, though it does not sting.
Its larvae are the damaging stage as they feed on the leaves and can reproduce quickly under the right conditions.
What to look for in identifying the presence of the zigzag sawfly:
1. Leaf Damage
- Distinctive, alternating “zigzag” or serpentine feeding path between leaf veins.
- Elm tree progressively losing leaves.
- Mature larvae feeding is less zigzag patterned and more generalized along leaf margins.
2. Larvae (Sawfly Caterpillar Stage)
- Small (approximately 10-11 mm when mature), green, slug-like with smooth body and slightly darker head capsule.
3. Cocoons
- Small, oval, net-like cocoons (yellowish to brown) found on leaves, bark, or nearby surfaces (including man-made structures).
How to report a possible infestation
Early detection is critical. If you notice signs of infestation, report it as soon as possible.
If any of the above signs are observed on a tree located on private property, please contact Manitoba Forestry’s tree line directly at 204-945-7866 or email treeline@gov.mb.ca. A representative from the province would then conduct an inspection.
If any of the above signs are observed on a tree located on city property (boulevard, median, park, please contact CitizenSupport at citizensupport@cityofselkirk.com or 204-785-4900. A city representative will conduct an initial inspection and, if necessary, coordinate further assessment with the province.
Please include the following information when making your report:
- Location
- Tree species
- Photos of symptoms
- Description of damage
Dutch elm disease (DED) surveys and emerald ash borer (EAB) monitoring are currently underway in Selkirk.