Emerald ash borer and other tree pests

The emerald ash borer (EAB) is a highly destructive, non-native, wood-boring beetle that affects all species of ash (Fraxinus spp.) trees, ultimately killing them. The City has monitored its presence since 2002. Now established, EAB is expected to destroy all of Guelph’s untreated ash trees.

Ash trees on your property

If you have an ash tree on your property, please have it inspected by a certified arborist, and consider treating or removing the tree. Visit Ontario Trees for help identifying ash tree species.

Treating emerald ash borer

TreeAzin® is recommended by the Ontario Ministry of Natural Resources and the Canadian Forest Service as the best option for treating against emerald ash borer.

Treatment must begin before the tree is heavily infested. TreeAzin® must be injected by a licensed pesticide applicator using a special device, and injections are required every two years to keep the tree healthy.

For more information including a list of service providers, visit bioforest.ca.

Removing trees infested with emerald ash borer

Trees affected by emerald ash borer will eventually die, but you don’t have to remove them until they become a safety risk. As the property owner, you are responsible for removing and disposing of dead, hazardous limbs and trees. To have infested limbs or trees removed safely, contact a certified arborist or forester.

We encourage you to replace any tree you remove with a native tree species. 

If your property is property larger than 0.2 hectares (0.5 acres) please learn more about Guelph’s Tree Bylaws and permits before removing any trees measuring at least 10 centimetres in diameter at 1.4 metres above the ground. If the tree(s) are infested with emerald ash borer, you may be eligible for an exemption.

Signs of emerald ash borer

Signs of emerald ash borer usually become obvious when a tree is heavily infested:

  • Loss of leaves and dead branches in upper part of the tree,
  • Yellowing leaves,
  • Adult beetles feeding on leaves,
  • Unusually high woodpecker activity,
  • Long shoots growing from the tree trunk,
  • Vertical cracks in the tree trunk,
  • S-shaped tunnels under the bark (filled with sawdust), and
  • Small D-shaped holes

Not all ash trees that are losing their leaves are a result of EAB. Some instances may be a matter of general ash decline.

Ash trees on City property

Knowing about 10,000 City-owned trees will eventually die, Guelph’s plan to manage EAB focuses on reducing the risk of personal injury and property damage, minimizing damage to our urban forest, and preparing for recovery.

The principles of Guelph’s emerald ash borer management plan are to:

  • Ensure safety of people and property.
  • Help people understand options for treating or removing ash trees on their properties.
  • Treat as many City-owned ash trees as feasible; only invest in treatment for the very best candidates.
  • Leave affected City-owned ash trees standing as long as they are safe to stand, to maintain environmental benefits for as long as possible.
  • Prepare for recovery before ash-tree decline, if possible.
  • Protect natural areas from ecological degradation caused by EAB infestation.

Learn more about Guelph’s emerald ash borer plan

Termites

Learn about Guelph’s termite management program

Other tree pests and diseases

Please contact us if you suspect a tree pest or disease on City property.

In addition to Guelph’s emerald ash borer management plan, the City actively monitors for signs of other insects and diseases that could threaten our urban forest.

If we suspect a tree pest or disease is present on City property, we conduct a tree inspection. If an invasive pest or disease is confirmed, we report the matter to the Canadian Food Inspection Agency.

In cases when the health of a tree is threatened, we would take appropriate action.

Most tree pests and diseases like aphids or box elder bugs, are native, non-invasive and do not significantly impact tree health or structure.

For more information

Parks Operations and Forestry
[email protected]
519-822-1260 extension 5626