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Invasive Species in Ontario

OFT’s Farmland Conservation Specialist, Joel Enman, recently attended several sessions of the 2024 Invasive Species Forum, which provided presentations on invasive species in Ontario.

This forum is held annually by the Invasive Species Centre which is a not-for-profit organization that aims to prevent the introduction and spread of high-risk invasive species in Canada by connecting stakeholders with knowledge and technology. The forum included speakers from across Canada and neighboring U.S States to discuss advances in invasive species monitoring, prevention and management.

Topics included research advances in monitoring for invasive species using eDNA, satellite imagery, AI, and new technology for testing for invasive species presence. The forum also covered updated research on the spread of pests and invasive plants which have negatively affected Canadian ecosystems, including Emerald Ash Borer, Asian Long-Horned Beetle, Water Soldier, Elm Zigzag Sawfly, Dog Strangling Vine and others.

The forum also discussed a newly introduced invasive species into Ontario, known as Oak Wilt (Bretzielle fagacearum) which was first found in Ontario in 2023. Read more about this fungus below!

Joel has shared that he learned so much from attending these sessions and would like to thank all the speakers who shared their lessons learned, research, and experience managing these species!

Invasive Pathogen: Oak Wilt (Bretzielle fagacearum)

What is it?

Oak wilt is a fungus that grows on the outer sapwood of oak trees, restricting water and nutrient flow through the tree in the vascular tissue. Oak trees attempt to block the fungus which further restricts nutrient and water flow leading to the death of oak trees.

Where is it?

Oak Wilt has been found in 24 states in the U.S and was first identified in Niagara Falls, Ontario in 2023. Since it was first identified in Ontario it has also been identified in the Township of Springwater in Simcoe County and Niagara on the Lake.

How is it spread?

Oak Wilt has 3 main methods of transmission:

  1. Root Transmission – Oak Wilt can be spread through root-to-root transmission. it spreads underground in stands of oak trees as many oaks can share nutrients through underground root grafts.
  2. Pressure Pads and Nitidulidae Beetles – After a year of infection with Oak Wilt, the fungus can produce fruiting bodies that create pressure pads which form under the bark causing it to crack. These fruiting bodies produce a strong fruity or wine-like odor that attracts Nitidulidae beetles that feed on the fruiting bodies.  During feeding, the beetles get coated in spores and can then transmit the spore to other oak trees through fresh wounds in the bark often caused by construction, storm damage or pruning.
  3. Firewood – Oak Wilt can also be spread through firewood that is infected with the fungus. Pressure pads do not show up until a year after tree is infected so if a dying tree is cut down for firewood and the owner is unaware the tree is infected with the fungus it can be spread.

How to identify Oak Wilt?

  • Discoloration of leaves that starts from the tip of the leaf moving to the center
  • Early leaf drop-leaves begin to fall in June and July
  • Leaves begin to die from top of the tree downwards
  • Cross section of the branches often have a dark rung which occurs from the wilt
  • Bark cracking from the formation of the fungal fruiting bodies
  • Black, grey or white coloured fungal matts accompanied by sweet odor

What you can do?

If you see the signs of oak wilt occurring on your property or in public spaces you can report this. Contact the Canadian Food Inspection Agency who will do an assessment of the tree.

Toll free: 1-800-442-2342

Avoid pruning oak trees between April and November because this is when the transmission period is for Nitidulidae beetles. The beetles are unable to chew through bark. The only way for them to enter in through fresh wounds from pruning or storm damage.

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