Oak Wilt

Description

Oak Wilt is a fatal vascular disease of oak trees caused by the fungus Bretziella fagacearum.This fungus infects the xylem (water-conducting tissues), obstructing the flow of water and nutrients which causes leaves to become discolored and wilt rapidly, eventually leading to the tree’s death. This disease impacts red oak species most severely, often resulting in tree death within a single season.

  • Scientific name: Bretziella fagacearum

  • Common name(s): Oak Wilt

  • French name: Flétrissement du chêne

  • Regulatory status: While not federally regulated in Canada, Oak Wilt is closely monitored by provincial authorities due to its severe impact on oak trees and related ecosystems.

Oak Wilt leaf

© csledge via iNaturalist.org, used under CC BY NC

Introduction and Spread

Originally identified as a pathogen in the United States, Oak Wilt has been a significant concern in areas ranging from the Midwest to the southeastern regions. It spreads primarily through root grafts between neighboring trees and overland by insects such as the oak bark beetles and sap beetles, which carry fungal spores from infected to healthy trees.

Distribution

In Canada, Oak Wilt is relatively new, with detections in Ontario near the US border, where it was established. Its presence poses a serious threat due to the mobility of the disease through natural and human-assisted means.

Habitat

This disease thrives in areas populated by oak trees, affecting different species with varying degrees of severity. Red oaks are particularly susceptible and can die quickly once infected, whereas white oaks may exhibit more resistance and slower disease progression.

Identifying Features

  • Symptoms: Begin with wilting and bronzing of the leaves at the crown, progressing downwards. Leaves often show a characteristic pattern of discoloration, progressing from the edges inward.
  • Fungal mats: These may form under the bark, producing a distinct smell and exuding spores that attract beetles, further facilitating the spread of the disease.

Impacts

  • Ecological: Disrupts local ecosystems by killing large numbers of oak trees, which are crucial for biodiversity and ecological stability.
  • Economic: The removal and management of affected trees can be costly, especially in urban areas where oaks are commonly planted for aesthetic and environmental benefits.

What You Can Do

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Buy Local Burn Local

Buy firewood close to where you plan on using it to avoid transporting unwanted invasive species and diseases. Leave unused firewood on site.

1. Gauthier, M. K., Bourgault, É., Potvin, A., Bilodeau, G. J., Gustavsson, S., Reed, S., … Tanguay, P. (2023). Biosurveillance of oak wilt disease in Canadian areas at risk. Canadian Journal of Plant Pathology, 46(1), 27–38. https://doi.org/10.1080/07060661.2023.2261890
2. Karrie A. Koch, Gina L. Quiram, Robert C. Venette, A review of oak wilt management: A summary of treatment options and their efficacy, Urban Forestry & Urban Greening, Volume 9, Issue 1, 2010,Pages 1-8, ISSN 1618-8667, https://doi.org/10.1016/j.ufug.2009.11.004

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