🍄 The Story Written on Beech Bark

The Long Partnership Behind Beech Bark Disease

During the colder months, I often notice the fruiting bodies of the beech bark canker fungus on American beech. Across the Northeast, beech trunks commonly bear a rough gray armor of cankers, the visible result of a long standing interaction between an invasive insect and a pathogenic fungus. Together, beech scale insects and the fungus Neonectria faginata cause what is known as beech bark disease.

The process begins when beech scale insects feed by piercing the bark, creating thousands of small wounds. Neonectria spores exploit these openings, invading the living tissues beneath and killing localized areas of phloem and cambium. Early symptoms appear as scattered white flecks of scale on bark that was once smooth. As the disease advances, the bark becomes pitted and irregular, and during winter the fungus produces clusters of minute red fruiting bodies on cankered areas.

This disease complex arrived in Atlantic Canada in the late nineteenth century and was established in New England forests by the early twentieth century. It has since spread through much of the northeastern range of American beech, killing many large canopy trees. The loss of mature beeches alters forest structure, reshaping light availability, understory plant communities, and wildlife habitat.

Not all beeches succumb. Some individuals show partial resistance, limiting infections and keeping cankers small and contained. These survivors may play an important role in shaping the future persistence of American beech and its fungal antagonist in northeastern forests.

References 

Cale, J. A., Garrison-Johnston, M. T., Teale, S. A., & Castello, J. D. (2017). Beech bark disease in North America: Over a century of research revisited. Forest Ecology and Management, 394, 86–103. https://doi.org/10.1016/j.foreco.2017.03.031

Beech Bark Disease: Landscape: Center for Agriculture, Food, and the Environment (CAFE) at UMass Amherst. (2023, December 4). https://www.umass.edu/agriculture-food-environment/landscape/fact-sheets/beech-bark-disease

📷 Beech Bark Canker Fungus (Neonectria faginata) | © Claire O'Neill, please credit accordingly.