Brittle Cinder Fungus – (Kretzschmaria deusta)
Brittle cinder fungus (Kretzschmaria duesta), also known as “burn crust” fungus, is a common soft rot pathogen that primarily affects broad-leaved trees. The Latin name deusta, meaning “burnt”, refers to the fungus’ distinctive cinder-like appearance, making it and aptly named and visually recognizable tree pathogen. It is particularly found on hardwood species such as beech, maple, oak, linden & elm trees. The fungus begins as a white-gray, powdery growth but darkens with age, eventually turning black and bumpy. In its later stages it can resemble creosote. Despite infection, trees can maintain a healthy outward appearance before showing signs of structural weakness.
The fungus spreads through both spores and direct root contact. During its reproductive phase, it releases microscopic spores that can be carried by wind or water, allowing it to colonize new trees. The spores settle on weakened or wounded areas of the tree, where they germinate and begin to infect. In addition to airborne dispersal, brittle cinder fungus can also spread through root-to-root contact with already infected trees. Once established, the fungus causes soft rot by breaking down cellulose and lignin within the wood, leading to brittle and weakened structures. This makes infected trees more prone to failure, especially during storms or strong winds. The fungus can persist on dead wood, continuing to decompose the material long after the tree has died. This ongoing decay can lead to sudden tree failure, posing risks to people and property.
Brittle cinder fungus is commonly found in temperate regions of the Northern Hemisphere. The fruiting bodies emerge in the spring and early summer; although older blackened fungal growths can be found throughout the year. Because the fungus spreads through spores and root contact, proper tree maintenance, including avoiding injuries to the bark and roots, can help reduce the risk of infection. However, once a tree is infected, removal is often the safest course of action to prevent unexpected collapses.
