Identifying Wood-Decay Fungi

Xylaria polymorpha – Dead man’s fingers. Finger-like fruiting bodies are found on the roots or near the base of infected trees, typically in groups of three or more. Fruiting bodies are black with a white tip, resembling dead fingers rising out of the tree. All photos courtesy of the author.

Tree care in the urban landscape often involves management of tree health, but due to the proximity to people and property, often trees need to be managed for risk as well. Sometimes this means removal, sometimes it means prevention and sometimes it means taking curative measures.

Wood-decay fungi are a very important category involving risk management, since wood-decay fungi often can increase the inherent risk of a tree. However, fungal identification often is overlooked in our industry. This results in tree care workers misidentifying fungal fruiting bodies, which can mean danger for them and homeowners.

So, on that note, let’s learn how to identify some common wood-decay fungi. All the fungi mentioned here can, potentially, be hazardous to the structure of trees and, therefore, to property, homeowners and arborists.

First, some fungi are more obvious than others, for instance, Ganoderma species, chicken of the woods and Inonotus dryadeus. Some are less obvious and very difficult to ID, such as Kretchszmaria deusta and dead man’s fingers.

Second, timing is imperative for fungal identification. It is important to remember that fruiting bodies of wood-decay fungi can be absent unless conditions are perfect. A good example is Armillaria, which only expresses mushrooms in the late summer to fall.

Key characteristics for ID

Ganoderma applanatum – Known as the artist’s conk. Shelf-like, brown on top, with a white, bottom spore surface. It is a perennial conk that forms a new layer each growing season.

Ganoderma applanatum, known as the artist’s conk.

Ganoderma sessile – The varnish conk. Shelf-like or circular, red shiny top, with a white bottom spore surface. Can be inconspicuous and small.

Ganoderma sessile – The varnish conk.

Laetiopourus sulfurus or L. Cincinnatus – Chicken of the woods. Multilayer shelf fungus, with orange/salmon-colored top, with a yellow/beige bottom spore surface. Mostly found on oaks, but can be found on other hardwoods.

Laetiopourus sulfurus or L. Cincinnatus – Chicken of the woods.

Inonotus dryadeus – Weeping conk. Found at the base of hardwoods, mostly oaks. Has many different shapes, including shelf-like conks and globular conks. When fresh, the conk produces exudate from spore surface. This conk is wood-like and has a cream-colored spore surface, with brown spores.

Inonotus dryadeus – Weeping conk.

Kretzchmaria deusta – Brittle cinder. Fairly inconspicuous, in spring it is gray, with a white border, and as the season progresses it turns black, resembling charcoal on the base of the tree. Found at the base and roots of infected trees.

Kretzchmaria deusta – Brittle cinder. Fairly inconspicuous.

Xylaria polymorpha – Dead man’s fingers. Finger-like fruiting bodies found on the roots or near the base of infected trees, typically in groups of three or more. Fruiting bodies are black with a white tip, resembling dead fingers rising out of the tree.

Lastly, it is important to know that, when dealing with wood-decay fungi, prevention is key. The presence of a fruiting body is proof of infection, but it does not provide information on when the fungus infected the tree initially. And, while there is no cure once a tree is infected with a wood-decay fungus, there are options for extending the life of the tree.

Depending on the type of fungus that is present, you can decide what to do from there. If it is a more aggressive fungus, you may lean toward removal versus possibly just monitoring a less aggressive one.

Hopefully this has been a helpful review of common fungi in our landscape. How many of these have you seen? Get familiar with them all, it could save a life!

Christine Balk is a Certified Arborist and a technical advisor with The Davey Tree Expert Company, a 47-year TCIA member company based in Kent, Ohio.

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