Fungi, Sawdust, and Bleeding, Oh My!

March 15, 2024 · 6 minute read
Fungi, Sawdust, and Bleeding, Oh My!

Have you ever said something so many times in your career that it seems everyone has heard it and you feel like a broken record?  Personally, I have a spiel about trees that I can almost say in my sleep and because of this, I really do feel like I have already said it to everyone and written about it ad nauseam. This was until I was talking with my colleagues and they affirmed that I have yet to share my tree spiel with our Urban Forest Dwellers.

Simply put, there are three somewhat innocuous but very important signs to watch for on your trees that can alert you to an issue well before a tree dies or falls over. If a tree is ever bleeding, has sawdust around the base, or if mushrooms or fungi start showing up, please call an arborist.  These three conditions can sometimes spell death for a tree even if caught early but knowing what is coming can allow for earlier and better decisions to be made regarding the tree’s future.  And of course, there are always nuances to every rule.

The first issue mentioned is bleeding and as with people, it is typically not a good sign when a tree is bleeding. The type of bleeding I am concerned about is on the stem or root flare of the tree and not dripping from the leaves. Typical bleeding can look like foam and effluent bubbling out of the tree or as dark russet to black liquid slowly oozing out of the tree. The more active and foamy bleeding is usually accompanied by a significant amount of insects and a sour smell, which we call Slime Flux.  In simple terms, the tree has been damaged and colonized by fungi and yeast which ferment the sugars produced by the tree to create carbon dioxide and alcohol. The foam is the result of this gas escaping and the smell is from the alcohol which also draws in insects that feed on the alcohol.  In most cases, Slime Flux is not much of an issue unless it spreads up or around the stem of the tree.

The second category of bleeding would be the slow dark oozing type and more often than not, this issue is of more concern than Slime Flux. In almost all cases, this type of bleeding is caused by a genus of fungi-like organisms called Phytophthora which causes a bleeding canker. Creating what we call Phytophthora Bleeding Canker. Usually starting as a small canker, or bleeding spot, near the base or root flare of the tree that spreads both vertically and horizontally on the stem each year. Without treatment this slowly advancing disease will kill off the cambium at the boundaries of the infection until the tree is girdled or more commonly the tree is killed by secondary pests that favor stressed trees. If noted on trees, immediate action should be taken to confirm the infection and determine if treatment is necessary or helpful.

My next harbinger of tree doom is sawdust and this should be a pretty easy one to understand. If there is sawdust around the base of a tree, that means that wood, which is supposed to be inside of the tree, is now somehow outside of the tree. This is obviously not a good thing.

The two likely culprits are borers and carpenter ants as these insects all chew into the trees and push wood out behind themselves to create room to live or feed. If the sawdust is larger and crumbly, very similar to the consistency of Grape Nuts, you are likely looking at carpenter ant debris.  Carpenter ants do not eat wood, unlike termites, and only live in trees where they are able to chew out voids and galleries in the tree. The resulting debris is then discarded by the ants and falls around the base of the tree.  While not an immediate health issue for the tree, it is a sign that the tree now has hollow spots that could lead to premature failure. By identifying this debris, the ants can be treated to kill the colony and the tree can be assessed to determine if the ants increased the risk of the tree.

The other type of sawdust is very fine and can be the consistency of talcum powder either in piles of sawdust or sometimes in what looks like white sawdust tubes protruding from the base of the tree. In either case, immediate action is needed as this type of sawdust is produced by boring insects that chew into the tree and push sawdust out behind themselves. The most common culprits are the native or invasive Ambrosia Beetles which do not feed on the trees but instead inoculate the tree with a fungus that grows to feed a new brood of Ambrosia Beetles. This fungus then does the damage as it blocks the xylem of the tree causing very rapid browning and death. If caught early, treatments can be applied to limit further infestation but no treatments are available to kill the beetles once they have entered the tree. For this reason, if noticed, an arborist should be consulted immediately.

My final sign of concern is a very broad and yet nuanced issue as our world is only possible because of fungi, yet the wrong type in the wrong place can spell disaster for trees. If a mushroom appears to be growing ON the tree, clustered AROUND the tree, or radiating away from the tree in a linear fashion, it is quite likely the mushroom has developed from a fungus that is decaying and feeding on the tree. While this is not always the case, it is much more common to have decay fungus cluster around a tree than beneficial mushrooms. If mushrooms pop up sporadically around your property this is not of concern but a tree being the epicenter of the mushrooms is.

The best way to determine if a mushroom may be a sign of decay is to obtain proper identification of the mushroom as different fungi create different patterns of decay in a tree. When a small amount of Hen of the Woods (Grifola frondosa) is found at the base of a tree, it is likely that some limited heartwood rot is occurring and simple annual monitoring will suffice. Conversely, if a small amount of Brittle Cinder Fungus (Kretzschmaria duesta) is found around the base of a tree, timely removal of the tree should be considered. When it comes to mushrooms, identification is paramount.

When mushrooms are noted around a tree, allow the mushroom to develop as a mature mushroom (not old and rotting) is often easier to identify. Remove the mushroom itself will do no good as it is only the fruiting body of the fungus that is still located inside of and feeding on the tree. It is most useful if an arborist is able to visit to view the mushroom in a timely manner, as the actual mushroom is easier to identify than photos; however, photos can be nearly as good if taken properly.  Be sure to take photos of the mushrooms in situ and up close with a ruler or even a dollar bill for scale. Next, the mushrooms should be removed and photographed to show the bottom as different spore-producing structures under a mushroom are often very important for identification. Be sure to also maintain the entire stem/stalks of the mushroom, if present, as some key identification makers are present on these structures. Finally and most importantly, dispose of the fungus and thoroughly wash your hands in the rare case the mushroom is toxic.

While I jokingly call these signs my three harbingers of tree doom, it is said with a bit of truth. In some cases, these signs are nothing and can be ignored or simply monitored but in others, trees can die or fail. Many of the trees that do die or fail often provide signs well before the actual event and if noticed in time remediation actions can be taken. Keep an eye out this Spring and Summer and don’t hesitate to reach out to your arborist if something looks off.