What’s this growth on my cedar elm tree?

Thanks to Kathy Bartsch for this great question! Kathy writes that over the last several months, she’s noticed what looks like a yellowish growth on one of her cedar trees. When she pulled a bit of it off, it had a very tough, rubbery consistency.  Kathy also notes that the substance is located on spots where limbs have been removed, and so she wondered if it may be the tree’s way of healing, or if it’s quite the opposite. Kathy says that the foliage is still green and there isn’t an unusual amount of leaf drop. A nearby cedar doesn’t have this problem at all, but she recently noticed an old pecan stump is now encrusted with this same “blob.”

Well Kathy, unfortunately, this is a fungus, and it’s feeding on the interior of your tree. Most fungi feed on dead tissue, not living. And since the interior of your tree, the wood, is dead, by definition, if fungal spores are able to find an entry point and the environment is right (in other words, overly humid), the spores can grow and will begin to digest a tree from the inside out. The entry could be a pruning cut or any other type of physical damage that creates an entry point for the spores.

The good news is, if the surrounding trees don’t have any open wounds, the fungus is not “contagious.” The old pecan stump nearby is simply a more exposed, and more common, food source for the fungus, and fungal feeding on dead logs is part of the natural process of decay that occurs in the woods. For the tree in question, you may either remove it now, or take an observational approach, waiting until it begins to decline to remove.