Mushrooms on an Elm tree

Asked July 24, 2018, 3:09 PM EDT

I have an Elm tree that gets a lot of mushrooms growing on the lower part of the trunk. The trunk also has a lot of small holes, about 1/8" across, and a lot of medium size ants going up and down the trunk. The Japanese beetles seem to like the leaves as there are quite a number of leaves on the ground that have been eaten by them. Are any of these a bad sign for my old Elm? Thanks Jim

Hennepin County Minnesota

3 Responses

Sometimes mushrooms growing on a tree are an indication of decay - Is it possible for you to upload a photo of the mushrooms?

Are the holes you are seeing in rows? If they are, I would guess that they're cause by Yellow-bellied Sapsuckers: https://www.audubon.org/field-guide/bird/yellow-bellied-sapsucker. I suspect the ants you are seeing are attracted by the sap coming from these holes. You can discourage the birds from your tree by warping it in burlap or hard ware cloth. I've also heard that putting a fake snake or bit of rubber hose in the tree has been effective in scaring away the birds. I know it sounds silly, but a low cost thing to try!

The mushrooms that are left are a couple of weeks old. I destroyed the others.
The holes are random and not in a line.

I suspect heart rot in the tree. You may want to consider having an arborist come out and give a consultation.

The ants are probably carpenter ants taking advantage of the rotting wood. Since the holes are seemingly at random, they really could be anything that is taking advantage of the weakened tree.

Here are some articles on the topic:
https://extension.unl.edu/statewide/buffalo/Heart%20Rot%20in%20Trees%20November%2015%202014.pdf
https://www.gardeningknowhow.com/ornamental/trees/tgen/heart-rot-in-trees.htm