I have a mature elm in my backyard that was probably planted when the house was built in the 70's. We bought it 3 years ago and I have noticed that something is eating away at the bark. There is a reddish-brown streak (almost like what you would see in a human that has blood poisoning) that runs up the bark. I cut off one of the lower limbs that the problem had progressed to. The bark is very "mushy" and looks decayed. Chunks of bark fall off at the affected areas. I cannot see any bugs that may be causing this but I suspect that is the cause. This tree has 2 main branches that extend from the bottom and this is where the main damage seems to be. I am concerned that the tree could "split" at this point if it becomes weakened. I need to know the cause and treatment.




From your description, it sounds like you have slime flux. Elms are very hardy and it probably will survive if you do the following. 
Clean out the wound with a 10% bleach solution (9 parts water, 1 part bleach). After you have cleaned it out, DO NOT let water get on the trunk. Deflect it away. Keep the trunk, the stems, and leaves dry.
If the damage is extensive, I would “lean” on your tree to make sure it is structurally sound. And, of course, if it gets worse, you should think about replacing the Siberian Elm with a more desirable tree.
I hope this information will be of help to you.

Posted on 24 Jun 2009

Julia Tuck
Horticulture Assistant, Utah county

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