Question
Hello Dr. Vann:

I live in Southern California in the "Inland Empire" about 70 miles east of Los Angeles, and in my yard are a number of trees of different species.

About a week ago I discovered that one of the trees that I hadn't been paying attention to was completely dead. It's a tall, thin, 50-foot poplar or alder-type tree (I'm not sure of the species), about 35 years old.

Though the lawn and the shrubs around it are green (they all get plenty of water), this dead tree is completely dried up, the dead branches are brittle, the cambium layer on the trunk is dead, and when I pull at the bark on the trunk, it breaks off in big sheets.

Puzzled by the situation, today I began looking over my other trees, and discovered 2 large dead branches on a 35-year old English walnut about 50 feet away from the dead Alder-Poplar.

When I pull at the bark on the dead branches of this English walnut (the bark is much thinner like paper), it comes off in sheets too, and under the bark, where the cambium layer should be, is a jet black mold (or at least it LOOKS like a mold) that comes off all over my fingers and feels about the consistency of damp gunpowder. It rinses off of my hands with water.

This mold, disease, or whatever it is, seems to be progressing from the ends of the branches down toward the trunk, as if it started at the ends of the branches.

Assuming that this English walnut is beginning to succumb to whatever killed the Alder-Poplar, can you tell me what's happening, what this disease is, and what I can do to stop it, and save this English walnut and my OTHER trees that don't seem to have been infected yet? Your advice will be greatly appreciated.

P.S. I have a scientific background, and I'm the author of what remains, since its 2004 publication, the best-selling book in the hobby of amateur rocketry.

It's titled "Amateur Rocket Motor Construction". If you Google the title, you'll find it all over the Internet, and you find some excellent reviews on Amazon.com.

In exchange for your advice, I'd like to send you a signed copy. Even people who aren't interested in rocketry have told me that the first chapter that deals with the history and politics of the subject is quite interesting.

David Sleeter/Moreno Valley, CA

Answer
David:
I expect the black substance can be any number of fungal organisms that have become established on previously decayed wood.  These are probably the result, not cause of the decay.  These organisms have the ability to utilize dead material as a food source and are what we term opportunistic or secondary fungi.

I cannot connect the demise of the walnut and poplar as coming from the same specific biotic disease, but rather from different sources. Often there is a progression of fungal or bacterial organisms that leads to decay.  Most of the time this is initiated by stress to the tree and the presence of a wound from the past.  Prevention of bark damage is important for the health of trees.  Internal decay is a slow, but progressive disease.  Good tree fertilization (based on a recent soil test) in conjunction with appropriate watering during hot/dry conditions is the only thing we can do to increase the life span.  There will ultimately come a point where the tree may become a hazard to person or property and need to be removed.

Hope this helps!

Steve