Question
QUESTION: I have a Wickson plum tree, about 25 years old and generally seeming to be in good health. About a month ago I noticed some questionable bark, which I lifted off very easily.  Underneath was a powdery magenta layer, which I'm assuming was spores.  There was no green cambium apparent.  The patch of loose bark (which I removed) is about 1' long and perhaps 2-3" wide at the widest point, fairly low on a major branch that is about 5" in diameter.  The branch with the magenta powder doesn't show any sign of disease (yet) other than the bark.

A number of years ago, I thought the tree had silver-leaf disease (silvery leaves, brown stain in the wood), and I pruned accordingly.  I've seen no sign of silvering since then.  A local Ag Extension guy said silver-leaf doesn't occur here in California, but I still stick to summer pruning for this tree.  

I'd be grateful for any information!

Kate

ANSWER: Kate:
Good fertilization schedules (based on a recent soil test) plus avoiding damaging the bark with things like string trimmers and lawnmowers can go a long way in helping a tree last a long time.  Having someone examine the tree is a good thing. They can help recognize otherwise problems from showing up..  I wish many times for a magic bullet!!

Steve

---------- FOLLOW-UP ----------

QUESTION: Could you give me more specific information about what might be causing the loose bark and magenta spores?  (E.g., what diseases have these symptoms.)  Thanks-

Answer
Kate:
Many things may be acting together or separately in your case. A diagnosis is impossible without an on-site inspection and/or laboratory exam. Soon after a fungal infection, many "secondary" microorganisms, insects etc often move in to those areas- making it difficult to impossible to determine the original causal agent. Consider contacting your local county Extension office to arrange for a visit.  You can also seek assistance from a local garden center with a long standing reputation.

Regards
Steve