distressed plum

[so cal casey]

a few years ago I planted a Santa Rosa plum that had spent too many years in a 15 gallon pot, it's doing fair and producing but the living bark layer had retreated in a couple of spots and exposed bare wood.
An off-white fungus? appears to grow on these spots. is it good and a protection for the bare wood or should I scrape it off and apply tree seal?

 

[treeseer]

a Santa Rosa plum that had spent too many years in a 15 gallon pot, the living bark layer had retreated in a couple of spots and exposed bare wood. ?

Solve the problem ,don't bother treating the effects. Girdling roots are killing the bark. Expose the girdling roots and take a picture and post it here.

Prognosis sounds poor.