hmm, if it was composted manure, I wouldn't think it would cause that much of an issue. Especially in sandy soil. Plum roots can be really aggressive and spread like crazy (suckering is very common) even in clay soil. I would expect your trees roots to be well outside the planting hole by now.
Brenda Groth wrote:
there is a surefire way to tell if the tree is still alive.
Take your fingernail and lightly scratch the bark, if there is some green "life" left in the tree, leave it..
this looks like good info for diagnosing problems but I don't know if this site offers any organic solutions.you could try identifying the problem then searching for an organic solution using the search bar HTH