Mother Nature and old age can do things to plants and insects may be feeding on it because they know it is unhealthy. Unless someone else comes along to say otherwise I'd say cut off all the diseased branches, then paint the cuts and see what happens or contact an arborist through your local garden center. Looks like the roots are surfacing as well. Previous owners didn't seem to care.

Here is a link that might be useful: Propagating Perennials

Mother Nature and old age can do things to plants and insects may be feeding on it because they know it is unhealthy. Unless someone else comes along to say otherwise I'd say cut off all the diseased branches, then paint the cuts and see what happens or contact an arborist through your local garden center. Looks like the roots are surfacing as well. Previous owners didn't seem to care.

Here is a link that might be useful: Propagating Perennials

Your tree definitely has problems... I would agree the bug damage is opportunistic not causable.It does not to me look diseased but could be ...that may be more obvious this summer. The damage is likely heat cold sun wetness bark split possibly in combination with old age .(If it is diseased those brancheds are dead at any rate I'd wait until spring to remove and if they aren't complely dead...I'd leave them and see if they heal) as in pic #3 shows healing has been under way and this has been going on for several years and you just didn't notice cause it was in back of tree (??)(I have had this happen on an older dissectum that loked bad for several years and then I looked at the south west sun side and saw similar damage .don't know why I didn't check before I just thought it was duiseased not sun /winter damaged..mine is still alive and healing)but not doing "well" ...if the bark is attached even by 1/3 it should heal..
Although i have seldom seen this on older trees and is more usual for younger ones...If by june the branch(es) are leafless then it's ok to trim...but it looks like if you do your tree may look a horror film so I hope I am right and it will heal ...the bugs can be treated with seven or other insecticde and hopfully the branches will repair but due to the extensive damage ... I can not promiss that... Others may have a differnt opinion ..david

The arborist came by today and feels that the problems are being caused by a girdling root. You can see it in the second picture above.

I will get a formal estimate on Monday but it appears that I am hiring them for this and other trees on my property. They will prune back the dead wood, cut as much of the girdling root as possible, and apply a fertilizer.

David, to explain, I've only owned this house (and the tree) since November. So it was the previous owners that let this, and other trees, suffer needlessly.

If I can get another few years of enjoyment out of it, I will be happy. In the meantime, I will be scouring these forums for a new Japanese Maple which I will plant in a better spot.

Thanks for your replies!

You did the right thing contacting an arborist ...cause even now I can't see roots in any of your pics let along girdling ones . This ia a problem with long range diagnosis.I guess girdling root(s) could cause stangulation of tree and death of certain parts of it ...still seems strange in such an old tree even if it has been going on for a while... but if it is just one large root you should be able to save the tree ... as I said it may look bad for quite some time but that is perferable to a stump ;>) David

It's a shame. I hope that this tree will recover.
good luck!

nelran