What's wrong with my Planetree?

[TexDex]

I live in East Texas, just outside of Tyler. I have a London Planetree in my front yard that is about 4-5 years old. We bought it from a local nursery as a container tree and planted it in its current location. Last year it lost leaves early and part of the top died and was pruned. This year it was late budding, as were most of the trees in my area due to long winter. When it budded, it initially looked good, but quickly began to experience leaf drop. It has started putting branches out from the bottom that appear to have healthy leaves on them so far, but the top makes small leaves that soon shrivel and die. The upper 3-5 feet appears to be dead.
The tree has been sprayed several times this season with Bayer tree care for possible anthracnose, even tho this tree is supposed to be resistant to anthracnose.
No major landscape changes have been done. The lawn was fertilized this year, but not heavily. My wife has Cannas planted under the tree. Last year it had bottle brush shrubs around it, but those died, presumably from the colder than normal winter, and were removed.
I have inspected the tree closely for lace bugs, but I don't see anything that looks like the pictures I find online. I did find one bug of some kind on it, as well as some spots that look like something insect related. Pics of those are in the link.
I took some pics yesterday, including close ups of the affected leaves, the bug, and a white patch I found on the trunk.
Pics are here:
https://drive.google.com/folderview?id=0B-uHH35cs9_jMWUtRFluRk9EdFk&usp=sharing
I would really like to save this tree, and I hope someone can help!
I have contacted some nearby arborists, but they don't act very interested in coming out for one tree.

 

[Raintree]

Your first clue is it was a container tree. The issues with the leaves are not important. Your troubles lie under the ground. Container trees often become root bound & girdle themselves. This is where your investigation should start, break out a trowel look for a restriction of the root collar.

 

[TexDex]

Ok. I don't really know what to look for, tho. Can you give me a little more insight? I'm not sure exactly what the root collar is. I will do some online research and see what i can find out. My soil is light and sandy, so I would think the roots could grow into it pretty easily. What can I do if I find a root issue?

 

[treeseer]

Attached insight.

Why are canna lilies growing out of the rootball?

 

[TexDex]

Attached insight.

Why are canna lilies growing out of the rootball?

Thank you! The Canna Lillie are my wife's landscaping. I'm guessing we should move them, from your response. Do you think they are harming the tree?

 

[treeseer]

Thank you! The Canna Lillie are my wife's landscaping. I'm guessing we should move them, from your response. Do you think they are harming the tree?

We'll know once we see how the roots look coming off the trunk.

 

[sac-climber]

Attached insight.

Why are canna lilies growing out of the rootball?

Its a new hybrid treeseer, Platanus x cannafolia

 

[treeseer]

Yeah, purple root suckers; wild!

 

[TexDex]

Got to give the file a good read today. It's been steadily raining here. Maybe tomorrow I can do some investigating on the roots. I'll do some careful excavating and post pics of what I find under the purple jungle.....
Funny enough, the Cannas used to be farther away from the tree, but they have expanded.....the wife said she didn't mind moving them, especially if they would harm the tree...

 

[TexDex]

Ok. Did some excavating around the base of the tree. No sign on root girdling. Roots appear healthy. Several large one growing out with a slight downward angle.
So what is the next thing to look for? Most all of the top leaves are brown and shriveled now...bottom leaves appear to still be doing well.

 

[Raintree]

This is a real sad specimen of a tree, it is best that you remove & replace.
If we must continue can you post pics of the root collar that you exposed?

 

[TexDex]

I'm just going to take it out. Whatever the problem is, I think it is too far gone to save now. Thanks for all the help!