I think they need good drainage, and the tree is maybe suffocating from the water-drowning-.. I know my Papaya are doing that, they can't stand 'wet feet' either, but they are showing some new growth at the top... maybe digging a trench around your tree would help it dry-out??? sally

How much have you been watering it? When did it start to look bad? How wet is the soil around it?

Normally new trees need to be watered often. If it had been doing well before Debbie then one would guess that it has wet feet. If you planted it too deep the roots could be suffering from lack of air. The root knot should be just at or a little bit above the ground when you plant a tree. If the ground is thoroughly saturated then you can dig up the roots, add some sand to the hole and put it back in.

I'll be interested in what others have to say.

If you have mulch under the tree, take it out and let the ground dry out. Mulch will retain the moisture. Also, listen to what tom123 says above, take your hand and scrape out around the base of the tree so the trunk is open to the air.