One of the limbs has a hole in it, about the size of a softball. This tree is so big, it's hard to see much but the base of the trunk. Like all giant pecan trees, it throws branches down occasionally, but nothing unusual from what very little I know about such things. I know it's impossible to say over the internet "yes, your tree is dying," or, "no, it's fine and will live another 50 years for sure." Just wondering if trees that DO live another 50 years go through times when they look like this one. And yes, I'm sure it was raining the whole time they were supposed to be pollinated. It rained from mid-june to mid-Aug., hardly missing a day, sometimes several times a day. Thanks for your input! As I was clicking submit, I remembered, saw my Mom's tree is FULL of nuts the other day... a few miles away, so same weather! This post was edited by purpleinopp on Mon, Sep 2, 13 at 10:19

Appears to be an old wound. Wood underneath damaged bark died. Then borers moved into the dead wood. Any reason for the plastic strap other than to strap the tree to the stick?

The leaning makes me think maybe it is root-bound from having been left too long in a pot years before having been planted where it is now. This is a very common occurrence that seems therefore likely to be involved when an established tree develops such problems. If it were mine I would carefully dig down a bit to look and see if there is a girdling root below the rotting area. In what is perhaps a similar situation friends had a long established snake-bark maple pinch itself off on one side after many years in place. The section of trunk directly above the clearly visible, above ground constricting root (it looked like a boa or python wrapped around prey) turned black and oozing once things got to that point. And the tree's crown began to decline - so they cut it down. This was too bad as it was a somewhat unusual tree right off the corner of their wrapping deck.

Sun burn could cause this as well. Given the canopy cut, that is definitely a possibility. If that is the primary cause, paint with a diluted latex paint. When did the bark damage show up? The upper picture is more recent as the trunk picture had calloused over along the at least part of the damage. Since it is at ground level, one of the problems is that the core wood will attract pests - that eat the wood, or eat the rotting wood. If the base trunk has been that way for quite some time, you may have some pests within the wood, contributing to issues.