Two years ago, one of my apple trees developed a strange illness then died that winter.
During late spring and summer a few of the leaf bunches at the ends of branches turned red/orange, then brown and died. It never spread to the whole tree, but that winter the tree went into hibernation then died over the winter. There is another apple tree of a different variety not more than 20 feet away that was not affected at all.
I have elected not to replace the dead tree, but this has been baffling me since. I lived in one of the northern suburbs cities around Dallas
It sounds like it was Cedar Apple Rust.
You may want to replace the dead tree to benefit your remaining tree, as a pollinator.
I would suggest checking with your local County Extension Office for a list of tree varieties known to thrive in your growing zone.
You can also check with local garden centers and greenhouses.