Archimedes Plutonium schreef
What I was hoping for information on how to deal with this apple tree in
that it is missing its core. Something has eaten away the entire core of the
trunk at ground level. So the only thing holding up the entire tree is 3/4
of the outer layer where 1/4 is gone and the entire core is gone.

+ + +
That is simple mechanics. Hollowness does not matter much.
If you sink a pipe in a footing of concrete (so that it will stand firm) it
will be quite strong, especially if it has sufficient diameter. In fact a
tower may well be a hollow cylinder and the saying is "a tower of strength".
The missing outer part may matter, but this will depend on the direction the
wind blows.
PvR