Hi All

I have a n old apple tree with a nice shape and lovely fruit every
year. But it has aon old split that has become open and rotting out
from the heart of it. Its obviously a very old wound but I'd hate to
lose the tree, so was wondering if there is any 'filler' I could apply
to stop further rot. It faces upwards on a horizontal lower main
branch and as such fills with water and debris.

Also, The squirrels like this tree and clamber all over it and strip
bark off which leads to dead branches. What to do here?

Many thanks

Mark