If the leaves are above the graft line you are in luck. And you are certain that the remaining 60% is dead simple chop of the dead 60%.
You will now have a heavily pruned apple tree. It will grow and produce just as well as a regular apple tree.
Location: Vermont, annual average precipitation is 39.87 Inches
posted 4 years ago
Yup, apples can take really heavy pruning. I'm heavily pruning some apple and pear trees to create a living fence (espalier). One of my trees ended up looking like a stick in the ground last spring but it's got plenty of new growth to work with this year.