Two of my apple trees have severe damge caused by rabbits. The cambium has completely gone around the girth up to ten inches high. The older tree is now weeping sap. I know this is bad from reading the literature. 1)Should I put some wrappinrg around them or leave it in the lap of the Gods?. 2) Can I transplant some Sycamore bark around the base.? 3)Whats the chances of survival?
If this is applied soon after the damage, there a very good chance of repair of the bark but if the wound has dried and the cambium is dry and dead, it is less likely.
You could try bridge grafting four or five long apple stems from below to above the damage. Make a sloping cut on each end of the shoot and insert this into a slit in the bark above and below, ensuring the sloping cut is in conection with the slippery cambium under the bark. Do this in April, using shoots cut in winter and stored wrapped in plastic in the fridge. Tie the shoot in place with string and wrap with black polythene.