Repairing apple tree wound
I have a wound on guessing 7-10 year old Sweet sixteen apple tree. The wound seems to be on the graft There are so many miss informed solutions so I wanted to see what a expert would say. Should I seal the wound? if so what should I use? I have seen foam, tar, brick and cement, window caulking, bio-degradable plastic wrap, so much more.
Tree sealants are not recommended as, except in oaks pruned during the season for something called oak wilt, they can cause more problems than they prevent. Trees naturally seal off damaged areas. Any sealant can cause the area to rot rather than heal.
Your tree has extensive damage. It looks like at least half of the trunk's diameter has been damaged. Trees use the green layer right under the trunk to move food from the roots to the branches and leaves. Once this "highway" is damaged, the tree cannot re-establish this path, even after it seals off the wound. I don't know what is happening on the back side of the trunk, but only undamaged bark can feed the tree. Since there is so much damage on your tree, it should be removed as it is basically dead already. The tree may leaf out normally as energy would already been stored in the buds, but there will be no way for the tree to continue to feed itself.
The damage looks like it caused by fireblight, which is a serious and often fatal condition. See https://extension.umn.edu/search?query=fireblight . Again, the tree should be removed. Sorry!