Help! Something ate my apple tree from the inside

[Danaya]

Hi everyone, my heart is in shambles, something made a horizontal hole in my gorgeous mini golden spur tree and then proceeded to make tunnels up and down the trunk. I've tried to fill it with a sealant to some degree, but I don't know if this can help it at all. The tree is so beautiful and bears lovely apples every single year that are so tasty. I really don't know what to do. Shall I leave it to see if it survives (it's just about to start flowering), or shall I try to save it by cutting it down below the level of the damage (there are only 2 very small branches below the point where I guess the tunnel ends at the bottom end)?
Thanks

 

[Chuck]

Apple tree borers. I don't know how to get rid of them except I've known folks who inject the tree with Neem Oil. Perhaps researching tree borers would help.

 

[oneeye]

Borers only attack stressed or weakened trees. Ensure proper watering, fertilization, and pruning to keep your trees in good condition to prevent an attack. Once a tree is attacked it most likely a goner. Apple tree borers, especially flatheaded borers and roundheaded borers, and can weaken or even kill trees.

 

[Danaya]

Thank you for replying. The tree has a nice open shape, and I feed it with chicken pallets. The only thing I'm not able to do lately is watering. It's at my allotment and there is no water supply at the moment. I only had one barrel of rain water, which I used about 10 days ago. I don't know what to do. The tree is so lovely but I don't know if it can survive above the damage level. I don't really want to cut it down, but I don't know if it has any chances, you can see from the picture the proportion of the hole to the size of the tree, and it continues up and down in the centre of the trunk. I at least tried to stop it from going further down with the sealant, but even then, it can just go around it, I guess.

 

[Danaya]

Now I understand why I've seen trees painted white with slaked lime (calcium hydroxide) in other countries. Do you think this might help prevent damage to my other fruit trees?