Q.Linden Tree Trunk Damage
I have a ten year old (American) Linden tree that has several deep cracks in the trunk. In one case, it is more than 2/3 of the way through the trunk and the insides are soft (mushy) and can be easily scooped out with a finger. I noticed what looked like earthworms inside, less than an inch long. Can this 16 ft. tree be saved?

Certified GKH Gardening Expert
It is borers. I would recommend neem oil to treat the plant. Neem oil is a systemic pesticide, which means the tree actually absorbs it and it flows through the tree, getting even pests on the inside of the tree. If this tree is important to you, I would also recommend having an arborist look at it.