Q: I have a hickory tree that has been attacked by a nasty bug. How can I save it?
A: The splitting of the bark on the trunk makes me suspect this is not a bug infestation.
It looks to me like originally there was root damage nearby and now rot has progressed up the trunk from its origin.
The powdery sawdust at the base looks like the sign of ambrosia beetles, which naturally invade damaged wood.
I think you need to hire a certified arborist to come by and do a health check on the tree. It’s possible the trunk damage is too far advanced to save the tree.