You don't necessarily have to back it. Going below the bug damage and chasing a ring in hickory is doable, if like BowEd said, the damage is shallow, only in the first ring or two. In such a case, you could chase a ring and make a selfbow with it, i.e. no backing. Look very closely down all sides of the staves for tiny little holes where the borers would have exited. If they're halfway down the sides for instance, it may be ruined or would require too much work and I probably wouldn't bother with it.
An additional concern for me would be the integrity of the wood otherwise. If it was left with the bark on after being cut, and maintained a high enough moisture content that would allow bugs to attack it, I would wonder if the wood had begun to degrade and lose some of its resilience as well. Just something to keep in mind. The first bow you make from it should tell the tale I suppose. Perhaps you know its full history. If not and your bow seems to take a lot of set for no apparent reason, that could be it.