I need some help understanding and identifying the kind of borers I
have. Because early on (years ago) Baldo Villegas posted that
generally these creatures are not generally harmful, I have paid
little attention to mine, assuming they would just use the last
half-inch of the cut canes for a place to lay their eggs.

But I am seeing a LOT of borer holes--big wide ones in the ends of cut
canes, almost exclusively on my grafted roses. (Perhaps my ownroots
are too young to have thick enough canes for their liking?)

And recently there was discussion on Gardenweb about a kind of borer
that is not harmless, but bores all the way to the bud union and kills
the plant. How can I tell which kind I have and if I can't does it
mean I have to seal all the holes?