The plums look fine, except, they have tiny holes in
them, like a baby worm drilled its way in. I opened
several fruits, to see if there was anything inside,
but I didn't find any worms.

Maybe I've just been misled, but I remember being told
that, at least in the case of apples we were growing,
holes in the apples meant that a worm had *come out*.
So, which fruits did you open up? Those with holes in
them or without?

Tracey