When I went out to water my raspberries this afternoon, I saw the back end of a little bug disappearing into a hole at the top of one of the canes. Here are the holes:
And here's the bug:
It's about 3/4 cm long, with a narrow waist like a wasp (but not as long as a blue mud dauber), and iridescent blue. I'm pretty sure they burrowed in, because there's a little pile of what looks like sawdust underneath, and the fourth cane didn't have a hole (not did any when I bought them).
I'm in the mid-Atlantic USA.
What are these little beasts? How bad are they? What can I do about them?