Glad I saw this post. I was thinking of starting a thread on this.
Sometime in April I pulled a frame that had both adult and young larva from my one overwintered hive. I destroyed this frame and dropped in a foundationless frame. This was the last time I have seen SHB's on any of my hives. I split that colony, got a new package in late April, and caught a swarm in May, so now I have 4 colonies. I did an indepth inspection today and saw no SHB's. Not as good as Matt (one among 225 colonies), but I'm not complaining. I guess it was the brutal winter that took out any feral SHB's.