Doing a little late night brain storming here. I was just out in my store room, putting down some Boric Acid to kill cockroaches, and it reminded me of another use for Boric Acid in killing SHB. The Fat Bee Man (Don) has several videos where he shows using corrugated plastic board with crisco and boric acid as a beetle trap.
I've chased this a bit before, sourcing organic Crisco, but then was stalled at the Boric Acid. Is that considered a treatment? It's not on the list, but the way I think if organics is whether or not it exists naturally. Boric acid from what I understand is a man-made product.
Anyway, I got to thinking how Don's traps work. I believe he said the beetles are attracted to the Crisco for one, and then once they eat through, either accidentally access the boric acid, or are run into the holes by pursuing bees, and so forced to contact it. Regardless, if contact is key, then DE should work as well. I use DE in my garden, but do so sparingly as it can accidentally injure bees if applied wrong or if they just happen to venture over it. To describe for the general audience that might not know, DE on a microscopic level looks like razor blades. To us it's nothing. But to a small insect it's deadly. The sharp nature of the dust scratches and cuts away the waxy coating on an insect causing them to dehydrate. It can also cause great irritation and make insects just scratch themselves to death too.
Look up how Don makes his beetle traps, and consider if you swap the boric acid for DE what would happen:
1) be as effective at killing SHB adults?
2) consider it treatment free as DE is considered organic?
Just some thoughts here, curious how others feel. At present I don't do anything for the beetles. I just try to keep my colonies strong to manage themselves. But I've lost several hives doing this. Somehow, sometimes, the beetles get the upper hand. I've has seemingly strong colonies get overrun by beetles and subsequently swarm out, abandoning the hive for the beetles to reduce to ruin. It sucks! Maybe I'll make a 2014 resolution to not lose a single colony to SHB!