I've been watching over the past week as carpenter bees force their way into my hive. I have the entrance reducer in, set to the larger opening, though backed off a little from the entrance. Also a cork hole in the middle box.
Today I decided to go try to do something about it. I have no idea where their colony was, but I have been seeing them crawling on the ivy in front of my girls' hive, so that's where I started. Stomped about 10 there, then covered the area in a couple hundred pounds of sand. Then I set up shop sitting on a cinderblock next to the hive entrance with my pocket knife and killed them as they crawled up the front. Probably another 20 before I had to go.
Everything I have read tells me Carpenter bees are a small colony species, but that was a higher body count than I was expecting. Last year, there were absolutely none. None that I saw anyway.
Any ideas about how to trap or kill more? Can't find the nest, unless its in the old mulch I poured the sand on. And obviously proximity to my girls would rule out pesticide.