There are a bunch of carpenter bees eating up my wood deck. My DH sprayed one with about a half can of flying insect spray and he (she?) just laughed it off. Then he turned around and flew right between our heads. Still eating up the deck.
You need some residual pesticide, flying insect spray isn’t going to do it.
Squirt the insecticide into the bored hole (like with a WD-40 thin spray tip) ... Just spraying the outside of the wood - unless the bee’s butt is still visible - isn’t going to do any good.
You can also whack the carpenter bees with a badmitten racket as they comeout.
My own experience with carpenter bees is that spraying them with hornet and wasp spray doesn’t immediately disable them, but if I get a good shot, they’ll fly off, fall to the ground, and eventually die.
I timed the death from insecticide of one carpenter bee a few summers back - more than three hours.
As others suggest, find the holes, spray into the hole (I fill it up). Then, I know some folks who will plug the hole with aluminum foil or something similar. I don’t. If I leave the easy-to-spray holes uncovered, they attract new carpenter bees the following year, and I know just where to find ‘em. LOL.
sitetest
Carpenter bees don’t like paint. (I know, you don’t either!) Find their doorway and plug it up with caulk or wood glue. A little borax in their path can ruin their lives too.
Whatever you do, do it at night or on a cool day. Have some antihistamine on hand just in case.