Cross posted on Outdoors.

I'm building a new structure in my backyard for my smoker, Blackstone, etc and it's primarily made out pine. The carpenter bees are already starting to visit and I don't want holes in this thing before it's actually completed (or after). Put up traps but they're definitely not interested in those.

What would y'all recommend as a preventative spray?

20yo rough cedar pergolas in Aggieland reporting
Get regular seasonal visits from CBs & BBs but it's still standing ....

What we do:
A. Cedar block top mason jar traps do mitigate this population every year using recommended baits; we are adding 2 more to our 1 since it was 1/3 full this time:
1) dead CBs are a must
2) honey or equal
3) PineSol is a new trial this season

B. Filling holes to kill/deter
1) Carpenter Bee Spray http://rb.gy/ycmkt
2) Roach/ant gels that are top rated
3) Plastic based wood filler
4) Spray bottle of diatomaceous earth
5) UNtested vinegar spray on larvae

C. Repellant sprays (not too effective) - that must be reapplied after washed away by weather/storms:
1) OFF
2) Bronco Fly Spray (Tractor Supply, Amazon) - best for wasp nest sites
3) UNtested as yet: Peppermint, tea tree, almond and citrus/lemon oils

D. Wind chimes = failure

Thanks for the ideas! Didn't even think to add baits to the traps.

I've been battling these and carpenter ants in our stained cedar pergola for years. If you see existing tunnels (perfect circle holes just larger than a pencil), I spray WD40 into the holes until it starts to spill out. Within a few minutes you'll start to see the bees dropping out and dying. I then fill the hole with steel wool then wood filler, then re-stain.

If I start to see activity in multiple areas, I'll nuke the entire structure with Bayer carpenter ant and bee killer, concentrating on the tops of the posts, and any cracks or voids in the wood. It's a con start battle. I've read in multiple places a few good coats of stain is a deterrent, but my experience has been different. They chew right through to the wood.