Apple cider vinegar
Dawn dish soap
Mix and add to bee traps located around the decks.
Best time to kill is early Spring (Feb/March).
For carpenter bees, specially made traps are hanging around the deck.
You can also use the battery-powered zapping swatters to kill bees, hornets, and bugs (located in the bin by the front door). For carpenter bees, this zaps them but then you need to squish to confirm the kill. Works well with hornets and wasps also.