Insecticide concentrates for bees . Using a high quality insecticide in the early spring is very important to prevent carpenter bees from boring holes in wood. Spray such places as underside of any wood surface including siding, soffits, overhangs, decks, fence posts, fascia boards and window frames. We recommend spraying during the spring twice at intervals of 3-4 weeks. If the infestation is severe repeat treatment every two weeks.
See: Carpenter Bees for more information on spraying for carpenter bees.