Are carpenter bees in my deck a problem?

A female drills a nearly perfect round hole about 1/2 inch across into unpainted or weathered wood, turns, and tunnels along the grain to lay eggs (Penn State). Young adults emerge in August, then go back into the same wood to hibernate for winter, and come out in spring to do it again. Unpainted deck rails, joists, fascia, pergola beams, and cedar trim are the targets. Woodpeckers make it worse by tearing the wood open to eat the larvae.

Penn State's guidance: do not plug the holes immediately. Treat the galleries first, ideally in spring when you first see activity, again in midsummer, and in early fall. Only after activity has stopped should the holes be filled with a dowel or wood putty and painted (Penn State). Sealed-in bees chew new exits, and untreated larvae emerge in August regardless. Painting or staining bare wood is the one prevention step that works, because they strongly prefer unpainted surfaces.

Cedar shingles, cedar trim, and big wood decks are everywhere on the North Shore, and in towns like Locust Valley, Oyster Bay, and Huntington we see rails and fascia boards honeycombed inside after five or six seasons of reuse. The males hovering at your face on the deck in May can't sting; they have no stinger. The females can but seldom do. The wood is the concern, not the bees.