Do Carpenter Bees Come Back Every Year? Yes, to the Same Holes

Because the tunnel is where they were born and where they spent the winter. Ohio State's fact sheet explains that the new adults need shelter during the winter and hibernate within their old nest gallery. Penn State says the same: young adult males and females hibernate in the tunnels, emerge in spring, and then clean out and enlarge the old tunnels or excavate new ones. Maryland Extension adds that many tunnels are lengthened and reused year after year by successive generations.

So the bees you see in April are last year's offspring coming out of last year's holes. They are not choosing your house again. They never left it.

One generation a year, on this schedule. Adults emerge in April and early May, according to Ohio State and NC State. Through May and June the female tunnels and provisions 6 to 8 chambers with pollen and nectar, laying an egg in each, per Penn State. Through July and August the larvae feed inside the wood and the outside goes quiet, which is when people assume the problem is over. Penn State says the newly developed adults emerge in August, feed on nectar, and return to the tunnels to overwinter. Then it starts again.

The eastern carpenter bee is the species here. Cornell's IPM program describes it as robust, three quarters of an inch to an inch long, with yellow hairs on the thorax and a shiny, non-fuzzy black abdomen.

Yes, slowly and cumulatively. The entrance is a nearly perfect round hole about half an inch across, per Penn State. Clemson describes the tunnel going in about an inch, then turning sharply at a 90 degree angle to run with the grain. Ohio State puts a first year gallery at 4 to 6 inches. NC State says that if the same entrance is used for several years, tunnels may extend several feet in the wood.

The damage people actually see is usually not the bee's. Cornell notes that woodpeckers add to the damage when they search for bee larvae and create large openings in the wood. NC State also describes the yellowish brown staining from waste on the wood below the hole. A board with a few neat holes in April can be a board with a torn-open gallery by August.

Because the bees are still inside. Maryland Extension is explicit: tunnels must be pre-treated with a pesticide before caulking or the bees will chew through the plugs and reemerge. Clemson adds that trapped adult carpenter bees can excavate new openings. Plug an untreated hole in April and you get a chewed plug or a fresh hole beside it in May.

Inspect every board. We check fascia, soffits, deck rails, pergolas, siding trim, and the undersides of anything wooden, and mark each hole.

Treat the galleries. An insecticidal dust goes directly into each nest opening, which Penn State and Ohio State both describe as the effective method because it stays active inside the tunnel. Surface sprays alone do not reach the bees in the wood.

Wait, then plug. Once the galleries are quiet we return to plug each hole with a wooden dowel and caulk or putty. This follows the Penn State and University of Kentucky sequence: treat, then fill, then finish.

Paint or seal. The final step is yours or your painter's. Kentucky's fact sheet says carpenter bees usually will not tunnel into painted wood and that stains and preservatives are less reliable than painting.

Written 1-year guarantee. Carpenter bee treatment carries a 1-year written guarantee. If they reopen a treated board within a year, we come back at no charge.

Look at the abdomen. Kentucky's fact sheet says bumble bees usually have a hairy abdomen with black and yellow stripes, while the carpenter bee's abdomen is shiny and mostly bare. The other tell is where they go: bumble bees nest in an existing cavity, often underground in an abandoned rodent burrow, and carpenter bees tunnel into wood. A big black bee hovering at your fascia in April is a carpenter bee. One coming out of the ground by the shed is a bumble bee, and we leave those alone.

Paint the wood. Maryland Extension says carpenter bees are attracted to raw, unfinished, stained or weathered wood, and that well maintained painted wood is rarely attacked. Ohio State lists the softwoods they prefer, cedar, redwood, cypress, pine, and fir, which covers most Long Island trim and decking. Clemson notes that non-wood surfaces such as vinyl siding are not damaged, and NC State points to composite materials as an option for replacement boards.

Treatment timing matters too. Maryland's advice is to treat in spring just as the bees become active, or in late summer. Those are the two windows we work.