The large bomber-like Carpenter bees can make you leap off your comfortable chaise lounge with their aggressive attitudes. But, fear not for your safety because the males, who do all the major buzzing, lack a stinger. However, it's not the sting of the Carpenter bee that you should be concerned with. It's their craftsman-like skill at peppering your house with holes used for nesting. One or two bees cannot do appreciable amounts of damage. But, ignore them and their ranks swell over time. That's when fence posts start looking like Swiss cheese.
Here's a primer on how to stop these drilling dynamos. Locate the holes. That should be pretty easy. After dark on a cool night, dust the holes with an insecticide labeled for Carpenter bees such as Tempo 1% dust. Do not seal up the holes. You want the adults to move in and out of the treated nesting holes, spreading the insecticide to assure that you kill off as many as possible. After all bee activity has stopped you can caulk the holes closed. Warning: The males may not have stingers, but the females sure do and they will use them to defend their nests. So, take proper precautions.
To prevent further activity make sure the wood under attack is painted or varnished. This is supposed to stop bee-boring activities. Some bees have not been informed of this preventative step, however, because homeowners often report that the bees continue to drill through the painted surfaces. If this occurs, pull out the big guns and treat the wood with an insecticide that contains the active ingredient cypermethrin. I like Demon WP for this job. You can find it in some Raid Ant and Roach products or you might be able to purchase it from one of many local pest control firms. Just be sure to carefully read the label and follow the instructions exactly.
If fighting Carpenter bees is not your forte, I would suggest you get a pest control professional to do the dirty work. It's not very expensive and it sure beats falling off a ladder in the middle of the night.