People often mistake carpenter bees for bumblebees, which look quite similar. Bumblebees nest in the ground, usually in abandoned rodent nests, and live in social communities.
Carpenter bees are solitary bees that burrow into wood. If you see a bee that looks like a bumblebee emerging from a hole in your porch, it's a carpenter bee, not a bumblebee. You can differentiate the two by examining the upper side of the abdomen. If it's shiny and hairless, it's a carpenter bee. A bumblebee, by contrast, has a hairy abdomen. Carpenter bees usually spend the cold months tucked inside their empty nest tunnels, protected from freezing temperatures and winter weather. In spring, they emerge ready to mate. By late summer, the young emerge as adults.
Because carpenter bees are beneficial insects, you should only eliminate them when necessary. Most people encounter carpenter bees during April and May, when they've just emerged to mate. During this time, male carpenter bees tend to hover around nest openings, looking for receptive females. It can be rather unnerving being around them, as the males will also hover aggressively around people who approach the nests. They may even fly right into you. Despite this tough act, male carpenter bees cannot sting. They are completely harmless. Female carpenter bees can sting, but almost never do. So carpenter bees pose almost no threat to people at all.
Obviously, if you observe carpenter bees coming and going from holes in your fascia board, deck posts, or other wood structures, that's a sure sign that those holes are carpenter bee nests. If you haven't seen bees, but suspect they may be burrowing in a fence or other structure, look at the entrance holes. A carpenter bee makes an entrance hole slightly bigger than her body. The first inch or two of the tunnel is usually made against the wood grain. The bee will then make a right turn and extend the tunnel another 4-6 inches in the direction of the wood grain. You might see yellow stains on the surface of the wood, just below the entrance hole. Though they burrow into wood, carpenter bees don't eat wood like termites. Since their nest tunnels are limited in size, they rarely do serious structural damage.
However, a female carpenter bee will often prefer to refurbish an old tunnel to digging a new one. If carpenter bees are allowed to tunnel in the same structure year after year, the cumulative damage could be significant. When it comes to carpenter bees, your best defense is a good offense.
Carpenter bees prefer to excavate untreated, unfinished wood. You can discourage and prevent carpenter bees from nesting in a wood structure by painting or varnishing the lumber. If carpenter bees are already a problem, you will need to use an insecticidal dust to treat the nests. Insecticidal dusts are usually applied with a puffer that allows you to coat the interior surface of the entrance holes with the insecticide using a gentle burst of air.
For the insecticide to work, the bees much come in contact with it as they crawl through the entrance hole of the nest. The appropriate insecticide must be applied in the spring, just before adults emerge to mate. Once you see the bees emerge, wait a few days before filling in the nest holes with wood putty or filler. Now is the ideal time to apply the insecticide because the spring adults are emerging now. It is a good idea to treat the nests twice once in the spring, and again in late summer, when the next generation of adults is foraging. Because bees will be active during the day, it's best to apply the pesticide at dust dark or at night. This will reduce your chances of being stung by females trying to defend their nests. In the fall, seal the nest holes with putty or filler. For assistance getting rid of carpenter bees, contact EHS Pest Control in Norwood.