Carpenter bees and how to control them

The size of carpenter bees varies between approximately 16 and 25 millimeters. They are similar to bumblebees, but they are not the same. 

Bumblebees (genus Bombus ) nest on the ground, usually in abandoned rodent nests, and live in communities. Carpenter bees (genus Xylocopa ) are solitary burrowers that burrow into wood. They can be identified by looking at 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. Both species are considered beneficial insects because they are excellent pollinators. Therefore you should avoid deleting them unless absolutely necessary.

Carpenter bees live for about a year. Each new generation hatches in late summer, emerging from nests in August and September to grow, feed and pollinate flowers as they do so, before going into seclusion for hibernation. Those that survive the winter emerge in April and May to reproduce. The female carpenter bee digs a tunnel where she raises her offspring. In each brood chamber she stores food and lays one egg. After reproducing, the adult carpenter bees die off in July, leaving the new generation to continue the cycle when they emerge about a month later.

People generally encounter carpenter bees during April and May, when they emerge to breed. During the breeding season, male carpenter bees hover around nest openings, searching for receptive females. It can be a bit unsettling to be around them, as the males will also aggressively prowl around individuals who approach the nests. They can even fly right at you. Despite the aggressiveness they express, male carpenter bees cannot sting. Females do, but almost never do.

How to identify nests

Seeing a bee emerging from a hole in the ground or a wooden structure is a good indication that a carpenter bee nest is there. To be sure you have to look at the entry holes. A carpenter bee makes an entrance hole slightly larger than its body, about 13 millimeters in diameter. the bees make the first sections of the tunnel, between 2 and 5 centimeters deep, against the grain of the wood. The tunnel will then turn to the right and extend 4 to 6 inches in the direction of the wood grain. Carpenter bees usually remove their waste before entering their nest, so yellow spots are often seen on the surface of the wood, just below the entrance hole.

Although they burrow into wood, carpenter bees do not eat it like termites. Since their nest tunnels are short, they rarely cause serious structural damage. Because tunneling takes a lot of energy, a carpenter bee will often prefer renovating an old tunnel to making a new one. If carpenter bees are allowed to tunnel into the same structure year after year, the cumulative damage can be significant. 

How to control carpenter bees

Carpenter bees prefer to dig raw, unfinished wood. You can prevent carpenter bees from nesting by painting or varnishing the exterior of your home. But if they have already invaded the structure, you will need to use an insecticide to kill them. Many specialists recommend using aerosols or powdered insecticide, since they can reach the inside surface of the entrance holes. Apply the insecticide at dusk, when carpenter bees are least active. 

For the insecticide to be effective, the bees must come into contact with it when they crawl through the nest entrance hole. Apply the insecticidal dust in spring, just before the adults emerge to breed. Once you see the bees emerge wait a few days and fill the nest holes with putty. If you did not apply the insecticide before the adults emerged in spring, you will need to treat nests in spring and again in late summer when the next generation of adults feed. In fall, fill nest holes with steel wool, then seal with caulk, fiberglass, or asphalt.

Going to pest control specialists is a good alternative, especially if the pest is widespread as they have special tools that can reach the bottom of the holes. If you want to do it yourself, any insecticide to kill flying insects should be effective. If you prefer to use a natural product, you may consider boric acid, diatomaceous earth, or citrus spray. You can also contact an official body to find out which insecticides are effective and are allowed to be used to control carpenter bees.

Sources

• _{Bamabara, Stephen and Waldvogel, Michael. Residential, Structural, and Community Pests. University of North Carolina. July 2009.}
• _{Houseman, Richard. Carpenter Bees . The University of Missouri Extension.} 
• _{Jacobs Sr., Steve. Carpenter Bees . Pennsylvania State University. January 2014}
• _{UC Davis staff. Carpenter Bees Management Guidelines . University of California. June 2014.}
• _{13 Home Remedies to Get Rid of Carpenter Bees 13 Home HomeRemedyHacks.com. January 27, 2015.}