As unaggressive creatures, female carpenter bees only sting when seriously provoked or handled. Male eastern carpenter bees often hover around the openings to nests. Although the insects may appear aggressive to humans, the bees usually guard against other insects and care little about people. Still, spotting the large bees lingering around wood structures is an indication of carpenter bee activity or infestation. Additionally, homeowners may notice accumulations of pulverized wood on the ground below nest entrances.
As with most bee species, eastern carpenter bees are ecologically important. While pest control specialists may be called in to handle infestations with pesticides, killing the bees is strongly discouraged. Instead, homeowners should consider painting or varnishing external wood to deter carpenter bees, as the insects prefer untreated wood surfaces.
Another useful strategy for managing eastern carpenter bees involves purposely placing slabs of wood, which are ideal for burrowing, away from the home to give the insects a more suitable nesting option than household structures.
Eastern carpenter bees create nests by burrowing into wooden doors, windowsills, roof eaves, shingles, railings, telephone poles, wooden lawn furniture, decks, bridges, or any wood greater than 50 mm thick provides suitable space for the bee.
Eastern carpenter bees demonstrate a preference for coniferous wood and are primarily associated with forests in the United States and Canada. The bees also prefer surfaces without paint or varnish. Excavated galleries are an average of 10 to 15 cm long but may extend up to three metres in length with repeated use and when several females are nesting at the same time.
Unlike termites, eastern carpenter bees do not eat wood as they excavate tunnels. Instead, adults survive off the nectar of many different flowers. Although the insects contribute to the pollination of many flower species, eastern carpenter bees often bite into the bases of flowers and steal the nutrients without pollinating.
Adult males and females overwinter in wood tunnels and emerge in the spring to mate. After creating new space for eggs in existing burrows, females stock the chambers with bee bread, deposit an egg, and seal off each chamber. Typically, eastern carpenter bees produce six to eight eggs at a time.
The insect spends an average of 2 days as an egg, 15 days as a larva, 4 days in a prepupal stage, and 15 days as a pupa. Carpenter bees naturally nest in soft, old trees or even reed-like plants with soft, pithy interiors.
But they don't discriminate against inviting wood that happens to be part of your home. Unlike termites , carpenter bees do not eat wood. The damage they cause comes from tunneling into wood to create nesting chambers.
The bees bore entry holes about 1 inch deep into their targeted structure. Once inside wood, the tunneling bees branch out to create perpendicular tunnels about 4 to 6 inches long.
A female carpenter bee creates about six to eight of these chambers, where it will lay its eggs. Over many years, carpenter bee galleries can expand from several inches up to 10 feet in length.
Eastern carpenter bees are easily distinguished from common honey bees, but they're often confused with bumble bees. Their woolly abdomens have bands of golden yellow to brown. At up to 1 inch long, carpenter bees and bumble bees are two of the largest native bees in the United States. While both can have black and yellow hairs, Eastern carpenter bees have shiny black abdomens.
Bumble bee abdomens are covered with yellow and black hairs. These three types of bees are also very different in their habits. When they invade homes, they typically inhabit attics or cavities between walls.
These groups can number in the tens of thousands. Bumble bees are also social bees, but they live in small colonies and nest in the ground. Typically nonaggressive, they stay focused on flowers, not houses or people. Carpenter bees are not social bees; they live more solitary lives. However, small groups of related bees stay together and remain in the same area for generations. Once they have paired and mated the female bee drills into a suitable site while the male stays nearby to ward off intruders.
Male carpenter bees often frighten people with their aggressive behavior but since they have no stinger they are essentially harmless. Females have a stinger but only use it if molested. Once the initial hole is drilled through the surface, the bee will make a turn and excavate a tunnel along the grain of the wood.
This tunnel, which may run for several inches, becomes the cavity where the female deposits her eggs. Several eggs are laid in individual chambers separated by plugs of pollen on which the larvae feed until they emerge as adults during the summer months.
In addition to making new holes, carpenter bees also enlarge old tunnels. If left unattended for several years, serious damage to a wood member may result. In late fall activity may again be seen as both male and female carpenter bees clean out old nest cavities where they stay over winter.
Since carpenter bees tend to migrate back to the same area from which they emerged, it is important to implement some control measures in order to prevent logs and wood members from becoming riddled by these bees. Although carpenter bees prefer bare wood or distressed wood, they will attack wood that is stained. Painted wood surfaces, on the other hand, are rarely attacked since the bees must see or feel the grain of the wood in order to recognize it as wood. One of the most effective measures for preventing extensive carpenter bee damage is to fill old or empty holes with Energy Seal.
Carpenter bees are attracted to existing holes. Be sure to treat the hole before you fill it since live adult bees will drill right through the caulk on their way out. One way to keep carpenter bees from drilling into wood is by spraying pesticides that contain either cypermethrin, deltamethrin, or bifenthrin Ortho Home Defense Max onto wood surfaces.
When it comes to carpenter bees, these products act more as repellants than contact poisons. However, the effectiveness of these applications is only about three to four weeks, so the treatment will have to be repeated every so often.
Pesticides should only be used during the periods of peak activity in the spring and perhaps again in late fall. Be sure to follow label directions and read and understand any precautions that must be taken when using these products.
A few years ago we requested information about the effect of our gloss topcoat on reducing carpenter bee activity via survey. Out of over 20 responses by letter, phone and e-mail, only two reported any penetration of the gloss topcoat by carpenter bees. One home went from 20 to 30 holes the previous year down to 2 this past year and the other went from over 20 holes to 4 holes.
This confirms our suspicion that the Lifeline Advance Gloss exterior topcoat appears to provide a finish to the wood that carpenter bees do not find very attractive. That is not saying that the gloss finish repels carpenter bees. It does not. Although bees would occasionally land on the gloss topcoat, they just did not drill through it.
So why is that?
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