Large carpenter bees (Xylocopa spp.), despite their ecological importance, should not be allowed to build nests on your home or outbuildings for any longer than one season. While they are less aggressive than other bee species, years of repeated carpenter bee nesting activity can result in damage to wooden structures. Furthermore, if a family member has a bee allergy, it can still be dangerous for them to enjoy the outdoors during the spring and summer. Even though carpenter bees are unlikely to sting, they can be provoked. A single sting can result in anaphylaxis, a reaction that includes hives, nausea, difficulty breathing, loss of consciousness, and sometimes even death.
If carpenter bees are nesting in trees, stumps, logs, or disused wooden buildings around the home, it’s best to let them be. They are native pollinators and should be protected whenever possible.
Here, we’ll cover carpenter bee identification, the damage they can cause, nesting behavior, repellents, and other control methods (including how to get rid of carpenter bees naturally), when to call professionals, things that probably won’t work, safety tips, and carpenter bee prevention.
In this article:
- Carpenter bee identification
- Carpenter bees on your property
- Methods to get rid of carpenter bees
- Natural carpenter bee repellents
- Products lethal to carpenter bees
- When to call a professional
- What might not or will not work
- Safety tips
- After treatment and prevention
Carpenter bee identification
There are nearly 500 Xylocopa species worldwide. Approximately 7 species are native to North America. Another genus of carpenter bees, the small carpenter bees (Ceratina spp.) nest in plant stems and are thus of little concern as a pest. As such, we will only cover large carpenter bees here.
What are carpenter bees?
Carpenter bees are members of the order Hymenoptera, along with wasps and ants. Bees and wasps alone account for around 20,000 Hymenoptera species.
Carpenter bees are large and round. They are approximately ½-1 inch long and are the largest native bees in the U.S., a distinction they share with bumble bee queens. They are often primarily black or dark blue, often with a hairy yellow thorax sporting a small bald patch on the back and a completely black, shiny abdomen. Males are differentiated from females by the presence of a white or yellow triangular marking on their faces.
Carpenter bees are solitary bees, meaning that females nest individually. Social bees (e.g., honey bees, bumble bees) nest in colonies of hundreds to thousands of individuals. The solitary carpenter bee females excavate individual tunnels in wood and primarily provision their eggs alone. Because they nest in wood, they are sometimes called “wood bees”. Some researchers consider them mildly social as they sometimes nest near their mothers and sisters (in the same gallery of branching tunnels) and some provision their sisters.
Carpenter bee activity
In April or May, carpenter bees emerge from hibernation. In some areas, this occurs as late as early June. Males arrive first and hover around nest holes, waiting for females. At this time, males are aggressive and territorial, attacking other male bees as well as dive-bombing people and other animals. However, male bees lack a stinger and are harmless. When females emerge, they either search for a suitable nesting site or begin clearing and enlarging the tunnel in which they overwintered. Female carpenter bees often use a previously constructed nest tunnel rather than beginning a new one. Males and females feed on nectar and pollen (and pollinate a wide variety of plants), mate, and the males die soon after. Once fertilized, the female carpenter bee prepares a substance called “bee bread”: a pellet of mixed pollen and nectar. She positions a pellet at the back end of her tunnel, lays an egg, then seals up the chamber with a mixture of chewed up wood and saliva. Next, she makes another pellet, lays another egg, and seals up the next cell. She continues this process, moving from the back of the tunnel towards the opening until she has constructed around six or seven egg chambers. The females don’t live long after laying eggs, typically dying off in July. A few days after they are laid, the eggs hatch into larvae. The larvae remain in their tunnel chambers, feeding on the bee bread before pupating into adults. Around August or September, these new adults emerge by chewing their way out of the nest cells. After a short period of feeding on nectar and pollen, they return to their natal tunnels to hibernate through the winter. The entire seasonal cycle, from emergence in the spring to the new generation’s emergence in late summer, lasts around 7 weeks. There is usually only one generation per year, but in some areas, there are two.
Signs of carpenter bee activity include yellowish streaks along the wall and piles of sawdust beneath round holes.
Carpenter bees vs. other bees
Aside from carpenter bees, bumble bees and honey bees are the most often encountered. They may seem very similar at first but they have some defining characteristics.
Carpenter bees can be confused with bumble bees due to their size and roundness. However, rather than being shiny and black, bumble bee abdomens are covered in furry black and yellow bands. Bumble bees have a corbicula, or pollen basket, on each of their hind legs, which carpenter bees lack. Carpenter bees are less aggressive than bumble bees and other social insects.
Carpenter bees and honey bees are quite different. Honey bees are smaller and less round than carpenter bees. They are also lighter colored (golden brown) and don’t have the shiny black abdomen characteristic of carpenter bees. Like bumble bees, honey bees also possess a corbicula. While honey bees can only sting once (the act of stinging kills them), carpenter bees can sting repeatedly, though they do exhibit less defensive behavior than do honey bees.
Carpenter bees on your property
So, what kind of neighbors are carpenter bees? We’ll cover the damage and risks of having carpenter bees on your property, the process of excavating a nest, and what’s going on inside.
First, it should be noted that carpenter bees are important pollinators. Like bumble bees, they pollinate early in the morning and perform a special type of pollination called buzz pollination that allows them to pollinate some plants (e.g., tomatoes, eggplant) that other bees and wasps can’t. Thus, they serve an important role in the natural environment and your garden.
Damage and risks
Though a single season of carpenter bee activity is unlikely to cause much structural damage, repeated nesting by multiple generations of bees will.
Each successive generation of nesting females that uses the same nest site enlarges the original tunnel and adds new tunnels that branch off the main passage. Nest tunnels can reach up to 10 feet long.
Over time, this weakens the wood. Furthermore, the openings allow water permeation, causing the wood to rot. Occasionally, carpenter bee nests can attract woodpeckers, which further damage wood to reach the larvae inside.
Carpenter bees also cause aesthetic damage. In addition to the unsightly holes, they defecate on the surface of the wood. This leaves yellowish stains that eventually mold and turn black.
Carpenter bees’ nests
How females start nests
A female carpenter bee begins a nest by scraping out a small, round dent in the wood’s surface with her mandibles (jaws). She enlarges the dent into a nearly perfectly round hole approximately ½-inch in diameter. After digging into the wood about ½ inch, she makes a 90o turn and bores a tunnel in the direction of the wood grain. Carpenter bees excavate about 1.5 cm per week until the tunnel reaches a length of 6 to 12 inches.
Unlike honey bees and bumble bees, carpenter bees are solitary, so there is no caste system within a nest. The females create individual tunnels with only their eggs to provision. Sometimes, daughters live in the same tunnel network as their mother and have been known to provision other immature bees in the nest. However, this is only a rudimentary social structure. There is no hierarchy within carpenter bee tunnels.
Carpenter bees target soft, weathered woods, including dead limbs, stumps, and trunks as well as unpainted structural woods. Different carpenter bee species in eastern and western North America differ in the wood they prefer to nest in. Eastern species are drawn to softwoods such as cedar, cypress, fir, and pine. Western species prefer hardwoods, such as oak and eucalyptus. Species on both sides of the continent like redwood. On and around homes, carpenter bees can often be found nesting in decks, eaves, fascia boards, rafters, roof shingles, siding, outdoor furniture, and fence posts. Cracks and nail holes are particularly attractive because the work has already been started.
Less preferred targets
Carpenter bees don’t attack painted wood and are unlikely to bore into live, fresh, or pressure-treated wood or wood that still has bark on it.
Methods to get rid of carpenter bees
Getting rid of carpenter bees is difficult. It’s easier to control a new nest than one that has been established and reused for years. For a relatively new tunnel, vacuuming may be enough for carpenter bee removal. However, this is considered a very dangerous method that may well be ineffective. In all likelihood, you’ll end up with several angry bees in a good position to sting you. If you choose this method, find the entrance hole(s) during the day and return in the evening when the bees are less active. Use a vacuum with a long hose so you don’t need to approach too closely. Seal and throw away the bag once you have sucked the bees out of their tunnel. If you have a bagless vacuum, we recommend that you don’t use this method.
Another mechanical control method is to simply block them in or out by plugging the holes. In this case, it’s best to either wait until the female is out foraging or apply a barrier in the evening. Because they only chew wood, filling the holes with caulk, cement, plastic, expanding spray foam, wood putty, or wool will reduce the chances that a female will bore her way back in through the barrier.
A piece of wooden dowel covered in a sealant like glue or putty will also work. Metal coverings are even better. However, this will only work if you also apply repellents around the rest of the wood’s surface. Finding her hole plugged, a female carpenter bee is likely to make a new entrance. Similarly, if a bee finds itself trapped within its tunnel, it will just chew its way out somewhere else. If in doubt, professionals can apply chemically treated barriers or chemical repellents that will be both effective and long-lasting.
Natural carpenter bee repellents
To get rid of carpenter bees without killing them, there are some natural scents that they don’t like.
- Citrus is one such scent. You can either use a citrus oil spray or make your own by boiling citrus peels in water and pouring the mixture into a spray bottle.
- Tea tree oil is also a natural carpenter bee repellent that you can mix into water in a spray bottle.
- Spraying or sprinkling almond oil or almond essence where you’ve noticed carpenter bee activity can also help.
- A solution of citronella (1/2 ounce), jojoba oil (1/8 ounce), lavender oil (1/4 ounce), pennyroyal oil (1/4 ounce), and tea tree oil (1/8 ounce) also works as a carpenter bee spray.
- To increase the potency, add 16 ounces of plain vodka. Garlic marinated in cooking oil (let sit for a few days) is another effective concoction to deter carpenter bees. If you mix it with white vinegar, it becomes a wood bee killer.
Keep in mind, however, that repellents are only a temporary solution. They have no residual (lasting) power and must be reapplied daily.
Products lethal to carpenter bees
In some cases, mechanical controls with a chemical assist won’t be enough and you’ll need to use a carpenter bee killer. Pesticides should always be a last resort. Remember that bees, including carpenter bees, provide a crucial service to us and the rest of the planet in the form of pollination. Once you’ve exhausted all other avenues, here are some lethal carpenter bee control methods, including natural products, traps, and synthetic insecticides.
If you’re not ready to go synthetic, you can use natural products to kill carpenter bees. Boric acid and diatomaceous earth are powders lethal to insects. Puff them into carpenter bee holes. Leave holes open for a few days for the bees to come back and get the dust on their bodies. Not only will it kill them directly, but they can spread it along the tunnel where other bees might brush against it.
- Boric acid kills insects by attacking the stomach and nervous system. It can kill plants and is slightly toxic to humans.
- Diatomaceous earth dehydrates insects, eventually killing them, and also has low toxicity to people.
- You can also mix one tablespoon of 99% rubbing alcohol, two teaspoons of apple cider vinegar, and 6 drops each of lavender essential oil and tea tree oil. Spray this mixture around places you’ve noticed carpenter bee activity. The alcohol and vinegar will kill the bees and the essential oils will act as repellents.
Carpenter bee traps
Commercial carpenter traps are available or you can make your own. Build a small wooden box (ideally out of one of the preferred woods mentioned above). Leave an opening on the bottom of the box for an upside-down clear plastic bottle. Attach the mouth of the bottle to the mouth of another clear plastic bottle so that it is suspended beneath the box. Drill ½-inch holes at an upward angle in each side of the box and hang it from your eaves. Carpenter bees will investigate the holes to see if the box provides a good nesting site. When they crawl in, the angle of the hole keeps it dark relative to the plastic bottle. Carpenter bees fly into the bottle in their search for an exit and become trapped. Deprived of food and water, the bees eventually die. Wood bee traps are only effective for small populations. If you have a larger infestation, you’re unlikely to trap enough for control.
You may have heard that carpenter bees are attracted to pheromones released by dead bees. However, this is only true in social bees and is restricted to the death of the queen.
Insecticides are very useful, but also dangerous. They are poisons, though they often have low toxicity for large mammals. Here, we’ll cover the three main types of insecticides for use on carpenter bees (foams, dusts, and sprays). For each carpenter bee treatment, you should wait a few days to a week before closing off the holes to allow as many females as possible to return and contact the insecticide. Apply insecticides early in the spring when the bees are first emerging or in the late summer when the next generation is coming out of their egg chambers (or both). Use as little as possible to avoid simply repelling the bees. This could cause them to start new holes nearby. Always spray or dust in the evening or when bees are out foraging.
You must spray or dust directly into an existing tunnel opening. Simply using insecticide as a protective layer on your wood surfaces is likely to lead to only limited success. Since carpenter bees don’t eat the wood, they may not receive a lethal dose during excavation.
The major ingredients in carpenter bee insecticides are pyrethroids such as bifenthrin, cyfluthrin, deltamethrin, esfenvalerate, lambda-cyhalothrin, permethrin, and resmethrin. Other ingredients to look for are carbaryl and imidacloprid. All of these carpenter bee insecticides are highly toxic to other bees as well and should be used with caution if bumble bees or honey bees are nearby.
Pyrethroids generally kill by attacking insects’ nervous systems, leading to muscle spasms, paralysis, and death. Cyfluthrin and esfenvalerate additionally poison the stomach when ingested. Most pyrethroids have low toxicity to people and pets, but cyfluthrin and the related beta-cyfluthrin can have adverse effects on humans and other mammals. Permethrin is only slightly toxic to humans and dogs, but moderately toxic to cats. Nearly all pyrethroids are highly toxic to aquatic animals and slightly to moderately toxic to birds.
Carbaryl targets the nervous system, is moderately toxic to mammals, only slightly toxic to birds, and highly toxic to aquatic life. Imidacloprid is not a contact insecticide; it must be ingested. Like other insecticides, it targets the nervous system. It is moderately toxic to mammals and only slightly toxic to birds and fish.
Foams are sprays that expand after they are expelled from their container. Use a foam insecticide with an applicator to spray directly into the hole. They are good for carpenter bee nests because they expand to fill the branches within the tunnel. This increases the number of adult bees, larval bees, and eggs that they will directly contact. However, it will serve as a plug, effectively cutting off the nest from females returning from foraging. These bees may be able to start over again nearby.
Dusts are powdered insecticides. They are most effective when puffed directly into carpenter bee holes. Some consider them more effective than liquid insecticides, though both dusts and liquids are recommended over foams. Some dusts have high residual power (months).
Aerosol sprays are safer and easier to use than other types. Any wasp, hornet, and/or bee aerosol will work. Like foams, they should be sprayed directly into the tunnel entrance, a task made easier with injectable applicators. It’s recommended not to just spray individual bees; it’s time consuming, dangerous, and you’d have the same luck with a flyswatter. Sprays have residual activity up to about 4 weeks, so may need to be reapplied.
When to call a professional
In some cases, a carpenter bee problem is too difficult to handle on your own. Perhaps you can’t easily access the tunnel entrances, you’re uncomfortable approaching close enough to spray or dust, or you’re allergic to bees. Those with allergies should always seek professional help for bee and wasp control. The amount you save through DIY doesn’t make up for epinephrine injector prices or a trip to the emergency room. Carpenter bee exterminators come armed with extensive knowledge, years of experience, heavy-duty protective gear, and control equipment, and often pesticides regular consumers can’t get.
What might not or will not work
In addition to effective treatments, you may run across some less effective to ineffective advice. We’ll cover some of these but check multiple sources to confirm any methods you find during your research.
- Don’t just plug the holes without treating them first. This goes for covering them with plastic and hoping the bees bake to death inside. The bees will simply chew a new hole. Similarly, plugging holes and painting the entire wood surface without insecticide treatment won’t work. Any bees stuck inside the tunnels will still chew through the painted wood to get out.
- Applying pesticides to the area around an entrance hole won’t kill the bees that live inside and might end up damaging your wood surfaces. Don’t over-apply. You risk repelling the bees from their original entrance and pushing them to start a new hole nearby. It might be tempting to preemptively spray all your wooden surfaces with pesticides as a protective layer. However, this is dangerous to you, your family, your pets, and any nearby wildlife, would require an impractically large amount of insecticides, and you would need to reapply at regular intervals to keep up the protection.
- Don’t squirt individual bees that you see hovering around. They are probably males, so you won’t control the bees tunneling into your house and it’s both time-consuming and dangerous.
- Vacuuming is a less effective method than others detailed here. Furthermore, disposing of or relocating the bees inside your vacuum can be just as dangerous as sucking them up in the first place.
No matter how you choose to deal with carpenter bees, always be careful around their nesting areas. While they’re not aggressive, they can be provoked.
Furthermore, if you opt to treat with insecticides, you must be careful not to inhale, ingest, or otherwise contact them.
- To avoid stings, apply insecticides at night or when the females are out foraging. If they fall out of the tunnel while you’re spraying, they might sting. Even if you treat at night, always be prepared for bees to exit the hole when you spray. If you’re treating a nest above your head and you’re on a ladder, you don’t want to be startled into losing your balance.
- When applying insecticides at night, use a flashlight covered with clear red plastic (cellophane works). Bees can’t see the color red, so you can illuminate the nest without disturbing them.
- If you choose to spray during the day, spray any bees flying around the tunnel entrance first.
- To avoid pesticide exposure, read and follow all instructions. Always store them in their original containers and keep them out of reach of children and pets.
- During treatment, keep the insecticides from drifting into nearby wild habitats.
- If you’re treating an overhead nest, it’s easy for the poison to fall down into your face.
- Always position yourself upwind of the treatment area. Try not to breathe it in or get it on your clothes or skin.
- When you’ve finished a container of an insecticide, dispose of it promptly, safely, and properly.
- For overall safety, wear long sleeves, long pants, closed-toed shoes, gloves, goggles, and a dust mask.
- Take a shower and wash your clothing (not with your regular load) immediately after nest treatment.
After treatment and prevention
What to do after treatment
A few days to a week after treatment, seal up the entrance holes. If you want to ensure they won’t come back, paint or varnish the wood after plugging the holes. If an infestation was particularly bad, you may need to remove the affected part and replace it.
Carpenter bee prevention
One of the most important steps in any pest control program is prevention. If you don’t want carpenter bees on your property, it can be easier to keep them out than get rid of them after they’re established. It’s especially difficult to eradicate a long-standing population with a network of tunnels. Prevention also means you don’t have to kill anything. Here, we’ll cover how to keep carpenter bees away from your home and outbuildings.
Carpenter bees avoid painted wood. One of the easiest ways to prevent them from nesting in your house is to paint any exposed wood. Keep your wooden structures in good condition. Replace any old or weathered boards. Be sure to fill in or cover nail holes or cracks. Use pressure-treated wood or wood with a metallic salt preservative. When possible, use hardwoods. Opt for vinyl or aluminum siding or siding covers. Composite sidings, such as masonry or cement board, are also effective. In addition to siding, you can replace wooden railings and fence posts with PVC.
If you can’t replace wooden structures and parts, paint, or otherwise cover your wooden surfaces for financial or aesthetic reasons, spray them with repellents at the beginning of the season. Another method with some success is to make a lot of noise during the early spring when carpenter bee females are out looking for nesting sites. This may keep them away from your home, though it’s unclear why this method works and it may not work for everyone.
Having carpenter bees nesting near your home can be a good thing. They are an important pollinator and not an aggressive type of bee. However, they have the annoying habit of drilling into homes and other wooden structures to establish a nest of branching tunnels. While a single season of carpenter bee activity is generally not enough to cause serious damage, multiple years of continued habitation can weaken the wooden parts of your home. Carpenter bee nests on homes or oft-used outbuildings can be of aesthetic and financial concern and should be eradicated.
In this article, we’ve covered how to get rid of wood bees, from mechanical control (vacuuming, plugging entrance holes and applying insecticides or repellents), to natural repellents and natural and synthetic insecticides. We have further given advice on when to reach out to professionals, what methods don’t work, safety tips, and how to prevent future infestations. Good luck!