Don’t you just love the glorious profusion of new life as gardens and landscapes wake up from their long sleep? The days get longer, flowers and trees blossom, and birds, butterflies, and cute critters return from their winter respite. And, oh yes… so do the pests. Pests like carpenter bees. With their giveaway, dime-sized holes that they chew in your wooden structures to build nests. We link to vendors to help you find relevant products. If you buy from one of our links, we may earn a commission. But they do like to nest in dead wood. And structural components like beams, eaves, posts, and siding are all fair game. To be fair, they don’t actually eat the wood and won’t devour a building like carpenter ants or termites do. And damage is usually minor and cosmetic in nature. But if left unchecked, over time the damage can worsen and lead to more serious problems such as decay, moisture retention, and rot.
So, if you think carpenter bees have set up shop in your shop, please read on. We have everything you need to identify a possible infestation and how to be rid of it – naturally if possible, but we dish on chemical warfare too!
Identification and Biology
Carpenter, or borer bees, are in the genus Xylocopa of the Apidae family, with hundreds of species in several subgenera found around the world. They’re aptly named for their nesting behavior of burrowing into dead wood to establish tunnels in order to lay eggs.
Featuring short mouthparts, carpenters are important pollinators on open-faced or shallow flowers and those that form lids. And for some species, like the maypop (Passiflora incarnata) and sea rose (Orphium frutescens), they’re the only pollinator. Naturally docile, males don’t have stingers – although they will hover close to animals and people that approach nest sites. And the females only sting when aggressively provoked or handled. Xylocopa are most active in the period of mid-late spring to early summer when they’re looking for suitable mates and nesting sites. Measuring 1/2 to 1 inch in length, there are numerous variations to their colorings, many with black and yellow or black and orange markings. They have shiny, smooth abdomens, black in color with females often displaying metallic tones. And there are some that have iridescent wings, as well as species with bright blue or chartreuse body hair.
Unlike many species that live in large colonies, carpenters are not social insects. After mating, males will stick around to protect the nest. But it’s a solitary female that constructs the nest, forming long tunnels into which she lays the eggs. Once laid, eggs go through another two stages of development, larva and pupa, before they emerge as adults approximately seven weeks later. In several species, females may live near their own daughters or sisters, creating a small family social group. Many species are similar in size and shape to bumblebees, and the two are often confused. And they’re often misidentified as ground-burrowing species as well.
Predators
Natural predators include badgers, mantises, predatory flies, and some birds such as bee-eaters, shrikes, and woodpeckers. Unfortunately, woodpeckers will cause more damage by drilling into the wood beside nests to get at the grubs.
Nesting and Favored Habitats
Carpenter bees don’t actually eat wood. The females bore holes by using their mandibles as a rasp against the wood while vigorously vibrating their bodies.
Each nest features a single entrance that usually spreads to connecting tunnels, called cells – these are the nurseries where eggs are deposited. A new gallery measures around 4-6 inches in length, but those reused over several years can be 10 feet long! Their favorite building material is soft, unpainted, and aged wood, although there are species that prefer hard woods. And any wooden structure is suitable. Arbors, decks, eaves, fascia boards, gates, patio furniture, pergolas, porch ceilings, posts, siding, and window trim are all suitable sites. Once the cell is ready, the mother provisions each one with a platform of pollen and nectar, called a pollen loaf, upon which a single egg is laid. She then partitions the cell with a wall of chewed wood pulp. Larvae will feed on the pollen loaf until they emerge from the nest.
Adult carpenters will often overwinter in their original tunnels or find abandoned ones, which they stock with pollen to survive the cold. The ones that survive the winter will emerge in spring to mate, with both the males and females dying after mating and laying eggs.
How to Identify Nesting Sites
The most obvious signs of an infestation are the round, half-inch holes that carpenters bore into wood as an entry point.
And if you spot several males hovering in one spot, it’s a good indication that a female, and her nest, are usually nearby. In addition to the entry holes, there may also be a small pile of fresh sawdust outside the hole, scraping sounds from within the wood, or a fan-shaped stain below the opening.
Organic and Chemical Control Methods
Here are a few natural methods to make your home less attractive as a nesting site:
9. Insecticide Spray
Deterring carpenters with natural solutions is the preferred method, but if you must pull out the big guns, here’s our first suggestion: Typically used to provide nesting sites for garden-friendly pollinators like mason bees, hotels may provide an alternate site for females looking to nest. JCs Wildlife Small Poly Lumber Bee House
2. Citrus Oil
Citrus oil is a safe, natural repellent that carpenter bees dislike, and you can easily make your own at home. Cut up a selection of peels from a variety of citrus fruits, place in a pan, and cover with water. Bring to a boil, then reduce heat and simmer for 10 minutes. Remove from heat, allow to cool, then strain and pour the water into a spray bottle. Douse the nest with your spray and reapply until all the females have relocated, then repair and paint the wood as described in the next tip. I haven’t tried citrus oil for insects, but it is my personal favorite to prevent deer from grazing in the garden. And it repels rodents as well. Pure Cold Pressed Orange Oil Concentrate, 32 oz. (D-Limonene)
3. Dress Exposed Wood
It’s easier to be proactive in discouraging carpenters than it is to react to their destructive burrowing. To dissuade them from starting nests, paint all exposed surfaces with a primer and two coats of exterior paint. Stains and varnishes also offer some protection but are less effective than paint. Before you paint, fill all cracks, nail holes, and splinters with caulk, putty, or wood filler as any existing damage provides an appealing point to start a nest.
4. Fill Abandoned Holes
As overwintering adults emerge in spring and new ones come out in late summer, stuff the entrances with caulk, a dowel, wadded aluminum foil, spray foam insulation, or steel wool. Smooth the surface and paint as outlined above.
5. Hang a Decoy Wasp Nest
Carpenter bees will avoid nesting in the same area as wasps. To mimic the shape and size of a wasp nest, stuff a brown paper bag with lightweight material such as moss, paper, or plastic bags. Tie off the open end with a length of string and hang it in the area you want to protect. Keep in mind that this only works to deter them from building new nests – it won’t keep insects away from an existing nest in the area. Waspinator, Set of 3
6. Lay a Trap
An easy method to get rid of your infestation is to place a trap near the nest. A trap consists of a wooden top with angled holes drilled into it and a plastic container or jar attached to the bottom. Because of the angle of the holes, the only light source comes from the bottom. The bees enter the hole, head for the light in the jar, then can’t get back out. Traps should be located directly above an active nest. It may take a while for the trap to work, but once one or two have entered and released pheromones, others will be attracted to the site as well. Original B Brothers-Carpenter Bee Trap
7. Turn Up the Tunes
It turns out that bees communicate through vibroacoustics, and they can “hear” low frequency sounds of up to 500 Hz. This makes them sensitive to vibrations, and they can be encouraged to vacate nests by playing loud music close by. Choose music with a deep, reverberating bass line (a bass guitar has low frequencies) and place the speaker right against the wall beside their location – then crank up the volume! Once the females have vacated, plug the hole and paint.
8. Use a Tennis Racket
In the spring when bees are most actively seeking nesting sites, you can dispatch flying critters with a good backhand. Use an old badminton, tennis, or squash racket and patrol on a sunny day, giving a smack to those eyeing up your wood. Products like flying insect sprays will kill the queen and her eggs. Use a liquid or aerosol product with an extension tube and apply directly into the hole. Application should be done at night while they’re resting, or in early spring before they emerge from hibernation. If you choose this method, always read and follow label instructions and wear protective gear as needed.
10. Carburetor Cleaner and WD40
An alternative to insecticides is to use an aerosol such as carburetor cleaner or WD40. These petroleum-based products will effectively kill any insects. Use a spray with an extension tube to get into the tunnels.
11. Petroleum
A little gasoline in a spray bottle can be an effective homemade insecticide as well. Spray the entrance regularly until there’s no more activity. This is a technique likely used by your grandparents in the past. We don’t recommend it and would choose another method. It may not even be (bee?) legal with the stricter environmental laws that are in place today in many areas. Of course, petroleum and petroleum-based products are highly flammable and should never be used near an open flame or an ignition source. When finished, be sure to label your spray bottle to avoid accidental misuse, and don’t store in the house or in high temperature environments such as outbuildings without air conditions. We are not responsible for accidents or Darwin Award winners. Use at your own risk! With all chemical applications, avoid getting the products on your skin or inhaling the fumes. Wear eye protection, a respirator, and gloves when applying chemical products. Keep up a regime of repairing any damaged wooden surfaces, repair holes on a regular basis, and paint surfaces.
If you do have an existing infestation, try one of the solutions above or hire a pest control expert to do it for you. But please remember that these are gentle little creatures performing a vital service for our well-being! If possible, lure them out and tell them to buzz off before resorting to killing them. Do you folks have any favorite solutions for getting rid of these flying insects? Shoot us a line in the comments below. And be sure to check our guides on garden diseases and insects for other pest solutions, or buzz on over to these articles to increase your knowledge:
Integrated Pest Management: What Is It, and How to Use It? 23 Beneficial Insects and Other Creepy Crawlies That Your Garden Will Love Extend the Season and Keep Pests Out with Floating Row Covers
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