Carpenter Bees: Carpenter bees suffer from a serious identity problem; they are often mistaken for bumble bees. They do look a lot like bumble bees, but there is a big difference in the biology and habits of these two groups of bees, which do not even belong to the same entomological family. One of the most easily observed physical differences is that the top of the abdomen of carpenter bees is slick and shiny, while bumble bees are covered with black, white, or yellow hairs.
Xylocopa virginica is the primary species of carpenter bee that occurs here in the state. The ‘white-faced’ males are hard to miss because of their habit of buzzing about, hovering in mid-air, and occasionally hovering in one’s face. Some people feel threatened by this behavior, but the males are harmless because they have no sting, and many of us can remember playing with ‘white-faced bumble bees’ as children.
The females do have a sting, but they are not aggressive, and do not sting unless forced to do so. It is very uncommon for someone to get stung by a carpenter bee. Females are easily distinguished from males because their face is solid black, while the males have the distinct white spot in the middle of the face. Females also behave differently than males. They don’t have time for the idle buzzing and aerial acrobatics of the males. They spend their time boring nesting galleries, collecting pollen and nectar to provision the gallery, and laying eggs.
Galleries, which are about ½ inch in diameter and may be up to two feet long, are most commonly made in unpainted softwood lumber. They especially prefer pine, cypress, and cedar, but will occasionally bore in other types of lumber.
Carpenter bees tend to congregate around favorable nesting locations, and females will reuse, and enlarge old galleries from year to year. Timbers can be weakened by the presence of multiple galleries, and galleries can also allow moisture to enter the wood and hasten decay. Consequently, carpenter bees can weaken the structural strength of buildings with exposed beams and rafters that are repeatedly attacked over many years. There are two generations per year, one in spring and one in fall, and carpenter bees overwinter as immature bees inside these galleries.
Painted or sealed wood is seldom attacked by carpenter bees, so painting or sealing the wood surface is the best long-term method of preventing this problem. Vinyl or aluminum siding works even better. However, there are situations where the rustic look of unpainted wood is preferred and situations where it may not be practical to paint the exposed beams and rafters in barns, storage sheds, etc. When using paint to prevent carpenter bee attack, it is important for the paint or sealant coat to be thick enough to totally cover the wood grain. The bees will readily bore through paint as long as they can still ‘feel’ the wood grain.
Unfortunately, there are no insecticide sprays that can simply be sprayed onto exposed wood surfaces to provide long-term control of carpenter bees. Carpenter bees do not eat wood, they just bore holes in it to make their nest galleries, and the relatively small surface area of treated wood female bees consume when boring nest holes is not usually enough to have much effect.
The most effective way to control carpenter bees with insecticides is to apply small amounts of insecticide dust directly into the galleries. This literally “gets ‘um coming and going.” Female bees are killed when they return to the gallery and newly hatched bees are killed when they emerge. Dusts work better and last longer than liquid or aerosol treatments because they remain in the gallery, where they will contact the bees, rather than soaking into the wood (some dusts provide up to 9 months of residual control). Don’t try to seal up the holes too soon after treating; wait until you are sure you have gotten control, then seal the holes and paint over the area (if the surface was painted to begin with). Because carpenter bees often reuse old galleries, just dusting the galleries and leaving them unsealed is the best way to deal with carpenter bees in unpainted wood (barns, sheds, cedar siding, etc.) By treating all open galleries that you can reach a couple of times per year, you can greatly reduce the carpenter bee population, though you will probably never get 100% control. But, if you are able to treat a high percentage of the galleries that are in use, you can reduce the overall population of carpenter bees around the property.
Two of the most commonly available dust products are Terro Ant Dust and Enforcer Fire Ant Killer, which contain deltamethrin and are labeled for control of bees and wasps. There are also other brands of deltamethrin dust (DeltaDust is the brand used by professional pest control companies), and dusts containing other active ingredients, available through local distributors, but read the label carefully to verify that the product is approved for the intended use. Drione dust, which contains pyrethrins + piperonyl butoxide + silica gel, is another effective dust option. Dust can be quickly and easily applied into galleries by the use of a bulb duster. However, bulb dusters may be difficult to find locally and may have to be specially ordered (there are several online suppliers—just search for “bulb duster”—can usually order the bulb duster and DeltaDust from the same site). One hazard associated with this means of control is that it may require the use of a ladder. Be careful if you use a ladder. Watch for electric lines and don’t fall!
Some companies sell “dust sticks” or pole-mounted dusting devices that can be used to inject dusts into overhead nest holes while standing safely on the ground. This is safer than being on a ladder, but it takes patience, persistence and good coordination to be able to direct the dust tip into a ½ inch hole that is 10 feet overhead.
What about the carpenter bee traps that catch bees that enter the hole in the trap? Well, these do catch some female carpenter bees, and every bee trapped is one less to bore holes in the house. For buildings with heavy carpenter bee pressure, use traps to supplement nest hole dusting efforts.
What about using a badminton racquet or airsoft airgun to zap carpenter bees as they are hovering around? While this can be an entertaining pastime, these are mostly males—notice the white face, and just killing a few males in this way likely won’t have much long-term effect.
But aren’t carpenter bees pollinators? Don’t we need to be protecting them, rather than killing them? Carpenter bees are indeed beneficial pollinators. But termites are also beneficial. As long as they stay out in the woods, termites play an important ecological role in helping recycle forest nutrients. It is only when they attack our homes and buildings that termites should be considered and treated as pests. The same is true for carpenter bees.
