Carpenter Bees

Source(s): Maxcy P. Nolan, Former Extension Entomologist, College of Agricultural and Environmental Sciences.


The carpenter bee, Xylocopa virginica (Linnaeus), normally attracts quite a bit of attention in Georgia in late spring and early summer. Since it closely resembles the bumble bee, is quite large and attacks wood around homes, it can become an important household and structural pest.

APPEARANCE

Adult carpenter bees are large, one inch or slightly longer, robust insects. They are blackish in color and possess yellowish hairs mostly on the thorax. The abdomen is shiny black and is bare of hairs on top. This helps distinguish carpenter bees from bumble bees which are similar in size and coloration but bumble bees have yellowish hairs on top of their abdomen.

Carpenter bee eggs, larvae and pupae are seldom seen since they are out of sight in cells within galleries constructed in wood. When wood containing carpenter bees is opened to expose the immature, larvae are legless, white grubs and pupae resemble adults.

DAMAGE

Carpenter bees burrow into the exposed dry wood of buildings, telephone poles, fence posts, etc. causing an unsightly appearance to the wood and structural weakness. They usually choose wood that is soft and easy to work. They seem to particularly prefer California redwood, cypress, cedar, white pine and southern yellow pine. Other woods, even seasoned hardwoods, may be attacked if they have been softened by being unprotected and exposed to the weather for extended periods of time. Bare wood is preferred. Carpenter bees usually avoid well-painted wood and wood with bark on it. Wood with a stain or light coat of paint can be attacked. Also, wood that has been lightly pressure treated with metallic salts for above ground use, such as for decks, could become infested.

Female carpenter bees use their mandibles to bore 1/2 inch round holes into wood. About one inch of gallery is constructed every 6 days. Galleries normally run with the grain for 4 to 12 inches or even further when old galleries are extended.

Female carpenter bees seldom sting but when disturbed or handled they can inflict a painful sting. Male carpenter bees cannot sting but they often become aggressive and frighten people when they fly about their heads.

BIOLOGY AND HABITS

In the late spring and early summer, adult carpenter bees emerge from protected overwintering sites such as old nest galleries. These fertilized females soon begin boring into susceptible wood. After a gallery has been constructed, an egg is deposited with a mass of pollen and nectar. Then the egg with provisions is sealed off with a plug of wood pulp and saliva. The process is continued at the rate of one cell each day until approximately six cells are constructed. Adults then soon die. The larval period extends 30-45 days and the pupal period 14 days. Development form egg to adult requires 5 to 7 weeks or longer depending on temperatures.

CONTROL

There are at least three methods that could be used to control carpenter bees: 1. Aerosol treatments of insecticides applied directly to adult carpenter bees. 2. Residual surface and gallery treatments with insecticides and 3. Preventive treatments such as painting wood with thick coats of oil based or latex paints.

1. Aerosol insecticide sprays labeled for use to control flying insects and bees can be applied directly to carpenter bees. Care should be taken to prevent being stung. The oil based carrier and the insecticide will kill carpenter bees if applied directly to them. A few aerosols are available which have long range capabilities. These could be effective and safer to use than conventional aerosol sprays.

2. Residual applications of insecticides such as permethrin and cyfluthrin sprays can be applied to outdoor wooden surfaces which are being attacked by carpenter bees. An unsightly insecticide deposit could occur on treated wood so care should be taken. Nests or galleries can be treated directly with these insecticides or with others such as carbaryl or deltamethrin dusts that are labeled for carpenter bee control. Carpenter bees will be controlled when they contact the residual insecticide deposit.

Several days following treatment, after carpenter bee activity has ceased, holes can be plugged with dowel rods, plastic wood or with other suitable materials. If carpenter bees continue to attack the wood, additional residual insecticide treatments may be required at weekly or twice weekly intervals.

3. Wood which has been recently painted with oil based or latex paint will not normally be attacked by carpenter bees. Pressure treated wood is often resistant to attacks until it has weather for several years.

If you are looking for organic controls, there are only a couple of options which you can use. Boric acid can be used to control carpenter bees by placing this powder in the area or in the holes they make. Secondly, spraying pyrethrins can be effective, these chemicals are derived from chrysanthemums and are generally not considered to be dangerous.

Professional pest control operators can be especially helpful when carpenter bees are a problem. They are trained and equipped to handle carpenter bee infestations in even the most difficult to treat areas.


Center Publication Number: 23

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