Columnist comments on “dive-bombing” carpenter bees
Morgan County Extension Agent
Have you been walking around the house lately and been dive bombed by some bumble bee looking bees? These pests are most likely carpenter bees. Carpenter bees appear in the early spring when they are active.
Adult carpenter bees are quite large (about 1 inch or slightly longer). They are blackish in color and have yellow hair 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 have yellowish hairs on top of their abdomen.
Carpenter bees burrow into the exposed dry wood of buildings, telephone poles, fence posts, and other wood causing an unsightly appearance to the wood and structural weakness. They usually choose wood that is soft and easy to work, like 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 six days. Galleries normally run with the grain for four 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.
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.
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 (not immediately) if applied directly to them.
Liquid insecticide sprays of a synthetic pyrethroid, such as permethrin, (Spectracide Carpenter Ant & Termite Killer Insect Spray Concentrate), cyfluthrin (Bayer Advanced Power Force Carpenter Ant & Termite Killer Plus Concentrate) and bifenthrin (Ortho-Klor Termite & Carpenter Ant Killer Concentrate) can be sprayed on wood surfaces to reduce carpenter bee activity. The expected residual effectiveness of these insecticides on exterior surfaces is less than 30 days, so re-application may be necessary for long-term control. An unsightly insecticide deposit could occur on treated wood so care should be taken. Nests or galleries can be treated directly with these insecticides. Carpenter bees will be controlled when they contact the residual insecticide.
Several days following treatment (after carpenter bee activity has ceased) holes can be plugged with dowel rods, plastic wood or with other suitable materials (caulk or cork plugs). If carpenter bees continue to attack the wood, additional residual insecticide treatments may be required at weekly intervals.
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 weathered 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. Spraying pyrethrins can be effective as well. Pyrethrins are chemicals 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.
For additional information on carpenter bees and other homeowner questions, contact your local UGA Cooperative Extension office.
Printed in the April 30, 2009 Edition