Q: Our biggest problem relates to carpenter bees. They dive into the wood, dig holes and destroy whole sections of siding. What can I do?
A: Often mistaken for black bumblebees, the shinier, less hairy carpenter bees are not much of a threat to humans. The males, with an aggressive flight pattern and loud buzz, cannot sting. The less aggressive females can bite if cornered. Overall, these are beneficial insects, but they can become a significant problem in some weathered or unpainted woods when female carpenter bees build or enlarge their nests.
This damage can be exacerbated by woodpeckers, which often attack the nests while foraging for food. These insects have distinct preferences for certain species of softwoods, including yellow pine, white pine, California redwood, cedar, Douglas fir and cypress. The areas of residential structures most commonly attacked are roof trim and siding, exterior columns, steps, decks, and porch beams and railings. Entrance holes to the bees' tunnels are very round and regular. Typically the bees tunnel into the wood about an inch, then abruptly redirect the tunnel at a right angle traveling with the grain of the wood for 4 to 6 inches. However, a system of galleries developed by several bees working in the same area over a period of time can extend as much as 6 to 9 feet within a wood beam or siding panel.
Previously damaged or especially vulnerable areas can be covered or replaced with aluminum, asphalt or fiberglass materials. The holes can be filled with steel wool and then covered with metal window screening. Wood fillers and caulks are often too soft to prevent reentry by the bees.
New infestations can be avoided by keeping the wood painted or heavily varnished. This means repainting as frequently as necessary to keep up with weathering. Pay particular attention to maintaining the paint on the undersides of siding or trim that is accessible to bees but not easily visible to humans. The bees often are attracted to depressions in wood, so be sure to fill these before painting. Unfortunately, clear and semitransparent stains won't deter them.
Many of these avoidance techniques are not feasible with wood siding, so chemical treatments remain the best option. If a pesticide is considered, use one that is pyrethrum-based. This type of insecticide can be used to kill the bees directly, but it does not pose significant hazards to mammals due to a very short residual life of 24 to 48 hours. Revenge, a pyrethrin plus silica aerogel mixture in an aerosol can, is effective and can be sprayed directly on the bees and applied to the entrance of their galleries to deter these insects.
Products sold for wasp control, such as the insecticide Baygon--frequently listed on labels as 2-(l-methylethoxy) phenyl methylcarbamate, or resmethrin--and designed for long-distance application (from 10 to 13 feet) can also be effective. Apply an insecticide directly into the nest entrances. Spray in the evening, when most of the bees are in the nest and less active. To ensure proper use, always read the label directions before applying. Recurring signs of bee activity will require subsequent reapplication of the insecticide.
Q: I read your article recommending professional exterminators for dealing with termites. Are you aware that there is a fairly new product on the market called Sentricon (manufactured by Dow) that kills the entire colony, not just the workers, who invade a house? It does not require any tenting or harsh chemicals. It is a system of monitoring tubes placed in the ground, and when one is found to have been hit by termites, the monitoring device is replaced with bait. The termites carry the bait back to the colony and it is eliminated.
A: The system you refer to is good for monitoring the activity of subterranean termites, which are the most prevalent kind in the nation. However, it is not recommended as the sole method of protection.
Although part of the life cycle of the subterranean termite is spent in the ground, this insect also swarms during the reproductive cycle and can enter your house in flight as well as by tunneling at ground level. The Sentricon system is not effective in determining the presence of dry-wood termites, which do not spend any of their life cycle in the ground. This variety of termite is found along both the Atlantic and Pacific coastal strips in the warmer climes, as well as along the Gulf of Mexico and in a few other areas including Tacoma, Wash.
The cost of inspection by a professional is affordable, compared with that of lost equity from termite damage. Most pest-control firms recommend an annual termite inspection, as termites can move in within hours and remain hidden for years, though subterranean termites will return to the ground area in their life cycle and may very well be detected by the Sentricon system at this stage.
Q: Squirrels have invaded our attic. They are noisy and I am concerned about the damage they may do. How can I get rid of these pests?
A: Squirrels are basically tree dwellers that feed on nuts, fruits, seeds and fungi. However, as we encroach on and change their natural environment, these furry critters are often attracted to our houses to build their nests in chimneys and attics. They can be very destructive, chewing through wood, electrical wiring and insulation.
The trick to eliminating these pests is to change the household environment so that it is no longer appealing or accessible. Leave a light or radio on in the attic or chimney for one week and the squirrels will leave, assuming that the young are old enough to travel. Squirrels usually have two litters a year, with three to four offspring each, in spring and late summer.
Another deterrent is to spray a solution of ammonia and water--mixed in equal parts--along the roof line and eaves, in the attic area being invaded and around the chimney. After-shave lotion is just as repulsive to squirrels and can be used in the same manner to drive them out.
Once the critters have exited, cover attic vents with hardware cloth. Use a fire-rated chimney cap with wire mesh on the sides. Seal off other cracks and holes. Trim tree limbs back away from the roof 7 to 9 feet. These preventive measures will keep these unwanted house guests from returning.
Send e-mail to email@example.com or write to Here's How, Copley News Service, P.O. Box 120190, San Diego, Calif. 92112-0190. Only questions of general interest can be answered in the column.