Each year, many households in Maryland become infested by a
variety of wood destroying insects, the most notable being termites. If left
unchecked they can cause serious structural damage to a home. In fact, in the
United States, termites do more damage to homes annually than all reported
fires, tornadoes, hurricanes and windstorms combined.
The termite species that is indigenous to Maryland is the
Eastern Subterranean Termite (Reticulitermes flavipes). As its name implies,
it lives beneath the soil. Termites, like ants and bees, are social insects and
live in colonies. The termite colony is comprised of several castes including
a queen, soldiers, winged reproductives (swarmers) and workers. The winged
reproductives, or swarmers, are the form most commonly seen by homeowners. Ant
colonies also release winged reproductives (flying ants). Many times termite
infestations go unchecked when a homeowner mistakes termite swarmers for flying
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While termite swarmers are a nuisance, they do not cause
damage. Their sole function is to find a mate and begin a new colony. The
"worker" caste makes up the bulk of the termite colony and is the only
individual in the colony that forages for food and is directly responsible for
causing damage to wood and cellulose containing materials. They have no eyes or
wings and are soft-bodied, whitish in color and approximately 1/4 inch in
The soldiers also have no eyes or wings. They do, however, have
enlarged jaws called mandibles which they use to defend the termite colony.
They are otherwise similar in appearance to the workers of the colony, whitish
in color but their head is enlarged and sometimes brown in color.
Termites are different from almost all other insects in that
they can convert the cellulose in wood products back into sugar and utilize it
as a food source. In nature, termites are beneficial as they help convert dead
wood and other materials containing cellulose into humus. Some other types of
insects, such as powderpost beetles and old house borers, eat wood but cannot
convert the cellulose to sugar. They receive nourishment from the sugars and
starch which the tree stored during its growth. Still other insects, such as
carpenter ants and carpenter bees, get no food whatever from the wood but
simply excavate holes and cavities in the wood to provide protective shelter.
There are a number of ant species that infest homes and
buildings. However, the carpenter ant is perhaps the only species that damage
wood and are encountered in homes. They do not consume the wood but only build
their nests within it. Their foods, similar to those of many other
house-infesting ants, are found in kitchens, pantries and other areas where
food is stored. Carpenter ants are the largest of the house-infesting ants.
Workers within the colony range in size from about 3/16 to 5/8 inches in
length. Color varies among species, although black seems to be predominant.
Carpenter ants, like termites, tend to prefer wood that is
partially decayed by wood rot. However, they will also attack perfectly sound
wood as well. They excavate wood members of buildings, especially when a cavity
or enclosed space already exists. Often, these cavities are enlarged to the
point that structural damage occurs, but more often the movement of foraging
ants within a structure becomes a nuisance. Carpenter ants may travel or forage
for distances of several hundred feet. They keep the inside of their
excavations clean by discarding the litter of large wood particles (frass) out
of the most convenient opening. The coarse frass, when discarded, can be an aid
in locating the colony for control purposes.
Wood Boring Beetles
In addition to termites and carpenter ants, there are a number
of other wood destroying insects that can attack wood members in structures.
The two most notable are the old house borer beetle and the powder post beetle.
Both of these beetles are found in Maryland. The Lyctid powder post beetle
attacks only the sapwood of hardwoods with large pores, e.g., oak, hickory,
ash, walnut, or pecan, and feeds on starch in the wood. Lyctids range from 1/8
to 1/4 inch in length and are reddish-brown to black in color. The presence of
small piles of fine powder (frass) under the wood is the most obvious sign of
infestation. The exit holes are round and vary from 1/32 to 1/16 inch in
diameter. The larvae are tiny "C" shaped grub-like larvae that are found
feeding in tunnels in the wood. Powder post beetles can reinfest the same piece
of wood until it is reduced to a shell of frass with the consistency of face
powder held in by a very thin veneer of surface wood with beetle exit holes.
The old house borers are members of a large
beetle family called the long-horned beetles, named because of their long
anntenae. The old house borers were imported from Europe in infested lumber.
Unlike the powder post beetle, they attack only the sapwood of softwoods such
as pine, spruce, fir and hemlock. The adults emerge in early summer, living for
approximately 16 days, during which time the females lay approximately 150 to
200 eggs in cracks or crevices in the wood. The larvae that hatch bore into the
wood and take up to ten years to complete their life cycle. The larvae cause
the damage by feeding on the wood. The rasping and ticking of their feeding
activity is often the first sign or indication of infestation that a homeowner
may detect. When the adults emerge they create oval shaped holes in the surface
of the wood that are approximately 1/4 inch in diameter. The galleries in the
wood are filled with fine frass mixed with small pellets.
Carpenter bees are other wood destroying insects that can be
found in Maryland. They are large bees that look very much like bumble bees.
The major difference is that carpenter bees have a bare, shiny black abdomen
whereas bumble bees have a hairy abdomen with some yellow markings. Male
carpenter bees are agressive but harmless as they have no stinger. However,
females can and will sting if they feel threatened.
Carpenter bees cause damage to wood when they bore holes to
create a tunnel in which to raise their young. They prefer softwood such as
pine, poplar, cedar and redwood for nesting. The holes they bore are quite
distinctive in that they are approximately 1/2 inch in diameter and almost
Other Wood-Inhabiting Insects
There are several other species of insects that damage wood.
However, these insects only infest dying or freshly cut trees or unseasoned
wood. They do not infest wood that has been kiln dried or seasoned . The
ambrosia beetles, bark beetles, horntails (wood wasps), and flat-headed borers
fall into this group of wood-inhabiting insects. Control measures are not
needed to prevent further damage since the wood was infested prior to milling.
Evidence of infestations, such as holes or tunnels, resulting from these
insects can be seen on the surface of milled lumber.
Ambrosia Beetles - These insects attack unseasoned softwood
and hardwood logs. They produce small, 1/50 to 1/8 inch, circular holes. The
bore holes do not contain frass, but are frequently stained blue, black or
Bark Beetles - These insects tunnel at the point where the
wood and bark meet and etch the surface of the wood contacting the bark.
Beetles left under bark edges on lumber may survive for a year or more as the
wood dries. They do not infest wood.
Horntails - These insects generally attack unseasoned
softwoods and do not reinfest seasoned wood. They attack both sapwood and
heartwood, producing a tunnel which is roughly C-shaped in the tree. Tunnels
are tightly packed with coarse frass and are 1/6 to 1/4 inch in diameter.
Frequently, tunnels of emerged insects are exposed on the surface of milled
Consumer Information Regarding Wood Destroying Insects
This consumer information sheet answers commonly asked
questions about inspecting for and controlling wood destroying insects.
1. I think I may have termites (or other wood
Destroying insects) in my home. How can I be sure?
Call a licensed pest control firm to inspect, and always get a second or third
opinion. If you can collect a specimen of the insect you may wish to take it to
the Maryland Cooperative Extension Service Home and Garden Information Center
2. What is the proper way to treat a home for
The basic principle in treating for subterranean termites is to
establish a continuous chemical barrier in the soil immediately adjacent to the
foundation walls, both on the interior and exterior of the structure. This is
normally accomplished by injecting the chemical (termiticide) beneath the soil.
The treatment methods will vary depending on the construction of the structure.
The methods used are slightly different for homes with basements as opposed to
those with crawl spaces or those with slab on ground construction. The amount
of termiticide used will also depend on the size of the structure to be
treated. Before contracting with a firm, ask for a written proposal that
details the method of application and the approximate amount of termiticide to
3. Once my home is treated, am I guaranteed
Against reinfestation of termites?
Even if your home is treated, no one can guarantee that you will never have a
termite problem again. Termites only need a small gap in the chemical barrier
to continue to gain access to your home. If the soil around the home is
disturbed, it can affect the chemical barrier and allow access for termites.
For this reason, most pest control firms give a one year renewable arranty on
termite work. Typically, the warranty states that if a reinfestation occurs
during the lifetime of the warranty they will retreat at no cost to the
consumer. Additionally, some firms also offer repair warranties that give
coverage for termite damage that occurs subsequent to their treatment. Be sure
you read and understand any warranty that is offered.
4. What Is The Proper Way to Treat a Home For
Unlike termites, carpenter ant colonies are not located beneath the soil.
Therefore, a termite treatment will not aid in controlling carpenter ants.
Carpenter ant control can be very difficult. The key factor in bringing them
under control is to find the nest. The most complete control is accomplished
when the nest is located and treated. Infestations can be reduced by treating
travel routes that the workers use while foraging. Outdoor barrier treatments
can help reduce infestation that originate outdoors.
5. One firm recommends fumigation while the other
Recommends topical application, who is right?
Fumigation and topical application of a liquid insecticide are two approved
methods used in controlling infestations of wood boring beetles. Both have
their advantages and disadvantages. One advantage to the fumigation process is
that the fumigant will kill all life stages of the beetles (eggs, larvae,
pupae, adults). A disadvantage in the eyes of some is that the fumigation
process can be expensive. The topical application of liquid insecticide is
generally less expensive. However, it does not control all of the life stages
of the beetles. The pesticide is applied to the wood surface and penetrates a
short distance into the wood. The insects are killed when they come into
contact with the treated area of the wood.
6. What termiticide works best?
There are currently a number of termiticide (termite pesticides) products on
the market. All have been proven to be effective in controlling termites when
applied properly in accordance with label directions. One product does not
necessarily do a better job than another in controlling termites.
For further information regarding either
inspection for or control of wood destroying insects you can contact the
Pesticide Regulation Section of the Maryland Department of Agriculture at
410-841-5710. Another excellent source of information is the Maryland
Cooperative Extension Service Home and Garden Information Center. Contact them at: extension.umd.edu/hgic
Send E-mail to Robert Hofstetter