Wood Boring Beetles
The wood-boring beetles of economic concern include powderpost beetles, false powderpost beetles, furniture and deathwatch beetles, and the old house borer. Most of the procedures that will prevent their attacks on wood are the responsibility of those who harvest, mill and/or store the wood. Those who use wood must take precautions to reduce the chance of building an infestation into structures and furniture.
The wood-boring beetles of economic concern include powderpost beetles, false powderpost beetles, furniture and deathwatch beetles, and the old house borer. Most of the procedures that will prevent their attacks on wood are the responsibility of those who harvest, mill and/or store the wood. Those who use wood must take precautions to reduce the chance of building an infestation into structures and furniture.
Prevention
Using kiln- or air-dried wood in construction is one of the least expensive and most practical preventive measures. A few beetle species can survive and re-infest wood that has been properly dried. Sealing wood surfaces with varnish, shellac or paint eliminates the habitat necessary for egg laying, but it is usually not feasible to seal the surfaces of structural timbers. Using chemically treated wood (treated by fumigation, wood preservatives or insecticides) will provide that wood remains beetle-free, but using treated wood is usually cost-prohibitive. In addition, fumigation will not protect the wood from future infestation.
Using kiln- or air-dried wood in construction is one of the least expensive and most practical preventive measures. A few beetle species can survive and re-infest wood that has been properly dried. Sealing wood surfaces with varnish, shellac or paint eliminates the habitat necessary for egg laying, but it is usually not feasible to seal the surfaces of structural timbers. Using chemically treated wood (treated by fumigation, wood preservatives or insecticides) will provide that wood remains beetle-free, but using treated wood is usually cost-prohibitive. In addition, fumigation will not protect the wood from future infestation.
Using good building design and practices, including proper ventilation, drainage and clearance between the wood and soil will tend to reduce the moisture content of wood in a structure, creating less favorable conditions for beetle development. Central heating and cooling systems also speed up the wood’s drying process.
There are numerous species of wood-boring insects that show up in houses. If not controlled quickly, some of these can cause considerable damage. Other pests are of minor importance and attack only unseasoned wood. Beetles and wasps all have larval or grub stages in their life cycles, and the mature flying insects produce entry and exit holes in the surface of the wood. These holes, and sawdust from the tunnels they create behind the holes, are generally the first evidence of an attack that’s visible to the building inspector.
Correct identification of the insect responsible for damage is essential if the appropriate control method is to be selected. The characteristics of each of the more common groups of beetles and wasps are discussed in the following table which summarizes the size and shape of entry and exit holes produced by wood-boring insects, the types of wood they attack, the appearance of frass (sawdust) in insect tunnels, and the insect’s ability to re-infest wood in a house.
To use the table, match the size and shape of the exit/entry holes in the wood to those described in the table; note whether the damaged wood is a hardwood or softwood, and whether the damage is in a new or old wood product (evidence of inactive infestations of insects that attack only new wood will often be found in old wood; there is no need for control of these). Next, probe the wood to determine the appearance of the frass. It should then be possible to identify the insect type. It is clear from the table that there is often considerable variation within particular insect groups. Where the inspector is unsure of the identity of the insect causing damage, a qualified entomologist should be consulted.
There are numerous species of wood-boring insects that show up in houses. If not controlled quickly, some of these can cause considerable damage. Other pests are of minor importance and attack only unseasoned wood. Beetles and wasps all have larval or grub stages in their life cycles, and the mature flying insects produce entry and exit holes in the surface of the wood. These holes, and sawdust from the tunnels they create behind the holes, are generally the first evidence of an attack that’s visible to the building inspector.
Correct identification of the insect responsible for damage is essential if the appropriate control method is to be selected. The characteristics of each of the more common groups of beetles and wasps are discussed in the following table which summarizes the size and shape of entry and exit holes produced by wood-boring insects, the types of wood they attack, the appearance of frass (sawdust) in insect tunnels, and the insect’s ability to re-infest wood in a house.
To use the table, match the size and shape of the exit/entry holes in the wood to those described in the table; note whether the damaged wood is a hardwood or softwood, and whether the damage is in a new or old wood product (evidence of inactive infestations of insects that attack only new wood will often be found in old wood; there is no need for control of these). Next, probe the wood to determine the appearance of the frass. It should then be possible to identify the insect type. It is clear from the table that there is often considerable variation within particular insect groups. Where the inspector is unsure of the identity of the insect causing damage, a qualified entomologist should be consulted.
PowderPost Beetles
“Powderpost beetle” is a term used to describe several species of wood-boring insects. Powderpost beetles damage wood slowly; thus, homeowners should not feel as though they must act immediately in order to preserve the structural integrity of their home. A “wait and see” approach is often desirable, especially when there is doubt as to whether the infestation is currently active.
Most powderpost beetles are introduced into homes in lumber or finished wood products, such as furniture and flooring. Lumber that has been improperly dried or stored should not be used, particularly if beetle exit holes are present. Many of the most serious infestations arise from old lumber from a barn or old woodpile that is repurposed to panel a room or build an addition.
Powderpost beetles will only lay their eggs on bare, unfinished wood. Wood that is painted, varnished, waxed or similarly sealed is generally safe from attack, provided no unfinished surfaces are exposed. Bare wood can be protected from attack by painting or finishing exposed surfaces. Beetles emerging from finished articles, such as furniture, were probably in the wood before the finish was applied. However, note that beetles emerging from finished wood can re-infest the wood by laying eggs in their own exit holes. Sealing the holes prevents this possibility.
Powderpost beetles can be found in dead as well as dried and cured lumber. Damage can occur to many wooden components in a home, such as the rafters, joists, flooring, moldings and paneling, as well as crating, furniture, antiques, tool handles, gunstocks, fishing poles and baskets. Homeowners are much more likely to see the damage caused by these beetles than the beetles themselves. Sometimes, homeowners may hear rasping or ticking in the wood at night, notice a blistering appearance on the wood, see powdery frass piles below holes in the wood, or find numerous round or oval exit holes at the wood’s surface. They may even see powderpost beetles collect around windows or lights.
“Powderpost beetle” is a term used to describe several species of wood-boring insects. Powderpost beetles damage wood slowly; thus, homeowners should not feel as though they must act immediately in order to preserve the structural integrity of their home. A “wait and see” approach is often desirable, especially when there is doubt as to whether the infestation is currently active.
Most powderpost beetles are introduced into homes in lumber or finished wood products, such as furniture and flooring. Lumber that has been improperly dried or stored should not be used, particularly if beetle exit holes are present. Many of the most serious infestations arise from old lumber from a barn or old woodpile that is repurposed to panel a room or build an addition.
Powderpost beetles will only lay their eggs on bare, unfinished wood. Wood that is painted, varnished, waxed or similarly sealed is generally safe from attack, provided no unfinished surfaces are exposed. Bare wood can be protected from attack by painting or finishing exposed surfaces. Beetles emerging from finished articles, such as furniture, were probably in the wood before the finish was applied. However, note that beetles emerging from finished wood can re-infest the wood by laying eggs in their own exit holes. Sealing the holes prevents this possibility.
Powderpost beetles can be found in dead as well as dried and cured lumber. Damage can occur to many wooden components in a home, such as the rafters, joists, flooring, moldings and paneling, as well as crating, furniture, antiques, tool handles, gunstocks, fishing poles and baskets. Homeowners are much more likely to see the damage caused by these beetles than the beetles themselves. Sometimes, homeowners may hear rasping or ticking in the wood at night, notice a blistering appearance on the wood, see powdery frass piles below holes in the wood, or find numerous round or oval exit holes at the wood’s surface. They may even see powderpost beetles collect around windows or lights.
Mistakes are sometimes made determining if the infestation is active or non-active. Infestations sometimes die out of their own accord. Therefore, it is important to be able to determine whether the infestation is active or inactive. Active infestation will usually be evidenced by powder the color of fresh-cut wood sifting from the exit holes. In contrast to old, abandoned holes, new holes will not have taken on the weathered appearance of the surrounding wood. Powder or frass streaming from recently opened holes may accumulate in small piles beneath the exit holes. If these piles of powder are covered with a film of dust or debris, the damage is old. Careful observation may be required to distinguish new powder from frass that has been dislodged from old larval galleries by vibration.
One means of confirming that an infestation is active is to mark or seal any existing exit holes. The homeowner can use a crayon or tape over the holes to see if more holes appear. Then the powder should be swept up, and the wood should be re-checked for new holes and powder at a later date. Since most emergence occurs from April to July, it might be worthwhile to wait until the following spring to determine if new holes and fresh powder are present. This is especially useful when attempting to make a determination during the fall or winter months.
Moisture
Powderpost beetles, especially anobiids, have specific moisture requirements for survival. Since wood moisture levels below 13% during spring and summer)are generally unsuitable for anobiid development or re-infestation, it’s advisable to install a moisture barrier in the crawlspace of infested buildings. Covering the soil with 4- to 6-mil polyethylene reduces movement of moisture into the substructure and reduces the threat of an infestation spreading upward into walls and the upper portions (wooden components) of the building.
Most beetles do not develop in wood with a moisture content below 10 to 15%. Another way to lower moisture content in damp crawlspaces is to increase ventilation. This can be accomplished by installing foundation vents at 1 square foot of vent area per 150 square feet of crawlspace. Moisture meters used by some pest-control operators are useful tools for predicting the potential re-infestation in wood.
Lyctid Powderpost Beetles
Lyctids attack only the sapwood of hardwoods with large pores, such as oak, hickory, ash, walnut, pecan, and many tropical hardwoods. They re-infest seasoned wood until it disintegrates. They attack seasoned hardwood and sapwood timbers found in woodwork molding, window and door frames, plywood, flooring, structural wood, furniture, tool handles and firewood. A few species attack softwoods, but pine and soft woods are not normally attacked. Lyctids rarely attack and re-infest seasoned wood or wood that is older than five years. Infestations usually result from wood that contained eggs or larvae when placed in the home. The wood could have been improperly dried or stored. Larvae cause the damage.
Lyctids range from 1/32- to 1/16-inch in length. They are flattened, slender, and reddish-brown to black. The basal abdominal segment is long, and the antennae bear a cub of only two segments. The head is visible from above. Mature larvae are C-shaped, slightly hairy, with three pairs of spine-like legs, and yellowish-white with a brown head.
The presence of small piles of fine flour-like or talc-like wood powder (frass) on or under the wood is the most obvious sign of infestation. The frass could be loosely packed in tunnels. Even a slight jarring of the wood makes the frass sift from the holes. Large quantities of frass often fall out at exit holes and cracks. There are no fecal pellets. The exit holes are round and vary from 1/32- to 1/16-inch in diameter. Most of the tunnels are about 1/16-inch in diameter and loosely packed with fine frass. If damage is severe, within a few years the sapwood may be completely converted to frass that is held in by a very thin veneer of surface wood with beetle exit holes. The amount of damage depends on the level of starch in the wood. The length of the life cycle for lyctids is three months to one year.
One means of confirming that an infestation is active is to mark or seal any existing exit holes. The homeowner can use a crayon or tape over the holes to see if more holes appear. Then the powder should be swept up, and the wood should be re-checked for new holes and powder at a later date. Since most emergence occurs from April to July, it might be worthwhile to wait until the following spring to determine if new holes and fresh powder are present. This is especially useful when attempting to make a determination during the fall or winter months.
Moisture
Powderpost beetles, especially anobiids, have specific moisture requirements for survival. Since wood moisture levels below 13% during spring and summer)are generally unsuitable for anobiid development or re-infestation, it’s advisable to install a moisture barrier in the crawlspace of infested buildings. Covering the soil with 4- to 6-mil polyethylene reduces movement of moisture into the substructure and reduces the threat of an infestation spreading upward into walls and the upper portions (wooden components) of the building.
Most beetles do not develop in wood with a moisture content below 10 to 15%. Another way to lower moisture content in damp crawlspaces is to increase ventilation. This can be accomplished by installing foundation vents at 1 square foot of vent area per 150 square feet of crawlspace. Moisture meters used by some pest-control operators are useful tools for predicting the potential re-infestation in wood.
Lyctid Powderpost Beetles
Lyctids attack only the sapwood of hardwoods with large pores, such as oak, hickory, ash, walnut, pecan, and many tropical hardwoods. They re-infest seasoned wood until it disintegrates. They attack seasoned hardwood and sapwood timbers found in woodwork molding, window and door frames, plywood, flooring, structural wood, furniture, tool handles and firewood. A few species attack softwoods, but pine and soft woods are not normally attacked. Lyctids rarely attack and re-infest seasoned wood or wood that is older than five years. Infestations usually result from wood that contained eggs or larvae when placed in the home. The wood could have been improperly dried or stored. Larvae cause the damage.
Lyctids range from 1/32- to 1/16-inch in length. They are flattened, slender, and reddish-brown to black. The basal abdominal segment is long, and the antennae bear a cub of only two segments. The head is visible from above. Mature larvae are C-shaped, slightly hairy, with three pairs of spine-like legs, and yellowish-white with a brown head.
The presence of small piles of fine flour-like or talc-like wood powder (frass) on or under the wood is the most obvious sign of infestation. The frass could be loosely packed in tunnels. Even a slight jarring of the wood makes the frass sift from the holes. Large quantities of frass often fall out at exit holes and cracks. There are no fecal pellets. The exit holes are round and vary from 1/32- to 1/16-inch in diameter. Most of the tunnels are about 1/16-inch in diameter and loosely packed with fine frass. If damage is severe, within a few years the sapwood may be completely converted to frass that is held in by a very thin veneer of surface wood with beetle exit holes. The amount of damage depends on the level of starch in the wood. The length of the life cycle for lyctids is three months to one year.
Anobiid Beetles
The most common anobiids attack the sapwood of hardwoods and softwoods. They re-infest seasoned wood if environmental conditions are favorable. Attacks often start in poorly heated or ventilated crawlspaces and spread to other parts of the house. They rarely occur in houses on slab foundations. Anobiids prefer to infest wood that is damp; therefore, infestation usually begins in moist, poorly ventilated areas, such as crawlspaces, basements, garages and utility sheds. Under favorable conditions of moisture and temperature, infestations may occur as the result of using infested lumber, from beetles flying in from outdoors, or from beetles living in firewood that is carried indoors.
Infestations develop slowly, but wood can be re-infested year after year.
Anobiids are called “deathwatch beetles” because, in the past, superstitious people believed that the ticking sound that one species makes foretold an impending death in the household. Adult beetles make the sound during the mating season by tapping their heads on a hard surface.
Adult anobiids have slender, cylindrical bodies that range from 1/16- to 1/4-inch in length, and are reddish-brown to nearly black. The head is bent downward. The widest point of the thorax is slightly forward of the base, tapering backward and appearing as a rough, diamond-shaped outline. Larvae are C-shaped and nearly white except for a dark head. The length of the life cycle for anobiids is one year to three years. Adult insects are rarely seen. Anobiids typically leave a small amount of frass around their exit holes. The most obvious sign of infestation is the accumulation of powdery frass and tiny pellets underneath infested wood or streaming from exit holes. The exit holes are round and vary from 1/16- to 1/8-inch in diameter. Lyctid frass is extremely fine and feels like talc when rubbed between the fingers. Anobiid frass is also powder-like but feels gritty.
A way to differentiate holes made by lyctids from those created by anobiids is to insert a click-type or retractable ballpoint pen into the exit hole; only the tip of the ball will fit through a lyctid emergence hole. If the hole was made by an anobiid, the tip of the pen will enter part way up the angled face of the point because anobiid holes are slightly larger than lyctid holes.
The most common anobiids attack the sapwood of hardwoods and softwoods. They re-infest seasoned wood if environmental conditions are favorable. Attacks often start in poorly heated or ventilated crawlspaces and spread to other parts of the house. They rarely occur in houses on slab foundations. Anobiids prefer to infest wood that is damp; therefore, infestation usually begins in moist, poorly ventilated areas, such as crawlspaces, basements, garages and utility sheds. Under favorable conditions of moisture and temperature, infestations may occur as the result of using infested lumber, from beetles flying in from outdoors, or from beetles living in firewood that is carried indoors.
Infestations develop slowly, but wood can be re-infested year after year.
Anobiids are called “deathwatch beetles” because, in the past, superstitious people believed that the ticking sound that one species makes foretold an impending death in the household. Adult beetles make the sound during the mating season by tapping their heads on a hard surface.
Adult anobiids have slender, cylindrical bodies that range from 1/16- to 1/4-inch in length, and are reddish-brown to nearly black. The head is bent downward. The widest point of the thorax is slightly forward of the base, tapering backward and appearing as a rough, diamond-shaped outline. Larvae are C-shaped and nearly white except for a dark head. The length of the life cycle for anobiids is one year to three years. Adult insects are rarely seen. Anobiids typically leave a small amount of frass around their exit holes. The most obvious sign of infestation is the accumulation of powdery frass and tiny pellets underneath infested wood or streaming from exit holes. The exit holes are round and vary from 1/16- to 1/8-inch in diameter. Lyctid frass is extremely fine and feels like talc when rubbed between the fingers. Anobiid frass is also powder-like but feels gritty.
A way to differentiate holes made by lyctids from those created by anobiids is to insert a click-type or retractable ballpoint pen into the exit hole; only the tip of the ball will fit through a lyctid emergence hole. If the hole was made by an anobiid, the tip of the pen will enter part way up the angled face of the point because anobiid holes are slightly larger than lyctid holes.
If there are large numbers of holes and the powder is bright and light-colored, similar in appearance to freshly sawed wood, the infestation is both old and active. If all the frass is yellowed and partially caked on the surface where it lies, the infestation has been controlled or has dried out naturally. Anobiid tunnels are normally loosely packed with frass and pellets. It may take 10 years or more before the number of beetles infesting wood becomes large enough for their presence to be noted. Control can be achieved by both chemical and non-chemical methods. For current information on the control of anobiids, the inspector should contact the entomologist at his nearest land-grant university or a reputable pest control company.
Bostrichid Powderpost Beetles
Bostrichids are more abundant in the tropics. Bostrichids range from 1/32- to 3/8-inch in length, and their coloring is reddish-brown to black. Most species have a cylindrical shape. Their thorax is roughened. The antennae bear a club of three distinct segments. The head is usually not visible when viewed from above. Larvae are C-shaped; the body segments immediately behind the head capsule are much wider than the body segments at the rear.
The first signs of infestation are circular entry holes made by the females for their egg tunnels. The exit holes made by other adults are similar but are usually filled with frass. The frass is fine to coarse and contains no pellets. It is tightly packed in the tunnels and does not sift out of the wood easily. The frass tends to stick together.
The exit holes are round and vary from 3/32- to 9/32-inch in diameter. Bostrichid tunnels are round and range from 1/16- to 3/8-inch in diameter. If damage is extreme, the sapwood may be completely consumed. Bostrichids rarely cause significant damage in framing lumber. They primarily affect individual pieces of hardwood flooring and trim. Replacement of structurally weakened members is usually the most economical and effective control method.
Bostrichid Powderpost Beetles
Bostrichids are more abundant in the tropics. Bostrichids range from 1/32- to 3/8-inch in length, and their coloring is reddish-brown to black. Most species have a cylindrical shape. Their thorax is roughened. The antennae bear a club of three distinct segments. The head is usually not visible when viewed from above. Larvae are C-shaped; the body segments immediately behind the head capsule are much wider than the body segments at the rear.
The first signs of infestation are circular entry holes made by the females for their egg tunnels. The exit holes made by other adults are similar but are usually filled with frass. The frass is fine to coarse and contains no pellets. It is tightly packed in the tunnels and does not sift out of the wood easily. The frass tends to stick together.
The exit holes are round and vary from 3/32- to 9/32-inch in diameter. Bostrichid tunnels are round and range from 1/16- to 3/8-inch in diameter. If damage is extreme, the sapwood may be completely consumed. Bostrichids rarely cause significant damage in framing lumber. They primarily affect individual pieces of hardwood flooring and trim. Replacement of structurally weakened members is usually the most economical and effective control method.