Wood-boring Beetle – Detail

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Powderpost beetles

The adults are very small, less than 1/4″ in size. They are flattened and reddish-brown to black in color. Larvae are white, cream colored, shaped with dark brown heads. Larvae create tunnels in the wood and become pupae. As adults they bore out through the wood, pushing a fine powdery dust out. The shape of their holes are round ,about 1/32-1/16 pinholes.

The term “powderpost” comes from the fact that the larvae of these beetles feed on wood and, given enough time, can reduce it to a mass of fine powder. They are therefore considered pests. The family Anobiidae is the only one capable of digesting cellulose, the primary ingredient of wood, and all other species excrete the wood without digesting it.

Powderpost beetles spend months or years inside the wood in the larval stage. Their presence is only apparent when they emerge from the wood as adults, leaving pin hole openings, often called “shot holes” behind and piles of powdery frass below. Shot holes normally range in diameter from 1/32 inch, (0.8 mm) to 1/8 inch (3 mm), depending on the species of beetle. If wood conditions are right, female beetles may lay their eggs and reinfest the wood, continuing the cycle for generations. Heavily-infested wood becomes riddled with holes and rooms or basements packed with a dusty frass  wood that has passed through the digestive tract of the beetles. The larvae feed mainly upon starch in the wood.

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Deadthwatch beetles

The death watch beetle (Anobiidae) is a woodboring beetle, namely a beetle whose larvae are xylophagous. The adult is approximately 7 mm long. The larva can be up to 11 mm long.

Deathwatch beetles are closely related to the drugstore and cigarette beetles, which are stored-product pests. Adults communicate with each other and probably locate mates by tapping their heads against wood, usually at night. (Deathwatch beetles supposedly acquired their name during medieval European times from people who heard the tapping while sitting up with a sick or dying person during the night.) Adults are reddish to dark brown and lay eggs in crevices or small openings or pores in unfinished wood. Two years may be required to complete each generation.

Deathwatch beetles are found primarily in soft woods, including girders, beams, foundation timbers, and some types of furniture. Some species attack books. This beetle is typically found in old wood and may be associated with wood that is partially decayed. Deathwatch beetles prefer wood that is more moist (greater than 14% moisture) than what powderpost beetles prefer and may be less of a problem in houses with central heating and air conditioning. Larvae of deathwatch beetles fill their galleries with small pellets of frass (smaller than the pellets produced by drywood termites), which distinguish them from other wood borers. None of the other boring beetles produce pelletized frass.

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False powderpost beetles

The Bostrichidae are a family of beetles with more than 700 described species. They are commonly called auger beetles, false powderpost beetles or horned powderpost beetles. The head of most auger beetles cannot be seen from above, as it is downwardly directed and hidden by the thorax.

Adults are dark brown or black, sometimes with reddish mouthparts, legs, and antennae. Adults of most species are about 1/4 inch long, but in some species, adults reach 1-1/2 to 2 inches in length. Adult beetles have a humpback appearance, so their head is not visible when viewed from above. This characteristic is also seen in deathwatch beetles.

Females bore a tunnel, or egg gallery, into wood or other materials, then deposit their eggs in pores or cracks within the tunnel. Adults of some species bore through soft metal, such as lead and silver, as well as plaster and other nonwood materials, searching for sites to deposit eggs or for protection from weather extremes. This gives rise to the common name “leadcable borer” given to one species because of its habit of boring into the metal covering of suspended telephone wires. In buildings, false powderpost beetles infest floors, furniture, hardwood paneling, and other wood materials.

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Oriental wood borer (Waterhouse)

Oriental wood borer (Heterobostrychus aequalis). This genus is about 6-13mm long in length and is reddish-brown to brownish-black in color. The head is not visible from above, as it is recessed beneath the pronotum. The anterior half of the pronotum has broad, toothlike marginal tubercles. The elytra have several rows of deep pits, and toward the rear the wing covers curive inward creating a concave area that in the males is equipped with two stout spines.

The larva is white to yellowish, with a characteristic bostrichid shape, variable in size with most last instars averaging 10 mm. The mandibles are black, conical and the darkest area on the larva. All stages are found in dry lumber which is eaten by the adults and larvae. The eggs are deposited on rough surfaces of sawed lumber and logs, in holes, cracks or short tunnels made by the female. The larval borings may be 1/4 inch wide, winding for several inches. The tunnels are usually filled with tightly packed, fine, sawdust-like material which is characteristic of this genus. Tunnels of most pinhole and shothole borers contain very little such material. Pupation occurs in a cell at the end of the tunnel.

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Oriental wood borer (Waterhouse)

The adult emerges through an exit hole, often after chewing through a few inches of wood. Length of development from egg to adult is variable from one to several years (up to six years recorded). Apparently they can survive under dry conditions present in manufactured wood products and emerge several years later, as do some of the Cerambycidae.

Its habit of boring in packing cases, boxes, plywood, furniture and lumber make it a serious pest. In heavy infestations the wood is often reduced to powder to a depth of 2 to 3 inches. It is a threat to nearly all wood products, and has even been recorded as boring into the lead linings of boxes. In hardwoods, the damage is usually confined to the sapwood, but may extend deeper in soft woods.

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Sanitation Practices

Wood-boring beetles are difficult to control once an infestation has begun. Prevention is the best management method. Protective measures should be taken at every stage of lumber processing and handling including lumber mills, plywood mills, lumber yards, furniture manufacturing factories, and building construction firms.

Sanitation is the most important aspect of prevention. Remove and destroy dead tree limbs around buildings or near any area where wood products are stored. Destroy scrap lumber and other wood products before they become infested. Kiln drying of lumber destroys beetle infestations, although it does not prevent reinfestation.

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Protection

Materials used for construction of buildings and wood furniture should be thoroughly inspected before use to be certain that they do not contain wood-boring beetles. Apply liquid insecticides as primary materials for application to structural wood for preventing and remediating infestations of wood-boring beetles.

Protect wood from infestation by painting or varnishing to seal pores, cracks, and holes where eggs could be laid. Most beetle problems are introduced into homes in lumber or finished wood products (i.e., furniture, paneling, or flooring). Most serious infestations occur when infested wood is installed in the house. Inspect wood to insure that wood is not infested at the time of home construction.

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Wood finishes

Powderpost beetles only lay eggs on bare, unfinished wood. Beetles will not infest wood that is painted, varnished, waxed, or similarly sealed. Beetles emerging from painted or varnished wood were either in the wood before finishing or were a result of reinfestation by eggs that were laid in emergence holes of adult beetles. Sealing holes prevents reinfestation from eggs laid within the hole.

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Wood replacement

Infested wood can be replaced if the infestation appears to be localized. For instance, if emergence holes appear in a member of a door or window frame, the piece can be removed and replaced with a new, uninfested wood.