Powder Post Beetles and Old House Borers

704-636-0674

There are number of insect species belonging to three separate families which all share the common name "powder post beetles." Adults of these families lay eggs in or on seasoned wood, including untreated wood surfaces in the home (furniture, wood floors and structural timbers), firewood and lumber stock piles. The larvae tunnel through and feed on the wood, converting it to a fine powder. When mature, the adults emerge to mate, leaving the wood surface perforated with small, round "shotholes." Powder post beetles may degrade the quality of lumber, destroy furniture and wooden tools and, in rare cases, they may completely destroy the structural integrity of buildings.


Adult powder post beetle	Powder post beetle larvae	Powder post beetle damage to wood

Description:

Lyctus beetle adults are 3-5 mm (1/8-1/5 inch) long, reddish-brown to black, and somewhat flattened, with the head distinctly visible from above.

Anobiid beetle (furniture beetle and death-watch beetle) adults are 2-5 mm (1/10-1/5 inch) long, reddish-brown to dark brown and covered with fine yellow hairs. Anobiids are cylindrically-shaped--the head is hidden by the thorax when viewed from above.

Bostrichid beetle adults are 3-6 mm (1/8-1/4 inch) long, dark brown to black, cylindrical in shape, and have an enlarged thorax which gives the beetle a humpbacked appearance.

The larvae of these beetles are seldom seen because they live entirely inside wood. Mature larvae are 5 mm (3/16 inch) long and are white with brownish heads and dark mandibles when mature.

Life Cycle:

Lyctus beetles commonly produce one generation per year. Females lay their eggs in the natural pores of timber, infesting only the sapwood of seasoned hardwoods. Eggs hatch in several days and the larvae tunnel into the wood. After pupation, the adults emerge (usually in June), leaving round shotholes on the wood surface. After mating, females will often reinfest the same timber.

Anobiid females lay their eggs on the surface cracks and crevices of wood or in the mouth of old exit holes. Anobiids usually attack the sapwood of seasoned softwoods. Eggs hatch in about a week and the larvae tunnel into the wood. Larvae may live for one to four years. After pupation, the adults emerge, mate and usually reinfest the same timber.

Bostrichid females bore tunnels into the wood to lay their eggs. Eggs hatch in approximately 21 days and the larvae mine the wood for nine months. In another 30 days the mature beetles emerge, mate and usually reinfest the same wood. Bostrichids prefer the sapwood of seasoned hardwoods, though they do attack softwoods.

Control:

• Powder post beetle infestations are most often initiated by introducing infested material into the home. Avoid storing firewood in the home for more than two to three days prior to its use.

• Any building materials introduced into the home should be checked for signs of beetles, damage or larvae.

• A coating of shellac, varnish, wax or paint may prevent an infestation, as Lyctus beetles and Anobiids are unable to oviposit if the pores in the wood are filled. Filling in already existing shotholes can help prevent a reinfestation, if holes are continually filled as new adults emerge.

• Powder post beetles cannot survive in dry wood. Often the long-term solution to a powder post beetle problem is to reduce the moisture level of the wood by reducing humidity. This may involve installing a concrete floor in an old basement and/or installing a dehumidifier.

• Insecticides may be necessary for all but very light infestations in structural timbers. Insecticide solutions are generally painted or sprayed on the wood surfaces. Professional extermination is often necessary. Boric acid treatments have been shown to be effective in control of powder post beetles.

Old House Borers

Size

3/4 to 1 inch (18-25mm)

Color

Black to dark brown

Description

Dark-colored, large, elongated beetle which burrows in structural wood.

Habitat

The chewing sounds produced by the feeding of old house borer larvae can be heard in wood during the spring and summer months.

Life Cycle

The larvae feed little during the winter months of December through February. The larvae can live in seasoned softwood for several years. When the larvae are full grown, which usually takes about five years, they emerge through oval holes in the surface of the wood. Emergence occurs during June and July. During the first few years of feeding, the larvae cannot be heard, but when they are about four years old the chewing sounds are audible.

Type of Damage

Damage occurs to the wood in houses. The actual structural damage caused by these beetles depends on the number of larvae feeding, the extent of the infestation (how many years), and whether there has been a reinfestation.

Control

Control of old house borers involves the use of insecticides applied to the surface of wood or the use of an insecticidal gas or fog. When there is an extensive and active infestation of this insect, fumigation or fogging may be the best control method. However, limited infestations can be controlled by applying insecticides to the surface of the wood to prevent reinfestation and, perhaps, kill larvae that may feed close to the surface and contact the chemical just below the surface.

Interesting Facts

Are not limited to the wood in old houses-attack new houses as well.