Powder-Post Beetles in Buildings: What to Do About Them

Part 1

Produced by Tom Cosmas compiled from images made available by The Internet Archive.

Powder-post Beetles in Buildings

What to Do About Them

by R. A. St. George and T. McIntyre

POWDER-POST BEETLES

in Buildings

what to do about them

Leaflet No. 358

U.S. DEPARTMENT OF AGRICULTURE

Powder-Post Beetles in Buildings

WHAT TO DO ABOUT THEM

Powder-post beetles cause extensive damage to wood in the structure of buildings and to wood products used in homes.

The larvae, or grubs, feed on the starch or the cellulose in wood. As they feed, they bore irregular tunnels through the wood. Borings left in the tunnels have the consistency of powder.

Powder-post beetles can be controlled by applying an insecticide to the infested wood. How it is applied depends on the kind of beetle to be controlled and on the extent and location of the infestation. In some circumstances a spray will suffice; in others, fumigation is necessary.

+--------------------------------------------------------------+ | | | COMMON AND SCIENTIFIC NAMES OF INSECTS DISCUSSED | | | | Southern lyctus beetle Lyctus planicollis | | Common furniture beetle Anobium punctatum | | Death-watch beetle Xestobium rufovillosum | | Old house borer Hylotrupes bajulus | | Red-shouldered shothole borer Xylobiops basilaris | | Black-horned pine borer Callidium antennatum | | Bamboo powder-post beetle Dinoderus minutus | | Bamboo borer Chlorophorus annularis | | | +--------------------------------------------------------------+

KINDS

Powder-post beetles are divided into five groups--lyctus beetles, anobiid beetles, bostrichid beetles, cerambycid beetles, and cossonid weevils.

Lyctus beetles are reddish to blackish, about 1/4 inch long, and slightly flattened. One common species is known as the southern lyctus beetle.

Anobiid beetles are similar to lyctus beetles in color and size, but are cylindrical. The common furniture beetle and the death-watch beetle belong in this group.

Bostrichid beetles are reddish, brown, or black; they are 1/8 to 3/4 inch long, and cylindrical.

The heads of anobiids and bostrichids are directed downward and are covered by a "hood."

The cerambycids, also known as roundheaded or long-horned beetles, are blue, black, or pale yellow to reddish brown, and often bear distinctive markings on the head or the wing covers. They are 1/2 to 1 inch long, and vary in shape. The old house borer belongs in this group. It is black, and has grayish markings on the wing covers. It is about 3/4 inch long.

Cossonid weevils are reddish brown or black, 1/8 to 1/5 inch long, and oval to cylindrical. Their heads are drawn out to form a short, broad beak. Cossonids are the only weevils that infest wood; other weevils infest grain or growing crops.

LIFE CYCLE

The adult females lay eggs on or in wood. The eggs hatch into larvae, which develop as they tunnel the wood. The tunneling continues throughout the larval stage, which lasts for months or years, depending on the kind of beetle.

The full-grown larvae transform to pupae, which become adult beetles.

The adults of many kinds of powder-post beetles bore circular holes to the surface of the wood and emerge; others make oval holes. Some emerge in early spring; others, including the old house borer, emerge in early summer. Mating and egg laying follow.

The life cycle of lyctus beetles varies from 3 months to 1 year, depending on the species and on regional differences in temperature, moisture, and availability of wood of high food value.

Part 2

The life cycle of anobiid beetles is sometimes completed in about 1 year and sometimes in 2 years.

Most of the bostrichids and cerambycids complete the cycle in about 1 year, but a few of the latter require several years. The old house borer, a cerambycid, requires 5 to 7 years in the North, and less time in the South. In all but a few months of its life cycle, it is in the larval stage. Larvae 3 or 4 years old are often found in the woodwork of buildings only 1 or 2 years old--evidence that stored lumber is a source of infestation.

Cossonid weevils complete the cycle in about 1 year.

EGG LAYING

The females lay eggs on or in wood that satisfies their egg-laying requirements and the food requirements of the larvae. These requirements differ among the species. Hence different kinds of wood are infested by different species of beetles.

Lyctus beetles infest hardwoods. Cossonid weevils infest softwoods. Some anobiids, bostrichids, and cerambycids infest hardwoods, and some infest softwoods.

For some species bark is an egg-laying requirement; for others it is not.

Some anobiids infest moist wood containing decay organisms, which appear to aid development of the larvae.

Cover: Adult of an anobiid beetle, Xyletinus peltatus, and pine sill damaged by larvae of this beetle.

The porosity of the wood, the moisture content, the starch or cellulose content--these also relate to egg laying.

The adults of some species remain on the wood from which they emerge, and reinfest it. Others crawl or fly to similar wood and attack it.

A beetle may lay only a few eggs or as many as 60 or 70; the number depends on the species of beetle and on the condition of the wood.

=Infestations in Hardwoods=

Seasoned hardwoods.--Beetles that infest seasoned hardwoods lay eggs on or in the wood from which they emerge. Hence the same wood may be infested repeatedly. These beetles do not require bark for egg laying.

Lyctus beetles lay eggs in exposed pores in the sapwood of oak, ash, hickory, walnut, pecan, gum, persimmon, maple, cherry, and a few other hardwood species. The larvae are found in hardwood flooring, furniture, picture frames, and trim.

Anobiid and cerambycid beetles lay eggs in crevices on the surface of the wood; cerambycids also lay eggs in emergence holes.

Bostrichid beetles that bore into seasoned hardwoods often bore chambers at the sides of their tunnels and lay eggs in them.

Unseasoned hardwoods.--Bostrichids that infest green and seasoning hardwoods lay eggs in pores leading from the entrance tunnels. The red-shouldered shothole borer is one of these. Bostrichids frequently attack bark-covered wood. They usually do not reinfest the wood from which they emerge.

=Infestations in Softwoods=

Seasoned softwoods.--Some kinds of beetles infest seasoned softwood lumber used in the structure of buildings.

Certain of the bostrichids require bark for egg laying. They infest lumber that has bark on the edges. Such lumber is often used in framing, subflooring, and roofing. The females lay eggs in the bark. The larvae of some species complete their development in it; others go to the adjacent wood to do so. The adult females may reinfest the wood from which they emerge.

Other beetles that infest seasoned softwoods do not require bark for egg laying. Among them are the old house borer and the cossonid weevils. The females lay eggs in crevices in the wood. They may infest the same wood repeatedly.

The old house borer infests framing and subflooring. It is found in old and new construction and in stored lumber. Cossonid weevils are found in pine flooring, baseboards, wall stops, and roof trusses.

Unseasoned softwoods.--The beetles that infest green and seasoning softwoods include several cerambycids--for example, the black-horned pine borer--and a few bostrichids. Most of these beetles require bark for egg laying. The adult females usually do not reinfest the wood from which they emerge; they seek other unseasoned wood and lay eggs in the bark.

=Infestations in Bamboo=

Certain species of bostrichid, cerambycid, and lyctus beetles infest bamboo products such as furniture. Venetian blinds, draw drapes, baskets, fans, and fishing poles.

Plant-quarantine inspectors at United States ports of entry often intercept the beetles in bamboo products imported from the Far East. Among the beetles intercepted are the bamboo powder-post beetle, a bostrichid, and the bamboo borer, a cerambycid. These beetles and the lyctus beetles may reinfest the material from which they emerge.

DAMAGE

Part 3

The increase in building activity that followed World War II brought the destructiveness of powder-post beetles to widespread attention. The more buildings, the more damage.

The old house borer is rapidly spreading over the eastern half of the United States, and is found more and more in lumber used in new construction. It is becoming one of the most serious pests of wood in buildings.

Powder-post beetles damage wood by tunneling and by cutting surface holes.

Tunneling is done by the larvae of all kinds of powder-post beetles, and by adult bostrichids and cossonid weevils. The larvae of anobiid beetles leave elongate pellets of excreted wood in their tunnels. Other larvae leave powderlike borings. Severely damaged wood becomes a crumbly mass of pellets or of borings, and sometimes has a honeycombed appearance.

Since the insects do most of their tunneling in sapwood, structural damage is rare in large timbers.

Surface holes mar the appearance of wood. Those most commonly seen are made by adult beetles when they emerge from the wood. Those made by many of the smaller beetles are about 1/8 inch in diameter. They give wood the appearance of having been hit by buckshot, and are called shotholes. Larger beetles make holes 1/4 to 3/8 inch in diameter.

Continue reading Powder-Post Beetles in Buildings: What to Do About Them free in the Wunder reader →