Powderpost beetles comprise several species of wood-boring insects in the Lyctinae subfamily. Commonly found in the home, powderpost beetles are wood pests that damage wooden furniture and structures. As developing larvae, the insects feed on wood and leave behind a fine powder, thus earning their name. Found throughout Canada, powderpost beetles feed on some of the country’s most common woods, including maple, ash, oak, and pine.
Appearance / Identification
Adult powderpost beetles are tube-shaped and range from 3 to 6 mm in length. Colour varies from reddish-brown to dark brown, with some species appearing almost black. The head features a pair of short, clubbed antenna, which distinguishes the powderpost beetle from other beetles of similar size and shape. Equipped with two pairs of wings, powderpost beetle adults are strong fliers. Larvae are white, C-shaped grubs that are wider at the front end than the back.
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In nature, powderpost beetles inhabit the moist, dead wood of logs, tree limbs, and branches. Usually when found in homes, it is likely introduced with an infested wood or wood structure, such as joists, rafters, floors, and panelling, as well as finished wood products. The insects overwinter in wood and are largely inactive most of the year. Warmer weather in the spring and summer draws adult beetles out to mate.
As larvae, powderpost beetles derive starch, sugar, and protein from sapwood, a tree’s soft outer layer of wood just below the bark. Unable to process lignin and cellulose, the insects avoid any wood materials other than sapwood. The pests prefer wood with high moisture content, as lower moisture levels make the environment uninhabitable for larvae.
Life Cycle / Reproduction
Powderpost beetles undergo complete metamorphosis consisting of four lifecycle stages: egg, larva, pupa, and adult. In the spring, female powderpost beetles lay their eggs in the pores and tiny cracks and crevices in the surface of wood. The eggs hatch into tiny larvae that bore into the wood and feed on their surroundings for anywhere from two to twelve months. Larvae then reach the pupal stage, which lasts about two to four weeks. Development time depends on type of wood, moisture content of wood, and temperature; it may range from one to several years.
The insects reach adulthood in the springtime and emerge from wood through small exit holes. As full-grown adults, powderpost beetles generally live for another two to five weeks. Once the adults emerge, they can re-infest the same wood by laying their eggs on the surface again, and the cycle continues. Environmental conditions, like humidity and temperature, can shorten or prolong the development process. Usually, powderpost beetles produce one generation a year.
Problems Caused by Powderpost Beetles
Powderpost beetles typically damage products manufactured from sapwoods, like furniture, panelling, molding, and flooring. When adults emerge from wood, they puncture small holes in the surface, which can ruin the appearance of furniture, flooring, or panelling. As infestations continue, the number of exits increases, making the wood look riddled with holes. In addition to causing aesthetic damage, powderpost beetles can compromise the structural integrity of wood. As larvae feed, they bore into wood and turn the material into sawdust-like powder. Because the insects commonly reinfest the same piece of wood for generations, they can cause total destruction over time.
Detection / Signs of Infestation
The first indication of a powderpost beetle infestation is the appearance of numerous small holes on the surface of wood. These small holes are usually the size of a pencil tip, or 1 to 3 mm in diameter. The margins of the exit holes from active infestations are often whitish or the colour of the exposed, underlying wood; however, the margins of exit holes from inactive infestations are blackened or dull colour of the wood. Frass in or around the exit holes further reveals an active infestation with the presence of adult powderpost beetles. The consistency of the frass helps to determine the specific type of beetle present in the wood. True powderpost beetle frass is light and powdery, whereas the frass produced by other beetles is grainy.
Most powderpost beetles enter the home inside of lumber or finished wood products, like furniture, ornaments, or panelling. Old, untreated wood is most vulnerable to a powderpost beetle attack. The largest powderpost beetle infestations usually result from using wood that was improperly stored outdoors. This typically occurs when individuals use old wood from barns or woodpiles in DIY projects. As a rule, homeowners should never use outdoor wood for indoor purposes.
When purchasing furniture or other wooden objects, ensure the pieces are made with kiln-dried wood or wood that has been sanded and varnished. For further protection from powderpost beetles, apply paint, shellac, or varnish to any untreated wood in the home. Powderpost beetles require the moisture level of wood to be above 12%. Introducing moisture barriers into the crawlspaces of infested structures may therefore help prevent the occurrence of a powderpost beetle infestation. Unfortunately, no method of powderpost beetle prevention is guaranteed or foolproof because the pests can still enter the home undetected inside of professionally stored and cured lumber.
Control / Removal
Infestations limited to a single object or a small area can be eliminated by removing the infested wood. If exit holes continue to appear in other areas, then additional control is necessary. Homeowners may use a number of insecticidal treatments, which can be applied to the surface of exposed wood. However, insecticides have limitations as they might not penetrate deep enough to kill the burrowed larvae. Surface treatment with insecticides that have residual effects will help to control reinfestation as it kills the adult beetles as they emerge from the wood. Formulas that include borates are especially effective because they penetrate wood to kill the larvae dwelling inside. If infestations persist after using insecticidal treatments, call a pest management expert. Pest control professionals can effectively manage and control powderpost beetle populations and take the necessary precautions to prevent infestations from recurring.
Pictures of powderpost beetles.