The adult lyctid powderpost beetle is a small (3/32 to 1/4 inch-long), cylindrical, brown beetle that attacks hardwood. Damage caused by the powderpost beetle is usually first detected with the appearance of holes in wood, 1/32 – 1/16 inch-diameter, from which a very fine sawdust may fall. Larvae of the powderpost beetle feed on many of the various hardwoods used in furniture, baskets, hardwood trim and flooring. Infestations in homes are almost always due to infestation of the wood prior to construction.
Powderpost beetles pass through four distinct life stages: egg, larva, pupa and adult. The first three of these stages are found only in the infested wood. The larva is a creamy white, C-shaped grub with an enlarged thorax. The larval stage of the beetle is responsible for most of the actual feeding damage to the wood.
Outdoors, the life cycle of a powderpost beetle normally requires about a year; however indoors, powderpost beetles may require two or more (possibly up to five) years to complete their development and emerge from the wood. For this reason, infestations may not be detected for several months, or even years, after completion of a new home.
The most commonly infested woods include ash, oak, hickory and walnut. Although powderpost beetles pose little threat to the structural integrity of most homes (which are framed with softwood lumber, thus not susceptible to attack), it is a reportable wood destroying beetle and can affect property resale value. It is also possible, though unlikely, that such an infestation could spread to hardwood furniture, trim, paneling, or flooring if left untreated.
Female beetles emerging from infested wood search for a mate, and then lay their eggs on a suitable piece of wood. Powderpost beetles usually require unfinished wood (no paint or varnish coating the wood pores) in which to lay their eggs. However, the most common site for egg-laying indoors appears to be exit holes from which the females have emerged. In this way beetles can re-infest finished wood. Infestations can also spread internally to adjacent wood as larvae chew their way from one piece to another.
The most economical control method is removal and replacement of infested wood pieces. Where damage is limited, this is the simplest and most practical solution. Removing infested wood and replacing it with uninfested (preferably treated) wood will eliminate the problem in most cases. It can be difficult, however, to know whether all infested wood has been removed.
Painting infested wood surfaces with a pesticide labeled for such use is another option. Before painting infested wood with a residual insecticide, all infested wood must first be stripped of paint or other finishes. Treatment is then applied to the bare wood, and the wood refinished. This treatment does not kill beetles that are in the wood–rather it kills adult beetles as they emerge. Eliminating an infestation in this way can take several years. Should you decide to sell your home during that time, you would be unable to assure the buyers that beetle emergence has been eliminated.
Another option is to inject infested wood with an insecticide. Injections are usually made using a pressurized spraying system and typically use borate salt solutions. Injection may be a practical treatment for isolated infestations that cannot be easily corrected by wood removal.
Perhaps the surest method for controlling powderpost beetles is fumigation. Fumigation is a costly and inconvenient procedure that involves placing a gas-tight tent over the entire home and injecting a gas that is capable of penetrating wood and killing beetles. Two or more days are then required to air the home adequately before it can be re-occupied. Treatment costs can easily reach ten thousand dollars or more for a moderately sized home. For a property owner who requires a guarantee of complete elimination, or where infestations are widespread and untreatable by other methods, this is sometimes the only viable option.
For more information
For more information on lyctid beetles and other structural infesting wood beetles, request publication E-394, Structure Infesting Wood Beetles.
Michael Merchant, Ph.D., Professor and Extension Urban Entomologist, Texas AgriLife Extension Service.