There are two defining characteristics of powderpost beetle infestations. First, small piles of the powdery sawdust will appear and reappear after cleaning, under, around or on top of infested furniture or lumber. Second, numerous small, round holes (1/16 inch diameter) appear on the wood surface. Only when the wood is broken open do you find the criss-crossing, powder-filled tunnels inside the wood.
Adult powderpost beetle females lay eggs into open pores and cracks of wood. These eggs hatch into tiny larvae that burrow through the wood creating sawdust-packed tunnels. After a few months to a year or longer the larvae transform to adults and the new beetles emerge through the small round holes in the wood surface.
Powderpost beetles are divided into two major groups depending on the specific type of beetle and the type of lumber they attack. True powderpost beetles attack the sapwood of freshly cut hardwoods such as oak, ash, hickory, walnut, mahogany and similar species. Damage is generally confined to the sapwood portions of lumber though damage may occur in heartwood.
True powderpost beetles rarely attack wood that is more that 5 years old. New lumber will support beetle growth and development but most true powderpost beetle infestations disappear on their own as the wood ages. Varnished and cured lumber is not attacked by these beetles, and softwoods such as pine, spruce and fir used for house framing, are not attacked.
The false powderpost beetles are a more diverse group. These beetles attack both hardwoods and softwoods. The damage is similar to that described earlier: the larvae live inside the wood and make powder-filled tunnels and the adults emerge, leaving small "shot holes" in the wood surface.
False powderpost beetles are most common in wood that is more than 10 years old. They prefer to feed in sapwood (the portion of the lumber from the outside edge of the tree) but may feed in all wood, especially wood left undisturbed in cool, moist locations. False powderpost beetles take 2 to 3 years to develop, so damage accumulates slowly, but over time, may turn the entire board or piece of furniture to dust!
Actions following discovery of powderpost beetles depend on the severity and extent of the infestation, area or items being attacked, treatment or repair expense and whether the infestation is still active.
The practical alternative is often to repair, replace or discard damaged wood. If new cabinets or floor boards have a few widely scattered holes, repair with wood filler may be all that is necessary. More extensively-damaged floor joists or furniture might be repairable, though sadly, many old pieces are so completely destroyed that discarding is the only choice. If salvage is practical the most important next step, especially if false powderpost beetles are involved, is to get the lumber or wooden item to a dry location and keep it dry.
In some cases it may be practical to employ a licensed and certified pest control professional to chemically treat the surface of infested wood with a labeled insecticide. These special insecticides are usually not readily available to the general public. Existing finishes such as paint or varnish must be removed prior to insecticide application. Fumigation of infested lumber or movable items is a possibility, but is usually not practical in Iowa.