Q: We recently removed the carpet in one room of our house.  The company that put in the new hardwood flooring did a great job matching the new floor with the existing one.   Three coats of finish were applied and sanded between each coat, with a final gloss buff-out included.   It looked fantastic and we were very pleased.  About 6 months later my husband notice what looked like little pin holes in one area. We moved all the furniture and area rugs and took a closer look.  There were actually two small areas with these tiny pinholes, on different sides of the room.  No insects have been noted in that room, or anywhere for that matter.  We are concerned that whatever it is could damage other areas of the floor or the structure of the house itself.

A:  As an Entomologist and a Pest Control Technician, I have some good news for you!  The most likely culprit is the Powder Post Beetle, but do not be alarmed.  Although powder post beetles can cause serious damage, the conditions have to be just right.  Let me discuss powder post beetles briefly, and then I will get back to your floor.

There are three families of beetles that are considered Powderpost beetles: Lyctids, Anobiids, and Bostrichids (false powderpost beetle). Within each family are many distinct species, each with its own range, habitat preference, and favored types of wood.

Lyctids, or True Powderpost Beetles, are by far the most common powderpost beetle associated with damage in North America.  Adults are very small, reddish to dark brown insects with a clearly visible head and antennae. Adults emerge, mate, and lay eggs in pores or cracks on the wood surface. The tiny worm like larvae create a very fine, talcum powder like frass as they feed on starches and sugars within various hardwoods like maple, oak, ash, and chestnut during development.  Once pupation occurs, adults bore out of the wood surface creating small shot holes, and a fine powder around the exit opening.  Lyctid beetles can have 2 generations per year in warmer zones, or may take several years to reach adulthood in zones that are more temperate. Many generations of beetles can infest the same piece of wood over time.

Anobiid powderpost beetles also damage wood that they infest.  Commonly known as “Deathwatch Beetles”, Anobiid beetles are the second most common powderpost beetle in North America.  Adult Anobiid beetles differ from Lyctids in appearance.  They are also very small (1-7mm), dark reddish to black, but their heads are directed downward, hidden by the rounded pronotum.  Larvae are also small and wormlike.  Lyctid and Anobiid larvae can be distinguished by distinct characteristics.  After emerging in the spring, mating takes place and females lay eggs in cracks, crevices, or just inside old emergence holes.  As larvae feed, they pass the lignin and cellulose they cannot digest in the form of a gritty, packed frass (not as fine as Lyctid frass).  Anobiid beetles prefer older wood and have been known to infest spruce and pine products as well as hard woods. Anobiid infestations usually start in wood that has been wet periodically and may have or previously had fungal decay of some kind. In severe cases, almost all of the wood will have been consumed and structural failure can occur.  Although Anobiid damage occurs slowly, the underlying moisture issue may be evident and fixable.

“False Powderpost” beetles, the Bostrichids are a more prevalent problem in tropical regions.  Adult Bostrichids resemble Anobiids in body form, head oriented downward and in most cases, covered by the pronotum.  Some species are quite large in size compared to Lyctids and Anobiids.  Damage from Bostrichids can also be quite severe as both adult and larvae damage the infested wood.  Females bore into the preferred wood and create egg galleries, when the eggs hatch the larvae then feed on the wood.  Tunnels of different sizes packed with a gritty frass can be quite extensive, often rendering the wood structurally useless.  Some Bostrichids are attracted to heat and have been known to bore into lead cables, wires, asphalt roofing, and other warm objects in search of oviposition sites (the Lead Cable Borer).  With the ability to infest both hard and soft wood, Bostrichid damage can be severe if left untreated or addressed.

Control and management of powderpost beetle infestation revolves around controlling moisture levels within the structure.  Management strategies may include removal of infested members, structural changes to reduce conducive conditions (vapor barriers, gutters, drainage systems, sump pumps, grade changes etc.), dehumidification systems, air movement systems, and venting to name a few options.  Treatments made with various borate products may be an option in some situations, while topical finishes or other treatment may solve others.  Fumigation may be an option for whole building treatments.

Now back to the floor.  I have seen what you described many times.  New flooring is installed and finished, and then months or even years later, small holes develop.  These are emergence holes made by adult beetles leaving the wood.  Most hardwood floors have been dried and aged, but were part of a tree, and then board at one time. Since PPB only lay eggs in dead wood, the egg may have been laid in the mill or lumberyard, or in storage.  Once the wood planks are shaped into actual flooring, the egg, or larval beetles may remain in the wood and finish their slow development.  Depending on the species of beetle and the type and condition of wood involved, the duration of development may vary greatly.  Once the adult beetles emerge inside your home, the will find few or any partners to mate with, and will be unable to lay egg on the finished surfaces of your flooring.  Re-infestation is highly unlikely.  The reason the holes were in two distinctly different areas is because the plank that had the beetle larvae was used to make several of the individual flooring boards, but they were placed in different areas of the room.  As you can see, not all of the boards have the pinholes, only two actually.  One way to check for activity is to place a piece of tape over area of concern.  If beetles are emerging, there will be holes in the tape.  If no activity is noted, a little sanding and finish work will hide the holes.  The rest of your home is not at risk.    In any case involving Pest Control, it is always best to call a Pest Control Professional.   For safe and effective management solutions to any pest control problem call the Professionals at Colonial Pest Control Inc. 1-800-525-8084.

Tim Chace

12/29/2015