How To Recognize Structural Wood Damage Inflicted By Deathwatch Beetles

When asked to name a group of insect pests that infest structural wood within homes and buildings, most people would immediately mention termites, and some may mention carpenter ants, but few would be able to name others. It is well known that termites consume wood, and given the relatively high rate of black carpenter ant infestations in the northeast US, many residents of upstate New York, particularly homeowners, are aware that carpenter ants infest wood for nesting purposes. However, there are many other destructive insect pests that nest and feed within structural wood sources, including powderpost beetles, old house borers, and false powderpost beetles.

Another wood-boring insect pest species, Xestobium rufovillosum, is native to Europe, but they have become well established in the northeastern US, including upstate New York. This species is more commonly known as the “deathwatch beetle,” and it is notable for infesting hardwood structural lumber as well as finished wood sources, most notably furniture.

The 7 mm long reddish-brown Adult female deathwatch beetle deposits numerous eggs within cracks, crevices and pores on the surface of hardwood, particularly oak and chestnut. Eventually, 11 mm long yellowish larvae emerge from these eggs and bore into hardwood, where they excavate nesting galleries and feed on partially digested wood until they reach maturity, which can take one year or as many as ten years, depending on internal and external environmental conditions. Unlike termites, deathwatch beetles can only consume wood that has been partially predigested by fungi.

Given their habit of consuming wood sources that have become compromised by fungi, these beetles generally infest structural wood sources located in excessively moist indoor areas where fungi has developed. For example, wood located within floor and wall voids in bathrooms, kitchens and laundry areas often become infested with deathwatch beetle larvae, and they are frequently found infesting wood that has become waterlogged due to being exposed to rainwater or plumbing leaks.

Another common deathwatch beetle species in upstate New York, the “eastern deathwatch beetle,” commonly infests ash, basswood, maple, beech, and elm wood sources that make up sills, joists, beams and flooring, often resulting in extensive damage. Infestations are difficult to notice, but once larvae develop into adults, they take flight from small 3 mm wide exit holes that can be found on the surface of formerly infested wood sources.

Have you ever discovered exit holes on the surface of structural or finished wood sources within your home?