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How Serious is An Old House Borer Infestation in a Home?

By Chris Williams on May 13, 2016.

Old house borers are wood-infesting beetles that sometimes show up in homes. Infestations usually begin in newly cut wood, even before the wood is incorporated into a home. Female beetles lay their eggs in cracks in softwoods such as pine, fir, or spruce, often while it is stacked in lumberyards.

Because only certain boards are infested during storage or construction, old house borer infestations tend to be localized and limited to a few boards in a home. Infestations can be found anywhere in a new structure, including walls, attics, basements, or crawlspaces. In our Northeastern region, old house borers seem to be most common in attic framing.

Emergence of Adult Beetles Can Take Years

Old house borer larvae feed and grow inside the wood for 2 to 15 years, depending on conditions. Larvae develop to adults more rapidly in southern states, and in structures that are heated year-round, and in wood with a higher moisture and protein content. In the Northeast, larval development usually takes 5-8 years. So even though the larvae may have been “built into” a new home, by the time adult beetles emerge many years later, they are literally “old house” borers. See also Old House Borers” Infest New Houses.

After mature larvae have pupated, one inch long gray beetles (see Have an Old House Bore? for photo) exit the wood in mid to late summer in the Northeast, pushing powdery sawdust out of the oval emergence holes as they exit.

Damage May be Limited Unless Beetles Reinfest Wood

Because old house borer larvae are large and feed for years, they can do considerable damage as they hollow out galleries inside wood, but the damaged area is usually limited. That’s true for the first generation of beetles, when they first emerge in a home that is less than 10 years old. Unfortunately, old house borers can reinfest other softwoods in a home if conditions are right and then damage can be considerable with overlapping generations over many years.

In most cases, old house borer infestations are limited to a single generation. Reinfestation doesn’t often happen and occurs most often where there is excessive wood moisture (15-25%). Attics with leaky roofs or basements or crawlspaces are the most common reinfestation sites.01

The amount of damage that old house borers can do in a home depends on (1) the extent of the infestation (a couple of boards or most of the attic framing?), (2) the larval growth factors present such as temperature and humidity, and (3) whether conditions in the home will allow reinfestation. A professional exterminator can answer these questions with a thorough inspection and help determine what action to take. Control may be doing nothing, removing and replacing infested wood, spot treatments, or fumigation.

Photo Credit : “130312 Tesarik krovovy Hylotrupes bajulus (5)” by svajcr | CC BY-SA 3.0 via Wikimedia Commons.

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