Old house borers
Old house borer Hylotrupes bajulus (L.)
Larvae of the old house borer feed on seasoned softwoods and prefer the sapwood portions of pine, spruce and fir. Sometimes larvae are serious pests in modern log homes as well as conventional homes. Houses less than 10 years old are primarily attacked contrary to the name of old house borer. Full grown larvae can be heard boring in the wood, making a rhythmic ticking or rasping sound much like the sound of a mouse gnawing. In log houses, this sound may be heard from a distance of five to ten feet, day and night, at infrequent intervals. If the larvae work close to the surface, homeowners may find blistering of the wood, boring dust on surfaces below infested timbers, powdery borings in sapwood, oval emergence holes about 1/4 inch wide on the wood surface, larvae in tunnels or beetles in the building.
Adult old house borers are beetles 5/8 to 1 inch long, slightly flattened, brownish-black with many gray hairs on the head and thorax, two prominent black bumps on the prothorax and long antennae. The thorax (segment behind the head) has a shiny ridge down the middle and a shiny raised knob on each side, appearing as a face with a pair of eyes. Wing covers are marked with whitish spots that form two irregular bands or spots near the middle. Larvae are up to 1-1/4 inches long and have tiny ocelli (black eye spots) on each side of the head. They are flesh-colored, wedge-shaped (wider at the head), and segmented with legs present. Pupae are flesh-colored and about the size of the beetle. Eggs are white to grayish-white
The biology of the beetle's life cycle is greatly influenced by temperature, relative humidity and protein content of the wood. In Virginia, larvae require two to ten years to become fully grown and their feeding can cause extensive damage to infested wood. The adult stage is short, lasting eight to sixteen days, the egg stage about two weeks, the larval stage several years and the pupal stage two weeks. Under ideal conditions in many southern states, adults may appear after three to five years, sometimes remaining in larval tunnels for as long as 10 months before emergence. In more northern states, where humidity is low (as in some attics), an additional two to five years may be required to complete the life cycle. Adults emerge June, July and August with females attracted to dry, seasoned wood where eggs are laid reinfesting additional softwood. (Oils and resins in the heartwood portion of wood are undesirable.)
Log houses have become quite popular in many states. Many are made from pine trees (southern yellow pine and red pine), usually cut near the manufacturing site. Logs are partly or completely debarked before being cut into lengths and notched as part of a log house kit. These logs are strapped together and dipped into a preservative with the kit completed in a few days or weeks. Logs remain outdoors at the manufacturing site until the kit is complete. Then the entire house kit may be fumigated, loaded onto trucks and delivered to the construction site where logs may sit again before the homeowner assembles the house. The flight period of adult old house borers (June, July, August) may coincide at the manufacturing site or delivery site. If a log house kit produced during the fall is delivered to the building site, but assembly not made until spring or summer, any eggs laid in the cracks and crevices of the logs will hatch in only about nine days with the first stage larvae immediately penetrating the wood. Larvae may have gone below the depth of preservative treatment before being dipped. In about two years (four to five years in conventional lumber) larvae can be heard feeding below the log surface. Adult emergence holes are discovered easily. Reinfestation of log houses seems greater than conventional houses because of more exposed wood and the shorter feeding time of larvae.
Homeowners often ask when and where the logs became infested. However, it is impossible to determine precisely. One needs to know when the log house was manufactured, when it was delivered, when it was assembled, and when larvae were first heard feeding in the wood. To suspect that the infestation originated at the manufacturing site, all or part of the log house kit needed to be produced during the flight period of the female beetles. The larval feeding sounds and size of larvae removed from wood are helpful clues. Infestations may occur at the construction site when the kit remains unassembled. Infestations are known from Maine south to Florida and west to Michigan to Texas. The westward range extends approximately to the Mississippi River.
Ohio State University Extension Fact Sheet
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