The old house borer (Hylotrupes bajulus) is one of the most destructive wood-boring beetles in the United States, despite its misleading name — it attacks new construction as readily as old homes. This longhorn beetle (family Cerambycidae) is a serious pest of seasoned softwood lumber, particularly pine, spruce, and fir used in roof framing, wall studs, subflooring, and structural timbers. Adults are large (5/8–1 inch), grayish-brown to black, with two shiny black knobs on the thorax and grayish hair patches on the wing covers. Females lay eggs in cracks and crevices of bare softwood; larvae bore oval tunnels through the wood for three to ten years or more, producing a fine, tightly packed frass and making a distinctive rasping or ticking sound audible through walls. Exit holes are oval, about 1/4–3/8 inch wide. In Arizona, old house borers are found throughout the state and are a significant concern in new construction where infested lumber is used. Infestations can go undetected for a decade while larvae hollow out structural members.
👁Warning Signs
Oval exit holes (1/4–3/8 inch) in softwood lumber. Tightly packed, fine frass in tunnels. Rasping or ticking sounds from within walls or ceilings. Blistering or rippling of wood surfaces over larval tunnels. Large grayish-brown beetles near wood.
⚠Health & Property Risks
Severe structural damage to roof framing, wall studs, and floor joists. Long larval period (3–10+ years) allows extensive hidden damage. Can cause roof or floor collapse in heavily infested structures.
Prevention Tips
Inspect all new softwood lumber before use. Apply boron-based wood preservatives to bare structural lumber. Reduce attic humidity. Seal wood surfaces where possible.
🛡Professional Treatment
Professional inspection and treatment required. Boron-based preservatives injected into wood, surface insecticides, or fumigation for widespread infestations. Severely damaged structural members must be replaced.
Frequently Asked Questions — Old House Borer
The Old House Borer (Hylotrupes bajulus) is grayish-brown to black with two shiny thoracic knobs and gray hair patches and typically measures 5/8–1 inch. The old house borer (Hylotrupes bajulus) is one of the most destructive wood-boring beetles in the United States, despite its misleading name — it attacks new construction as readily as old homes. Thi.
Yes — the Old House Borer is considered a high-risk pest. Severe structural damage to roof framing, wall studs, and floor joists. Long larval period (3–10+ years) allows extensive hidden damage. Can cause roof or floor collapse in heavily infested structures.
In Arizona, old house borers are most often encountered in the following situations: Oval exit holes (1/4–3/8 inch) in softwood lumber. Tightly packed, fine frass in tunnels. Rasping or ticking sounds from within walls or ceilings. Blistering or rippling of wood surfaces over larval tunnels. Large grayish-brown beetles near wood.
The Old House Borer is most active during: Year-round in wood; adult emergence summer (June–August). Arizona's warm desert climate can extend activity periods compared to other states, so year-round vigilance is recommended in the Phoenix metro and surrounding areas.
Inspect all new softwood lumber before use. Apply boron-based wood preservatives to bare structural lumber. Reduce attic humidity. Seal wood surfaces where possible.
Professional inspection and treatment required. Boron-based preservatives injected into wood, surface insecticides, or fumigation for widespread infestations. Severely damaged structural members must be replaced.
Left unchecked, Old House Borer infestations can cause significant structural or food-storage damage over time. Severe structural damage to roof framing, wall studs, and floor joists. Long larval period (3–10+ years) allows extensive hidden damage. Can cause roof or floor collapse in heavily infested structures. Early detection and professional treatment are the most cost-effective approach — contact Pest Control Bros for an inspection at the first sign of activity.
Dealing with Old House Borer?
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