Drywood Termites in California: The Hidden Threat in Your Walls

If you live in California — particularly in Southern California, the Bay Area, or coastal regions — there's a good chance drywood termites have already established themselves somewhere in the wood structure of your home. The western drywood termite (Incisitermes minor) is the most common wood-destroying pest in California, infesting approximately 1 in 5 structures in the southern part of the state.

What Makes Drywood Termites Different

Unlike the subterranean termites that dominate in the Eastern US and Texas, drywood termites don't require contact with soil or moisture. They colonize dry wood directly — infesting:

• Roof framing, rafters, and attic structure
• Window and door frames
• Hardwood floors
• Furniture (including antiques)
• Garage door framing
• Any exposed dry wood in or around the home

Drywood termite colonies are smaller than subterranean colonies (typically 2,000–3,000 individuals vs. millions for Formosan) but multiple simultaneous infestations in different parts of the same structure are common. Their damage accumulates slowly over years — which is why a WDO inspection is required by most CA lenders at home purchase.

Treatment Options: Fumigation vs. Spot Treatment

Whole-structure fumigation (tenting): The most thorough and reliable treatment. The entire structure is enclosed in a tent and filled with sulfuryl fluoride (Vikane) gas at a concentration lethal to termites throughout. Penetrates wood, wall voids, and all areas of the structure. Requires vacating the home for 2–3 days. Eliminates all active infestations but provides no residual protection — re-infestation can occur.

Cost: $1,500–$4,000 for a typical California home depending on size and fumigation company.

Spot treatment: For localized, accessible infestations. Licensed CA Branch 2 PCOs can treat individual infested areas with:

• Orange oil (d-limonene): Injected into galleries; lower toxicity option; effective for accessible, localized infestations
• Borates (Tim-bor, Bora-Care): Applied to bare wood; protects against future infestation; commonly used in new construction and during remodels
• Electro-gun / microwave: Localized heat or electrical treatment to infested areas; no chemicals but limited penetration
• Freezing: Liquid nitrogen applied to infested areas; chemical-free; effective for accessible areas

Spot treatments are appropriate for limited, confirmed infestations in accessible areas. For widespread or inaccessible infestations — particularly in attics, wall voids, or subfloor — fumigation is generally recommended by licensed inspectors.

WDO Reports and California Home Sales

The California Wood Destroying Organism (WDO) inspection — colloquially called the "termite report" or "Section 1/Section 2 report" — is required by virtually all lenders and is standard in most real estate transactions.

• Section 1: Active infestations and conditions directly caused by wood-destroying organisms. Sellers are typically required to address Section 1 items before close of escrow.
• Section 2: Conditions that are not actively infested but could lead to infestation (excessive moisture, wood-to-soil contact, etc.). Buyer and seller negotiate responsibility.