What is the difference between subterranean and drywood termites in San Diego County?

Two very different insects

Homeowners tend to say termites as if it were one thing. In coastal Southern California it is at least two, and they behave differently enough that the inspection, the treatment, and even the carpentry repair change depending on which one you have.

Subterranean termites nest in the soil, where they get the moisture they need, and come up to feed. Drywood termites live their whole lives inside a piece of wood, drawing what little moisture they need from the wood itself and the humid coastal air. Both are common in Carlsbad, Oceanside, Encinitas, and inland North County.

Subterranean termites: the ones that come from the ground

Look for mud tubes. These are pencil-width to finger-width tunnels of soil and saliva that climb foundation walls, piers, posts, and the inside of crawl spaces. They let the termites travel from the soil to the wood without drying out. Break one open and you may see pale workers inside.

Damage is usually low on the structure: sill plates, the bottoms of posts, deck framing near grade, fence posts, stair stringers. The galleries follow the soft grain of the wood and are packed with mud. The wood often looks layered, like a honeycomb of paper-thin sheets. Because the colony is in the ground, treating the wood alone does nothing. The soil or the colony has to be treated, which is work for a licensed pest control operator.

Drywood termites: the ones that live in the wood

Look for pellets. Drywood termites keep their galleries clean by pushing waste out through tiny holes, and the pellets pile up below like coarse sand or coffee grounds. They are hard, six-sided, and about the size of a poppy seed. Finding a fresh pile is the most common way homeowners discover them.

Drywood colonies can be anywhere: attic framing, fascia, window trim, exposed beams, pergola rafters, furniture. They do not need ground contact, which is why a pergola or a second-story balcony can be infested with no sign at the foundation. Galleries cut across the grain and feel smooth inside. Treatment depends on how widespread the colonies are, from localized treatment of a few members to whole-structure fumigation, and that judgment is the pest inspector's to make.

Why the distinction changes the repair

With subterranean termites, our carpentry repair is only as good as the soil treatment and the moisture correction under it. We also look hard at why wood was close enough to the ground to be reached: posts set in soil, grade built up against siding, a deck with no clearance. Fixing that is part of the job.

With drywood termites, the question is how far the damage runs inside members that look fine on the surface. We probe and sometimes open up adjacent wood before deciding what to replace. If fumigation is planned, we schedule the wood repair after it, so new material is not installed into a structure that is about to be tented and opened up.

• Mud tubes, low damage, soil-packed galleries: subterranean
• Pellet piles, kick-out holes, clean cross-grain galleries: drywood
• Either way: pest inspection and treatment first, carpentry second

Who does what

In California, inspecting for and treating wood-destroying insects is regulated work done by companies licensed through the Structural Pest Control Board. Levi is a craftsman, not a pest operator; he repairs and rebuilds the damaged wood after the insects have been addressed and will tell you plainly if what he finds looks like active insect activity. The inspection report also becomes a useful map for scoping the carpentry, because it lists every location the inspector found.

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