Finding a small pile of what looks like sawdust on your windowsill, or noticing a mud-colored tube running up your foundation wall, raises an immediate question: what kind of termite is this, and does the answer actually matter? After 17 years of termite work across San Mateo neighborhoods, we can tell you it matters more than most homeowners expect. The wrong treatment does nothing at all for the species you actually have.
San Mateo sits in a region where the housing stock, coastal moisture, and soil conditions create near-ideal conditions for termite activity. The county has some of the oldest homes in the entire Bay Area, and termites appear frequently on pest inspection reports when properties change hands. Understanding what you’re dealing with before anyone applies a single treatment is the difference between solving the problem and spending money on the wrong solution.
Three Termite Species Live in San Mateo, but Two Cause Most of the Damage
The San Mateo County Mosquito and Vector Control District confirms that all three termite species found in California are present here: dampwood, drywood, and subterranean. Dampwood termites require very high moisture conditions. Typically found in decayed or water-damaged wood, they are the least structurally significant of the three. Most homeowners with a serious problem are dealing with either drywood or subterranean termites, and both are active throughout the county.
Subterranean termites are the most destructive species in California. A mature colony can number in the hundreds of thousands of workers and cause severe structural damage before any surface signs appear. Many San Mateo homes built before 1980 sit on crawl space foundations, and those crawl spaces create the moisture-rich, soil-contact environment that subterranean termites need to establish and expand. The older the home and the less managed the crawl space, the higher the risk.
How Drywood & Subterranean Termites Behave Differently
The two species are fundamentally different in how they live, which is why they require completely different treatments.
Drywood Termites
Incisitermes minor, the Western drywood termite, lives entirely within the wood it consumes. It needs no soil contact and draws no moisture from an outside source. Colonies are typically fewer than 1,000 individuals, and the damage they cause is slower and more localized. You’ll find them in attic framing, wall studs, window and door frames, hardwood floors, and even wooden furniture. Because the entire colony is contained within the structure, treatment can reach every individual.
Subterranean Termites
Reticulitermes, the Western subterranean termite, nests underground and must return to the soil to survive. Workers travel up into the structure through mud tubes. These pencil-width tunnels are built from soil and waste to protect the colony from open air. They enter through foundation cracks, plumbing penetrations, and any point where wood contacts soil. A large colony causes damage fast, and because foraging happens inside walls and framing members, the destruction is often well underway before anyone sees a single sign.
How to Tell Which Species You Have
A few physical signs point clearly toward one species or the other, though confirming the presence of either requires a thorough inspection of areas you probably can’t easily access yourself.
- Frass near wood surfaces: Drywood termites push their dry, hard fecal pellets (called termite frass) out of small kick-out holes in the wood. Frass looks like coffee grounds or fine sand and accumulates in small piles below infested wood. Subterranean termites don’t produce visible frass; they use their waste to construct mud tubes.
- Mud tubes on your foundation: Mud tubes running along concrete piers, foundation walls, or crawl space framing are a definitive sign of subterranean termite activity. Their absence doesn’t rule them out, since some tubes run inside walls where you can’t see them.
- Swarmer alates near windows or lights: Both species produce winged reproductives at certain times of year. In San Mateo County, drywood termites swarm in summer and fall, while subterranean termites swarm after the first fall rains. Discarded wings near windows or light fixtures during either of those periods is a strong signal that a colony is somewhere in or around your home.
Why Species Identification Determines Treatment
The treatment approach for each species isn’t just different. Applying the wrong one is completely ineffective.
For drywood termite infestations, a limited problem can often be handled with localized spot treatment. If activity is widespread across multiple areas of the home, whole-structure fumigation is the standard recommendation. Fumigation works for drywood termites because the entire colony lives inside the structure, and the gas reaches every corner of every wall cavity and framing member.
Fumigation does nothing for subterranean termites. Because the colony lives in the soil outside the structure, gassing the house leaves the source completely untouched. Subterranean infestations require either a liquid soil barrier treatment applied around the perimeter and under the foundation, or a bait station program such as the Sentricon system, which carries a slow-acting agent back to the soil colony. A Wood Destroying Organism (WDO) report is a formal inspection document commonly required in California real estate transactions. It identifies both species when present and provides the documentation needed to choose the right path.
Both species can be active in the same home at the same time, and this isn’t unusual in older Bay Area properties. A dual infestation requires sequential treatment: handle the drywood colony first, then address the soil colony separately. Getting an accurate identification before any treatment begins is the only way to know whether you’re dealing with one problem or two.
What San Mateo Homeowners Should Do Now
Some prevention steps are worth taking regardless of which species concerns you most. For subterranean termite risk, reduce or eliminate wood-to-soil contact around the foundation, address moisture issues in the crawl space, and keep wood debris away from the structure. For drywood risk, seal exterior cracks, gaps around window frames, and attic vents before late summer swarming season begins.
DIY termite products sold at hardware stores don’t reach established colonies of either species. They can also scatter the visible population without addressing the source, which makes professional treatment harder and more expensive afterward.
Annual professional inspections make particular sense for San Mateo homes with crawl space foundations or pre-1980s construction. Activity hidden inside walls and framing members requires thermal or moisture detection tools to locate. A walkthrough alone won’t find it. We use advanced inspection technology to find hidden termite activity and build the treatment plan around what we actually find.
Getting the species right is the first and most important step. Getting it wrong doesn’t just delay the solution; it wastes money and allows the colony to keep working. If you’ve spotted frass, mud tubes, discarded wings, or hollow-sounding wood anywhere in your home, Pacific Pest Management offers free estimates and same-day availability throughout San Mateo. Call us at (888) 506-3122 and we’ll take a look at what you’re actually dealing with.