Harris County is home to two species of wood-destroying termites that together cause the majority of structural pest damage in Greater Houston: the native subterranean termite (Reticulitermes species) and the invasive Formosan subterranean termite (Coptotermes formosanus). While they share the same "subterranean" classification — both require soil contact and build mud tubes — their behavior, colony size, and treatment requirements differ significantly.
This article explains how to distinguish the two species, why Formosan termites are a growing concern in Houston's newer suburbs, and how treatment protocols differ depending on which species is present.
Native Subterranean Termites: The Species Houston Has Always Had
Native subterranean termites (Reticulitermes flavipes and Reticulitermes virginicus) have been present in Texas for millennia. They build colonies of 60,000 to 300,000 individuals in soil, accessing above-ground wood through exploratory mud tubes.
Characteristics of native subterranean termites in Houston: - Colony size: 60,000–300,000 workers - Swarming season: February through April, daytime after warm rain - Swarmer color: Dark brown to black, approximately ¼ inch - Mud tube diameter: Pencil-thin (⅛–¼ inch) - Damage rate: Slow — a mature colony consumes approximately 5–7 feet of 2×4 lumber per year - Distribution: All of Harris County and surrounding areas
Native subterranean termites prefer wood with high moisture content. They are attracted to wood-to-soil contact — siding that touches soil, wooden porch supports resting on dirt, and debris lumber left against the foundation. They also invade through expansion joints in slab foundations.
Formosan Subterranean Termites: The Invasive Species That Is Changing Houston's Risk Profile
Formosan termites (Coptotermes formosanus) arrived in the continental United States via infested ship cargo and have established in Houston over the past 30+ years. They are the most aggressive wood-destroying insect in the country.
Characteristics: - Colony size: 1 million to 10+ million workers - Swarming season: April through June, evening (dusk), attracted to lights - Swarmer color: Yellowish-brown with translucent wings, slightly larger than native species - Mud tube diameter: Thicker — up to ½ inch wide, sometimes resembling water-damaged sheetrock - Damage rate: Fast — a mature Formosan colony can cause severe structural damage within 6–12 months - Distribution: Concentrated in Houston's inner loop, older suburbs, and areas near ship channels
Formosan termites can build aerial colonies (carton nests) inside wall voids, attics, and crawl spaces without maintaining continuous soil contact — a behavior that makes them harder to treat with standard liquid termiticide barriers alone. These carton nests are made of chewed wood, saliva, and soil, and retain moisture that allows the colony to survive away from ground soil.
How Treatment Differs Between Species
A TPCL-licensed technician determines the species during inspection because treatment protocols differ:
For native subterranean termites, a continuous liquid termiticide barrier (Termidor or equivalent) applied around the foundation is typically sufficient. The barrier must be unbroken — any gap allows termites to enter. Bait systems such as Sentricon are also effective and may be preferred when drilling is not feasible.
For Formosan termites, combined treatment is often required: liquid termiticide at the foundation PLUS bait stations at strategic locations to target the colony directly. Formosan colonies are too large and their foraging territory too extensive for barrier-only treatment in some cases. The bait's delayed-action toxin must reach enough individuals to collapse the colony.
Formosan termites in attics or wall voids (aerial colonies) require targeted void treatment in addition to soil treatment — the technician injects termiticide into the void space to kill the carton nest directly.
Which Houston Neighborhoods Are at Highest Risk
Native subterranean termites are present everywhere in Greater Houston. However, Formosan termite concentration is higher in:
- The Inner Loop (Heights, Montrose, River Oaks, Midtown) — older construction with extensive mature landscaping
- The Ship Channel corridor (Pasadena, Baytown, La Porte) — suspected entry point for the species
- Older developments along Buffalo Bayou and White Oak Bayou
- Areas near railroad corridors where the species may have spread from infested railroad ties
What This Means for Houston Homeowners
The takeaway is not that Formosan termites are unstoppable — they respond to the same treatment methods when applied correctly. The difference is that Formosan infestations require more aggressive treatment, larger bait station coverage, and more frequent monitoring. Annual WDI inspections are especially critical in areas where Formosan termites are established.