Pest Control in Round Rock, TX: Why I-35 Splits the City's Pests in Two

Short answer: Round Rock sits right on top of a geological fault line, and Interstate 35 runs almost exactly along it. West of I-35 you're on Hill Country limestone, where striped bark scorpions and spiders rule. East of I-35 you're on deep Blackland Prairie clay, where red imported fire ants and subterranean termites take over. That's why a neighbor on one side of town can battle scorpions all summer while a friend two miles east never sees one — and it's why effective pest control in Round Rock starts with knowing which side of the highway you're on. Root Home Services treats both, with local technicians who already know the pattern. Call (512) 222-5423 for a free quote.

Round Rock isn't one pest market — it's two, stacked back to back along the same interstate. Here's how the divide works, what it means for your home, and how to treat each side.

Why does one side of Round Rock have scorpions and the other has fire ants?

Because the two sides of town are built on completely different ground.

Round Rock straddles the Balcones Escarpment — a major fault zone where the Texas Hill Country drops down to the Gulf Coastal Plain. According to the Texas State Historical Association and University of Texas geologists, the fault juxtaposes hard Lower Cretaceous limestone on the west against deep clay, marl, and chalk on the east. In Round Rock, that boundary runs roughly along I-35:

• West of I-35 — hilly, "karst-like" terrain with thin, rocky topsoil over limestone. This is the edge of the Edwards Plateau / Hill Country.
• East of I-35 — flat, fertile Blackland Prairie with deep, dark clay soils that old-timers still call "black waxy" for their high clay content.

Pests don't read maps, but they absolutely respond to geology. Limestone gives scorpions endless cracks, ledges, and foundation gaps to shelter in. Clay holds moisture and gives fire ants and termites exactly the damp, diggable ground they need. Same city, same weather, two different problems — divided by one highway.

That single fact is the most useful thing a Round Rock homeowner can know before booking treatment, and it's something no national call center is going to tell you.

The west side: limestone, Hill Country, and scorpions

If your home is west of I-35 — think the rockier neighborhoods climbing toward Cedar Park, Brushy Creek's west end, and the Hill Country fringe — your signature pest is the striped bark scorpion (Centruroides vittatus).

Texas A&M AgriLife Extension reports that of the roughly 18 scorpion species in Texas, the striped bark scorpion is by far the most common and the one Central Texas homeowners actually encounter. It's a yellowish-tan scorpion up to about 2½ inches long, nocturnal, and a strong climber. Its sting is painful but rarely medically serious for healthy adults — more irritation than emergency.

Why it gets indoors on the west side:

• Limestone is honeycombed with harborage. Thin rocky soil, rock walls, and exposed bedrock give scorpions cool, dark daytime hideouts right up against your foundation.
• They follow gaps and moisture. Scorpions slip in through weep holes, gaps around plumbing penetrations, door sweeps, and rooflines, and they're drawn to moisture — which is why people find them in bathrooms, kitchens, and utility rooms.
• Summer pushes them in. Activity climbs as temperatures rise from late March through summer; as the weather turns, they hunt for warmth inside the house.

The fix on the limestone side isn't a one-time spray — it's exclusion plus a perimeter band. AgriLife's own guidance is to treat around the foundation and up the exterior walls, and the durable wins come from sealing entry points, trimming harborage away from the structure, and keeping a treated barrier in place through the warm months. (For the full playbook, see our deeper guide on scorpion control across the Austin metro and our scorpions library page.)

The east side: Blackland clay, fire ants, and termites

Cross to the east of I-35 — Teravista, the flatter stretches of Forest Creek, and the neighborhoods running toward Hutto and Pflugerville — and the soil flips to deep Blackland clay. So does the pest pressure.

Red imported fire ants (Solenopsis invicta) love this ground. Texas A&M AgriLife notes that fire-ant mounds are typically 4 to 24 inches tall with no visible surface entrance, and that the worst working periods are usually April through July and again late September through October. The clay is the key: when heavy rain floods their tunnels, the colony rushes the queen and brood to higher ground and can throw up fresh mounds overnight. That's why your east-side lawn can look clean on Friday and be dotted with mounds after a weekend storm.

The same moist clay is an open invitation to subterranean termites, which need ground-moisture contact and soft, diggable soil to tunnel up into wood. Texas subterranean termites swarm in spring — generally February through May — and the east-side clay gives them ideal conditions year-round. The danger is that they work silently inside the structure; by the time you see mud tubes on a slab or pier, they've often been active for a while.

The east-side approach is different from the west:

• Fire ants: a two-pronged treatment — broadcast bait the colony will carry back to the queen, plus targeted mound treatment — then a barrier so they don't keep rebuilding. Done with products applied to be safe for People, Pets & Plants.
• Termites: annual inspection is the real protection. Catching subterranean activity early, before it reaches framing, is what saves you from structural repair. See our subterranean termites and fire ants pages for the biology behind each.

Round Rock pest control: west vs east at a glance

	West of I-35 (Hill Country limestone)	East of I-35 (Blackland Prairie clay)
Ground	Thin, rocky soil over Lower Cretaceous limestone	Deep "black waxy" clay over shale, marl & chalk
Signature pests	Striped bark scorpions, spiders	Red imported fire ants, subterranean termites
Why this soil	Rock crevices = harborage; gaps & weep holes = entry	Moist clay = mound-building + easy termite tunneling
Telltale sign	Scorpions found indoors at night, under rocks/clutter	Fresh mounds after rain; mud tubes on the foundation
Treatment focus	Seal entry points + exterior perimeter band + de-clutter	Bait + mound treatment, termite monitoring, moisture control
Shared pressure	Mosquitoes (Brushy Creek), St. Augustine summer stress	Mosquitoes (Brushy Creek), St. Augustine summer stress

The point isn't that one side is "worse." It's that the right treatment plan depends on your ground — and a technician who knows the I-35 split walks up to your door already knowing what to look for.

What both sides of Round Rock share

Two pressures don't care which side of the highway you're on:

Mosquitoes. Brushy Creek, the area's many ponds, and shaded standing water keep mosquitoes active across Round Rock from spring through fall — and it's not just a nuisance. The Williamson County and Cities Health District confirmed the county's first human West Nile virus case of 2025 on July 3, 2025, and a mosquito trap sample collected at Brushy Creek tested positive for West Nile that season. Knocking down the shaded, standing-water breeding spots around your property is the lever that actually reduces backyard mosquito pressure.

Summer lawn stress. Round Rock's St. Augustine lawns get hammered by July and August heat on both sides of town. Brown patches in summer are usually heat-and-drought stress, chinch bugs, or brown-patch fungus moving in — problems that a recurring lawn program catches early, before a small patch becomes a dead one.

That's why Root runs both pest control and lawn care — one local team that already knows your soil can look after the whole property on coordinated visits.

How often should you get pest control in Round Rock?

Most Round Rock homes do best on quarterly pest control, with the season dialed in: heavier pressure during the summer surge, maintenance through the cooler months. Texas's long warm season lets scorpion, ant, and roach pressure rebuild fast, so the goal is to never let the protective barrier around the home fully lapse.

A practical Round Rock rhythm:

• Spring (Feb–May): termite swarm season on the east side; get the annual termite inspection in and re-establish the perimeter before summer.
• Summer (Jun–Sep): peak scorpion season on the west; peak fire-ant and mosquito activity everywhere. This is the heaviest-pressure window.
• Fall (late Sep–Oct): a second fire-ant flare-up; scorpions and rodents start seeking warmth indoors.
• Winter: maintenance — lower activity, but the barrier still matters for anything overwintering inside.

If pests show up between scheduled visits, a good local company comes back and re-treats at no charge. (Root does — there's no contract, you can cancel anytime, and re-treats between visits are free.)

Why "local" actually matters in a city growing this fast

Williamson County is one of the fastest-growing places in the country. New U.S. Census Bureau estimates reported by KXAN show the county added 23,814 residents between July 2024 and July 2025 — a 3.2% jump to 752,827 people, good for No. 9 in the nation by residents added and 42.8% of all the Austin metro's growth. A lot of those new homes are going up on both sides of the I-35 divide, often on freshly disturbed ground that scorpions and fire ants colonize quickly.

New construction is exactly when the soil-versus-pest pattern bites hardest — and exactly when a national call center, dispatching a stranger from out of town, is least likely to know that the home two streets over is on limestone while yours is on clay.

That's Root's whole wedge. We're family-owned and veteran-owned, six years in business with zero safety incidents, and rated 5 stars by 600+ Texas homeowners. Our technicians live in the same Williamson County neighborhoods they treat, so they already know the limestone-versus-clay split — and they treat your home for the pressure your side of town actually faces, not a one-size script.

Related: Scorpion control across the Austin metro · Common Texas pests · Pest & lawn care in Round Rock