Ant Control in San Carlos, CA

Local Context

Two Ant Waves a Year, Both Set by the Creeks and the Rain

Argentine ants on the Peninsula are unicolonial. Nests do not fight each other, workers move freely between them, and each nest carries multiple queens — so what looks like a colony in your planter bed is one node of something that runs the length of the block. In San Carlos they nest shallow: under slab edges, beneath the concrete walkways that came standard on 1950s tract lots, in irrigation valve boxes, under bark mulch and in the warm gap behind a stucco weep screed.

The first wave is water. Most of the city's 18 to 20 inches of annual rain falls between November and March, and storms flood shallow nests along Pulgas Creek and Cordilleras Creek, the drainage that separates San Carlos from Redwood City, plus the flat blocks that drain toward the Bay. Ants appear in kitchens and bathrooms within a day or two of a real storm. The second wave is the opposite. By August the soil on the hill lots above Crestview Drive is dry, and the same colonies follow moisture indoors to dishwasher pans, sink traps, pet bowls and condensate lines.

This is why spraying the visible trail backfires. It kills foragers, leaves the queens, and repellent product can split a stressed nest into several — more trails a week later, not fewer. Slow-acting bait works the other direction: workers carry it back and feed it through the nest before it acts. Carpenter ants are the exception, nesting in moisture-damaged wood rather than soil — deck ledgers on the hill lots, crawl-space framing in the flats.