Ants in the house: Argentine ants, baits vs. sprays and when to call a pro
For Silicon Valley homes · Updated October 2026 · Sources below
The Argentine ant is the most common ant in and around California homes, and it moves indoors when weather turns very wet or hot and dry. Baits work far better than sprays: sprays kill only the foraging ants, while baits are carried back to the colony and the queens. Clean up the trail, seal the entry point, and set baits outside.
The short version
- Argentine ants are California's most common house ant
- They move in during heavy rain and during hot, dry spells
- Baits, not sprays - sprays leave the colony and queens alive
- Don't spray where you're using baits
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What it costs
- Ant treatment$80 - $500
Typical ranges from published cost guides - mostly national figures. Bay Area prices usually run higher. Your actual price depends on your home and the job, and a pro gives you the real number. Source: HomeAdvisor cost guide (national) (Jun 2026). Have a quote? Check it with the Quote Explainer
Signs of an ant problem
- Trails along counters, baseboards or window sills
- Ants around pet food, sugar or the sink
- Ants coming in at the same crack or gap
- Ants climbing plants near the house (they farm aphids for honeydew)
What to do first
- Wipe up the trail with soapy water or window cleaner, and remove what attracted them.
- Caulk the crack they're coming through, or plug it with petroleum jelly as a quick fix.
- Set bait stations outside along the foundation and at nest openings, every 10 to 20 feet.
- Trim branches and plants so they don't touch the house, and keep mulch a few inches from the foundation.
- Call a pest control pro trained in IPM if ants keep coming back after these steps.
In Silicon Valley
- UC IPM: the Argentine ant is the most common ant in and around homes and gardens in California.
- Argentine ants move indoors seeking refuge from flooded conditions or hot, dry weather, so invasions often come with a change in the weather. UC IPM suggests caulking and baiting before the yearly influx.
- UC IPM says treatments in late winter and early spring, when colonies are just starting to grow, are the most effective.
Questions homeowners ask
Why are ants coming into my house when it rains?
Argentine ants move indoors to escape flooded soil, and also during hot, dry spells. They also show up suddenly when their outdoor food runs short.
What's the best way to get rid of ants in the house?
Clean up the trail, remove the food, seal the entry point, and use baits outside. UC IPM says baits are more effective and safer than sprays, because worker ants carry the bait back to the colony.
Should I spray around my foundation for ants?
It usually doesn't last. A perimeter spray kills only the foraging ants, the colony and queens survive, and ants soon return - and sprays can even trap ants indoors. Don't spray where you're using baits.
Which ant bait works best?
For Argentine ants, sweet baits work year-round. Slow-acting liquid baits with a low borate content (about 0.5 to 1%) in refillable stations tend to affect the colony more than small prepackaged stations, but results can take several days to a week.
When should I call a pest control company for ants?
If ants keep coming back after you've cleaned, sealed and baited, UC IPM suggests hiring a pest management professional trained in IPM. They have access to more effective materials and equipment.
How much does ant control cost?
See the typical range from HomeAdvisor's national cost guide on this page. One-time treatments and ongoing service plans are priced differently, and Bay Area prices usually run higher.
Save with your neighbors
Ant & pest treatment is a job neighbors team up on: one pro, one trip down your street, a group price the pro sets. Three homes start it.
Start or join a Neighborhood Block DealQuestions to ask the pro
- Do you use baits, sprays or both - and where?
- Is this a one-time treatment or a service plan?
- Are your products safe around kids and pets?
- What should I do, and not do, between visits?
- Do you follow integrated pest management (IPM)?
Before you sign, check the contractor's license at cslb.ca.gov. How to hire a contractor in California
Need a pest control pro?
Tell us about the job in 2 minutes - free. We send it to one local pro at a time, never a crowd.
Related answers
Sources
General information for Silicon Valley homeowners, not professional advice for your home. Rules and programs change - check the source, and have a licensed pro look at your situation.