The short version
Most termite problems in Ontario are desert subterranean termites, and the usual fix is a liquid soil treatment or bait stations, placed where the soil stays damp. Drywood termites need fumigation or wood treatment instead. Start with an inspection; $75–$250 is typical.
- Look for mud tubes, shed wings and hollow-sounding wood.
- Swarms usually show up from July through September.
- Drywood termites need wood treatment or fumigation instead.
- An inspection typically costs $75–$250.
- Insurance usually doesn’t cover termite damage.
Homeowners, landlords and anyone buying or selling a house in Ontario, whether you've spotted something or just want to know what to watch for.
What to look for
Spongy floors or bubbling paint usually mean long-running damage. So it's worth an inspection, even for one or two signs. Termites work quietly. A colony can feed inside a wall for years. Winters around Ontario stay mild, with average lows near 42°F, so colonies keep feeding all year.
- 1Screwdriver sinks easily into sills or trim.
- 2Discarded wings caught in spider webs.
- 3Mud tubes running up foundation walls or piers.
- 4Crumbling baseboards behind furniture.
- 5Piles of identical shed wings on windowsills.
- 6Blistered or bubbling paint on wood surfaces.
Why it’s worth acting soon
- Colonies grow and spread every year they go untreated.
- Damage hides behind drywall, flooring and trim.
- Homeowners insurance usually doesn’t cover termite damage.
- An active infestation can complicate a home sale.
Treatment options and typical costs
Termite Inspection and WDI Report
$75–$250
The inspector checks the foundation, garage, attic and damp spots. Bring up anything you’ve noticed.
- Time
- 60–120 minutes
- Best for
- Every job, real estate closings, and yearly peace of mind
Fumigation for Drywood Termites
$1,200–$4,000 (often $1–$4 per square foot)
Tenting is thorough but leaves no residual protection behind. New drywood swarmers can land on an Ontario home the following season, so follow-up inspections still matter.
- Time
- 2–3 days including tenting and aeration
- Best for
- Widespread drywood termites throughout a structure
Bait Station System with Monitoring
$1,500–$3,500 install, plus $300–$500 per year
Ask how many stations they plan for your Ontario home, how often they'll check them, and what the annual fee covers.
- Time
- 2–4 hours to install; checked quarterly
- Best for
- Colony elimination, wells and slabs, homes near water
Liquid Soil Termiticide Barrier
$1,200–$3,500 (often $3–$16 per linear foot)
A liquid barrier treatment around an Ontario home means trenching and rodding termiticide into the soil along the foundation. Non-repellent products let termites pass through and carry the chemical home to the colony under Ontario.
- Time
- Half a day to a full day
- Best for
- Active subterranean termites; fast knockdown around the foundation
Prices are typical published ranges. Ask what’s included before you compare quotes.
Cardboard boxes stacked on a garage slab are termite food sitting right on their doorstep. Keep storage on shelves.Which termites live around Ontario.
In Ontario's dry heat, desert subterranean termites can build tubes that hang free from ceilings. They'll eat fences, door frames, anything wooden. The termite you're most likely to meet in Ontario is the desert subterranean termite. It nests in soil and builds mud tubes to reach wood. It needs steady moisture. Drywood termites are common around Ontario as well, flying straight into attic framing, eaves and furniture without any soil contact. Look for tiny piles of pellets that look like coarse sand.
Local termites conditions in Ontario.
Knowing Ontario's seasonal timing lets you schedule treatment before the busy stretch rather than after it, which usually means faster service and a more accurate quote. A provider who works Ontario and California every day can point out the specific conditions that matter most here, and getting the scope, price, and follow-up terms in writing makes it easier to compare options. Ontario sits in a semi-arid climate, and that sets the pace for termite activity here: spring swarm season (March-May), warmer earlier in the south. In Ontario, the area is mostly urban, so termites pressure can differ from one block to the next depending on how tight the entry points are and how much food, water, or shelter is close by. An inspection in Ontario usually starts outside and works inward, checking the foundation, gaps around doors and windows, and any moisture or clutter near the structure first.
Sealing the gap where pipes enter the house takes away one of the easiest routes in. It won't replace treatment, but it helps.When termites swarm here.
Swarm season is when termites show themselves. In Ontario, desert subterranean termites usually swarm from July through September, around dusk after monsoon storms. Drywood termites around Ontario tend to swarm in late summer and fall. A swarm outside means a colony is nearby. A swarm inside usually means it's in the house. Save a few in a bag, or snap a clear photo.
Where to look around your house.
Many homes in Ontario sit on concrete slabs, so termites come up through expansion joints, plumbing gaps and settlement cracks. Check the garage edges and behind baseboards. Look where pipes come through the floor. Outside, watch for mud tubes behind shrubs. Keep soil and mulch below the slab edge. The same advice applies across the area, from Ontario out to Rancho Cucamonga and Fontana.
A year of termites in Ontario.
- Summer: with highs around 95°F in Ontario, termites follow moisture, so watch AC drain lines, sprinkler zones and hose bibs. - Fall: with about 15 inches of rain a year in Ontario, make sure gutters and downspouts carry water well away from the foundation. - Winter: a good time to book an inspection in Ontario, before swarm season starts. - Summer: swarm season in Ontario, usually after monsoon storms. Watch porch lights at dusk.
What happens at an inspection.
On a slab, they focus on joints, cracks and pipe gaps. A moisture meter and a probe help them find hidden activity. Afterward, ask them to show you what they found. Photos help. Most inspections take an hour or two. The inspector walks the outside of the house first. They check the foundation, the soil line and nearby wood. Inside, they check the garage, baseboards, plumbing gaps and the attic.
Termites or ants?
- Antennae: termite antennae are straight. Ant antennae bend like an elbow. - Debris: termites leave mud. Carpenter ants leave sawdust. - Tunnels: termite galleries are packed with mud. Ant tunnels are clean and smooth. - Wings: termite wings are all the same length. Ant wings aren’t. - Waist: termites are thick through the middle. Ants are pinched.
Getting ready for treatment day.
Clear a path along the outside walls. Move stored boxes away from garage walls. Mark sprinkler heads and any buried lines. Keep pets and kids inside while the crew works outside. Ask how long to stay off treated soil. Any drill holes in a slab or patio get patched. Soil treatments and bait stations need little prep.
Mulch and termites.
Wood chips right against siding hold moisture termites like. Keep mulch thin and pull it back from the foundation. A dry strip along the house lets you spot mud tubes.
Questions to ask before you sign.
- Is the whole foundation treated, or just one spot? - What does the warranty cover, and for how long? - What does the yearly renewal cost? - What do I need to do before and after treatment? - Which termites did you find, and where? - What product or system will you use?
What affects the price
- Wells, drains, or water features limiting chemical use.
- Amount of drilling through concrete and patios.
- Access to crawl spaces and attics.
- Whole-house fumigation versus spot treatment.
- Species: subterranean, drywood, or Formosan.
- Extent of existing damage needing repair.
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What's your biggest concern about termites?
When to call for help
Termites leave mud. Carpenter ants leave clean tunnels and sawdust. It's also the cheapest termite service. Lenders often ask for one. Get a wood-destroying insect (WDI) report either way. Buying or selling? Hollow-sounding wood is another clue. Call if you see mud tubes, pellets or an indoor swarm.
What you can do yourself
Some of the work is yours. Pull mulch back from the foundation. Fix leaks and clear gutters. Keep firewood away from the house. Treating an active colony is harder. The product has to reach the whole colony. It also needs even coverage around the entire foundation. Store-bought sprays usually kill only the termites you see.
Termites in Ontario
Most houses will see termites at some point. With summer highs around 95°F, Ontario's semi-arid climate decides when local termites are busiest. A typical home in Ontario is worth around $575k, which puts a few hundred dollars for an inspection and prevention in perspective. Ontario only sees about 15 inches of rain a year, so local termites gather wherever water collects, like sprinkler zones, hose bibs and AC drain lines. Termite activity in California is above average.
Local research
Termites in Ontario, CA: what the public record shows
Before you compare quotes, it helps to know which termites actually live in California, when they are busiest around Ontario, and what the state figures look like. Everything below links to the agency or university page it came from.
Termite control products for drywood termites
Drywood and subterranean termite work in California is effectively professional-only; the state licenses it by branch.
UC Statewide IPM ProgramTermite species recorded in California
- Formosan subterranean termite (Coptotermes formosanus) — FDACS lists it in Florida, Alabama, Georgia, Louisiana, Mississippi, South Carolina, North Carolina, Tennessee, Virginia, Texas, Arizona, California and Hawaii. Colonies contain…
- Western drywood termite (Incisitermes minor) — UC IPM: 'California's second most important termite pest', 'commonly found along the Pacific coastal region extending into the Central Valley and deserts of Southern California'…
- Desert subterranean termite (Heterotermes aureus) — UA Extension calls it an 'important structural pest' of the desert Southwest. UC IPM: 'flies in the late afternoon or early evening in July, August, and September'.
- Western subterranean termite (Reticulitermes hesperus) — Oregon State: causes damage to structures in the Pacific Northwest and 'may swarm any time of year'. Utah State describes swarmers 3/8 inch long and workers 1/4–3/8 inch, pale c…
When termites are busiest around Ontario
Reticulitermes swarm in the afternoon in spring or fall on clear days after a soaking rain; drywood swarmers fly in daytime during summer and fall; Heterotermes aureus flies late afternoon/early evening in July–September (UC IPM).
UC IPM: Reticulitermes 'can be encountered in nearly all regions of the state'; the western drywood termite is 'California's second most important termite pest', found along the Pacific coast, Central Valley and Southern California deserts. FDACS lists California among states with Formosan termites. Branch 3 covers 'the control of wood-destroying pests or organisms by the use of insecticides or structural repairs and corrections'; Branch 1 covers fumigation.
Rules that apply in California
Sources: Drywood Termites (Pest Notes); University of Georgia Extension; University of Missouri Extension; Formosan Termite Program; Not All Termites Are Terrible (Home and School IPM Newsletter); Termites | Solve Pest Problems. Figures are quoted as the source prints them. How we check our sources
Simple ways to keep termites away
- Extend downspouts so water drains away from walls.
- Install a vapor barrier over crawl space soil.
- Remove tree stumps and buried wood near the house.
- Keep the termite renewal contract current after treatment.
- Keep gutters clean so water does not pool.
An inspection starts outside, with a flashlight along the foundation line where mud tubes show up first.Did you know?
In Ontario, when danger shows up, soldier termites bang their heads against the tunnel walls to warn the colony.
In Ontario, some tropical termites grow fungus gardens inside the nest and eat the harvest.
Questions people ask
Will termites come back after treatment?
Treatments wear down and new colonies move in. That's what yearly inspections and renewal plans are for. They can.
What is the difference between subterranean and drywood termites?
Drywood termites live inside the wood and leave tiny pellets. Both turn up around Ontario. Subterranean termites live in soil and build mud tubes.
Can I treat termites myself?
The product must reach the whole colony. It also needs even coverage around the foundation. Store-bought sprays usually kill only what you see. Prevention, yes. An active colony is harder.
Can termites damage a house on a concrete slab?
They come up through expansion joints, plumbing gaps and small cracks. Most homes around Ontario sit on slabs, so inspectors check those spots first. Yes.
Is termite treatment safe for kids and pets?
Bait stations are locked and buried. Ask for the label and follow any re-entry times. Used according to the label, yes. Soil treatments stay in the ground.
When is termite swarming season?
In Ontario, termites are best caught early through inspection, because the damage is hidden inside wood until it is far along. In Ontario, a professional inspection looks for mud tubes, damaged wood, and swarming activity, and treatment targets the soil and the colony rather than just the visible wood.
Are termites common in California?
Around Ontario, the usual culprit is the desert subterranean termite.
Nearby cities
Related guides
Sources (10)
The facts in this article come from the public sources listed above. Every home is different, so ask the company you talk to about pricing and what’s included. Published by Termite Exterminator · Updated September 11, 2026 · How we write these guides