Central California
Pest Season Calendar
Which pests are active each month in Monterey, San Benito, Santa Cruz, and Santa Clara counties — and what to do about them.
Based on 20+ years of service calls across four counties.
At a Glance
Monthly Activity Quick Reference
Activity levels for the eight most common pests in our four-county service area. Peak = highest activity / swarm season. Active = significant pressure. Low = present but reduced.
| Month | Sub. Termites | Drywood Termites | Argentine Ants | Rodents | Gophers | Wasps / YJ | Fleas | Bed Bugs |
|---|---|---|---|---|---|---|---|---|
| January | Low | — | Low | Active | Active | — | — | Low |
| February | Active | — | Low | Active | Active | — | — | Low |
| March | Peak | — | Peak | Active | Peak | — | Active | Low |
| April | Peak | — | Peak | Active | Peak | — | Active | Active |
| May | Active | Low | Active | Low | Active | Low | Active | Active |
| June | Active | Active | Active | Low | Active | Active | Peak | Active |
| July | Active | Peak | Active | Low | Active | Peak | Peak | Peak |
| August | Low | Peak | Active | Low | Active | Peak | Peak | Peak |
| September | Low | Active | Active | Active | Active | Peak | Active | Active |
| October | Low | Low | Active | Peak | Active | Active | Active | Active |
| November | Low | — | Active | Peak | Active | Low | Low | Active |
| December | Low | — | Low | Peak | Active | — | Low | Low |
Month by Month
What to Expect — and What to Do
January
What’s Active
- Rodents: Mice and rats have been indoors since November, now well-established in wall voids and attic insulation — seeking warmth and nesting material.
- Gophers: Pocket gophers are active year-round in Salinas Valley; winter rains soften soil, making tunneling easy in residential lawns and gardens.
- Subterranean Termites (low): Activity is reduced in cold weeks but coastal Monterey soil rarely freezes — colonies remain active and will surge with any warm spell.
What to Do This Month
- 1.Inspect garage doors, crawl space vents, and utility penetrations for rodent entry points.
- 2.Walk your lawn for fresh gopher mounds after rain — fresh soil is the key indicator.
February
What’s Active
- Rodents: Rodent pressure remains high. Females are beginning to breed indoors — populations can double quickly if entry points remain unsealed.
- Subterranean Termites: As soil temperatures begin rising along the coast, Reticulitermes hesperus colonies start building pressure. Late February warm spells can trigger early swarming.
- Ants (scouts): Argentine ant scouts emerge after the first heavy rain, probing foundations for food and moisture. Most homeowners don't see the invasion until March.
What to Do This Month
- 1.Schedule a rodent exclusion inspection before spring breeding accelerates populations.
- 2.Check window sills and door frames for mud tubes — early termite sign.
March
What’s Active
- Subterranean Termites (Peak swarm season): Reticulitermes hesperus swarms on warm, humid days after rain when soil temperatures exceed 70°F. Look for winged termites (alates) near windows and light fixtures.
- Argentine Ants (Peak): Spring rain triggers supercolony expansion. A single Argentine ant supercolony can stretch across multiple city blocks — this is when infestations escalate rapidly.
- Gophers (Peak): Breeding season peaks in March; females produce 1–3 litters per year. Mound activity doubles in many Salinas Valley properties.
What to Do This Month
- 1.If you see winged insects emerging from the soil or walls, collect a sample and call immediately — this is the single most time-sensitive pest event of the year.
- 2.Treat ant trails at the foundation before scouts recruit the full colony indoors.
April
What’s Active
- Subterranean Termites (Peak swarm continues): Swarm season extends through April in inland areas. Hollister and Gilroy see peak swarm events 2–3 weeks after the coast.
- Argentine Ants (Peak): Colony expansion is at maximum. Ant trails are now visible inside kitchens, bathrooms, and along exterior walls. Treatment before May prevents summer infestations.
- Fleas (beginning — inland): Warmer inland areas like Hollister and Morgan Hill see flea season start in April when daytime temperatures hold above 65°F. Outdoor pets are the primary vector.
What to Do This Month
- 1.Schedule a WDO (Wood Destroying Organism) inspection if you're buying or selling a home — this is peak season and inspectors book out fast.
- 2.Treat pets and outdoor areas for fleas before populations establish.
May
What’s Active
- Drywood Termites (Low — beginning): Incisitermes minor begins its swarming period in coastal areas. Early signs: small piles of pellet-like frass near windowsills or door frames.
- Wasps (Queen establishment): Wasp queens that overwintered emerge and begin building new nests. Nests found in May are small (golf ball size) and easy to treat before colonies grow.
- Fleas: Flea populations establish across all service counties. Properties with dogs and outdoor cats require treatment of both the animal and the yard.
What to Do This Month
- 1.Locate and treat wasp nests while they are small — a May nest has 10–20 workers; a July nest has 200–400.
- 2.Inspect roof eaves, attic vents, and wooden trim for early signs of drywood termite frass.
June
What’s Active
- Drywood Termites (Active): Swarming events intensify along the coast. Coastal fog and warm afternoons create ideal conditions for Incisitermes minor.
- Fleas (Peak): June marks the start of peak flea season. Larvae in carpet and yard soil reach adulthood in warm conditions — infestations grow exponentially.
- Yellow Jackets (Active): Yellow jacket colonies double in size through June. Nests under eaves, in wall voids, and in ground burrows are increasingly aggressive when approached.
What to Do This Month
- 1.Treat flea infestations now — July and August are worse. A full treatment includes pets, interior carpets, and the outdoor yard.
- 2.Do not attempt to remove a June yellow jacket nest without protective equipment — colonies are now large enough to be dangerous.
July
What’s Active
- Drywood Termites (Peak swarm): Peak swarming for Incisitermes minor — the most common drywood species in California. Swarms occur on warm afternoons, often after the first hot inland day. Look for discarded wings in windowsills.
- Yellow Jackets (Peak): Yellow jacket colonies reach maximum population in July — some ground nests contain 3,000–5,000 workers. This is the most dangerous month for stings. Avoid sweet drinks outdoors.
- Bed Bugs (Peak): Summer travel season is peak bed bug transmission. Hotels, rental cars, and vacation accommodations are common vectors. Inspect luggage and mattress seams after any trip.
What to Do This Month
- 1.If you see swarms of winged insects from wood structures, call immediately — drywood termite swarms mean an active colony is already established inside the wood.
- 2.Inspect for bed bugs after travel: check mattress seams, headboards, and luggage before bringing items inside.
August
What’s Active
- Drywood Termites (Peak continues): August swarms can be confused with flying ants. Key difference: termite alates have equal-length wings and a thick waist. Flying ants have a pinched waist and unequal wings.
- Yellow Jackets (Peak — most aggressive): Late summer yellow jackets are at peak aggression as colonies begin to stress. Natural food sources decline, making them bolder around human food and garbage.
- Fleas (Peak): Flea populations peak in August. Hot dry conditions concentrate larvae in shaded soil areas (under decks, dense shrubs) where they survive the heat.
What to Do This Month
- 1.Schedule a fumigation before fall if drywood termites were spotted this summer — October and November are ideal fumigation months (lower weather disruption).
- 2.Keep garbage cans sealed and avoid leaving sugary drinks outdoors — yellow jackets are aggressive scavengers this month.
September
What’s Active
- Rodents (increasing): This is the most critical month for rodent exclusion. As nighttime temperatures drop, mice and rats begin actively seeking indoor harborage. Once established, populations are much harder to remove.
- Yellow Jackets (Peak aggression): September yellow jackets are at their most aggressive as colonies begin to collapse. Worker foraging is frantic — this is the month most stinging incidents occur.
- Gophers (agricultural displacement): Fall harvests in the Salinas Valley displace large gopher populations from agricultural fields into adjacent residential properties.
What to Do This Month
- 1.Walk the perimeter of your home and seal any gap larger than a quarter inch — this is the single highest-ROI pest prevention action of the year.
- 2.Wait until mid-October for yellow jacket nests: workers die off naturally, making removal far safer and easier.
October
What’s Active
- Rodents (Peak): Rodent pressure is at its annual peak in October. Mice can enter through a gap the size of a dime; rats through a quarter-size opening. Wall voids, attics, and crawl spaces are primary targets.
- Argentine Ants (Active): Coastal areas see continued ant activity through October. Colonies move deeper as temperatures drop, concentrating near warm interior walls.
- Yellow Jackets (Dying off): Yellow jacket colonies collapse by late October. Dead workers in odd places (floors, counters) are normal — they are disoriented as the colony fails.
What to Do This Month
- 1.Set monitoring stations in the garage, crawl space, and attic if you have not already completed exclusion work.
- 2.Schedule fumigation for any confirmed drywood termite infestations before winter — this is the last comfortable fumigation window.
November
What’s Active
- Rodents (Peak): Mice and rats are fully established indoors by November. Scratching sounds in walls and ceilings at night, chewed food packaging, and droppings are the key signs.
- Argentine Ants (Coastal): Coastal Monterey and Santa Cruz areas see ant activity through November due to mild temperatures. Inland areas see a natural slowdown.
What to Do This Month
- 1.If you hear scratching at night, act quickly — a single pregnant mouse becomes a colony of 20–30 within 6 weeks.
- 2.Clear brush, firewood stacks, and debris from the home foundation — these are rodent harborage points that make exclusion ineffective.
December
What’s Active
- Rodents (Peak — established): Rodent populations that moved in during fall are now breeding indoors. Roof rats are particularly active in coastal areas with mature trees providing roof access.
- Gophers (Active): Pocket gophers do not hibernate and remain active year-round in Salinas Valley clay soils. Winter mounds are often more visible after rains clear the surface.
What to Do This Month
- 1.Complete rodent exclusion repairs before the holiday rush — gaps created by seasonal décor installation (outdoor lights, attic access) are common entry points.
- 2.Plan your spring termite inspection for February or March — schedule early, slots fill during swarm season.
Common Questions
Pest Season FAQ
When do termites swarm in Monterey County?
Subterranean termites (Reticulitermes hesperus) swarm primarily in March and April along the Monterey coast, triggered by warm temperatures after rain when soil temperature exceeds 70°F. Drywood termites (Incisitermes minor) swarm later — July through September — typically on warm afternoons following the first hot inland days of summer. If you see winged insects emerging from wood structures or soil, call for an inspection immediately.
Why do ants invade every spring in California?
Argentine ants form massive supercolonies that can stretch across several city blocks. Rain disrupts their outdoor nesting areas and triggers colony expansion, which is why ant invasions seem to appear overnight after the first heavy spring rain. The ants you see indoors are scouts looking for food and moisture on behalf of a colony that may contain millions of workers. Treatment must address the colony — not just the visible trail.
When should I schedule a rodent inspection?
The best time to schedule a rodent inspection is September — before rodents move indoors for winter. If you schedule exclusion work in September, you block entry before populations establish. By November, rodents are already breeding inside wall voids and attic insulation, making treatment significantly more involved. If you hear scratching sounds at night or find droppings, schedule immediately regardless of season.
Are there year-round pests in Central California?
Yes. Pocket gophers are active year-round in Salinas Valley. Argentine ants remain active in coastal areas throughout the year due to mild temperatures. Rodents — especially roof rats — are present indoors year-round once established. Bed bugs have no seasonal pattern and can be introduced any time through travel or secondhand furniture. The mild Central California climate means there is no true "off season" for pest pressure.
How does the Salinas Valley's agricultural setting affect pest seasons?
The Salinas Valley's year-round agriculture creates unique pest dynamics. Harvest cycles displace large gopher and ground squirrel populations from fields into adjacent residential neighborhoods — typically in September and October. Agricultural operations also support large rodent populations that expand into residential areas during crop rotations. Properties within a mile of active farmland typically experience higher pest pressure than urban properties, and timing treatment to coincide with nearby harvest schedules is often effective.
Don’t Wait for Peak Season
Schedule a Free Inspection Now
Early treatment is always more effective — and less expensive — than treating an established infestation. Most inspections are scheduled within 1–3 business days.