The Most Common Roaches You’ll Find in California

Each region of the U.S. has its own unique insects and pests, but cockroaches are found in all 50 states. The types of roaches present in each state are heavily influenced by factors such as climate and housing. For example, hot and humid states like Texas and Florida have high and diverse roach populations. California is also among these states, especially in cities like Los Angeles and San Francisco, which have many multifamily homes.

If you’re wondering which types of roaches are most common in California, we’ve consulted experts to identify the most prevalent species in the Golden State. Read on to learn how to prevent infestations in your home.

Common Roaches Found in California

According to Dr. Tracy Ellis, an entomologist at FarmSense who has worked for the USDA and other government agencies surrounding insect quarantine enforcement and eradication programs, several cockroach species live in California. These include both indoor and outdoor roaches.

“The German cockroach (Blattella germanica) is the most common one found indoors, while the Turkestan cockroach (Blatta lateralis) has quickly become the top outdoor species, even pushing out the once-common Oriental cockroach (Blatta orientalis),” she explains. “The large American cockroach (Periplaneta americana) — about two inches long — is also widespread, especially in cities. Two others, the brownbanded cockroach (Supella longipalpa) and the field cockroach (Blattella vaga), are seen less often but are still present, particularly in Southern California.”

Kyle Turner, Founder, President, and CEO of Pro Active Pest Control, one of the Sacramento and Bay Area region’s fastest-growing pest control companies, echoes a similar sentiment. He notes that the most common roaches he encounters are the German cockroach and the American cockroach.

“German cockroaches are the indoor pest you don’t want — they reproduce rapidly and concentrate in kitchens and bathrooms where moisture and food sources are plentiful,” says Turner. “American cockroaches tend to come from outdoors, entering through drains, gaps around plumbing, and poorly sealed doors; you’ll often find them in basements, garages, and utility areas.”

“In Southern California especially, the Turkestan cockroach has also become prevalent over the past decade, largely displacing the Oriental cockroach in many urban areas,” he adds.

Where Are Roaches Found in California?

As mentioned above, several species of roaches live throughout California. However, some are more common in certain areas than others. For example, as Turner notes, the Turkestan cockroach is rampant in SoCal.

Additionally, as in most regions, roaches prefer warm, dark, and humid environments where food is plentiful.

“These insects thrive in conditions that mirror human habitats — places with readily available food, water, warmth, and shelter,” Ellis adds. “They are especially difficult to control in areas with food crumbs, leaky pipes, warm crevices, cracks, and household clutter.”

How to Prevent Roach Infestations in California

Big cities like Los Angeles and San Francisco tend to experience higher roach populations. This is especially true for multifamily homes or apartment buildings.

“Multifamily housing and apartment dwellings in urban neighborhoods have a higher risk of cockroach infestation than single-family homes,” says Ellis. “Prevention strategies are similar across all structure types and include early-detection monitoring, exclusion by sealing entry points, habitat modification to reduce moist, dark, and cluttered areas, proper sanitation, education on preventing accidental introduction of pests, and regular waste removal. High-risk buildings may also choose to apply gel baits proactively and maintain exterior insecticide barriers around structures.”

Ellis recommends conducting monthly inspections of your space using sticky monitoring traps or shining a flashlight in dark areas. For example, check under sinks, near cracks, behind stoves, and in closets. Roaches love to hide in these small or undisturbed areas. They especially thrive in darkness, so you may never see them unless you actively search for them.

“Inspections also help identify structural breaches around plumbing penetrations, cracks in foundations, gaps along baseboards and door frames, and openings around electrical conduits, indicating where silicone caulk, wire mesh, door sweeps, weather stripping, and other exclusion measures should be applied,” Ellis says.

For a quicker guide to a roach-free home, reference Turner’s “three pillars”: moisture control, exclusion, and sanitation. This might involve fixing leaks, sealing gaps or holes, and cleaning up food spills.

“Roaches are opportunists — they need food, water, and harborage,” he says. “Remove those, and you make your home a very unattractive target.”