How Cockroaches Get Into Missouri Homes

Understanding how cockroaches enter homes is the first step in preventing infestations — and in understanding why some homes are repeatedly troubled by cockroaches while neighboring homes are not. Entry methods differ significantly between species, which reinforces the importance of identifying what you are dealing with before treating.

Passive Introduction (German Cockroaches)

German cockroaches are almost exclusively introduced rather than invading on their own. They do not come in from the yard or migrate from neighboring fields. They arrive via:

Grocery Bags and Cardboard Boxes

Egg cases (oothecae) and nymphs easily hide in the corrugations of cardboard boxes. Grocery bags — particularly the reusable kind used repeatedly in stores — can carry eggs or nymphs. This is the most common introduction route for German cockroaches into previously clean homes: a single egg case in a grocery bag or a case of canned goods containing a hitchhiking roach is enough to start an infestation.

Used Appliances

Used refrigerators, microwaves, toaster ovens, coffee makers, and other kitchen appliances are a significant source of German cockroach introduction. The warmth of motors and electronics makes appliances ideal harborage. A used appliance from an infested home can harbor egg cases that hatch weeks after the appliance is in your home.

Furniture and Personal Belongings

Moving from an infested home or apartment, receiving furniture or boxes from an infested location, or having guests who come from an infested environment can all introduce German cockroaches into a new location.

Multi-Unit Buildings

In apartments and condominiums, German cockroaches travel through shared wall voids, plumbing chases, and gaps around pipes to move between units. An infestation in one unit in a building makes all adjacent units vulnerable regardless of how clean they are maintained.

Active Entry (American and Oriental Cockroaches)

American and Oriental cockroaches can maintain outdoor or sewer-based populations and actively enter structures:

Floor Drains and Sewer Connections

Floor drains in basements, laundry rooms, and garages connected to the sewer system are a primary entry point for both American and Oriental cockroaches. Infrequently used drains where the water trap has dried out provide direct access from the sewer. Running water down the drain periodically maintains the trap seal.

Utility Penetrations

Gaps around water pipes, gas lines, electrical conduit, and other utility penetrations through foundation walls and floors provide entry from below and from outside. American cockroaches in particular use these routes to enter from crawlspaces and the exterior soil.

Gaps in Foundation and Around Doors

Cracks in the foundation, gaps under exterior doors without proper sweeps, and gaps around basement windows are entry points for larger roach species that forage from outside. Oriental cockroaches in particular move in from crawlspaces and exterior areas at ground level.

Crawlspace Vents

Damaged or missing crawlspace vent screens allow cockroaches to enter the crawlspace, from which they can access the living areas of the home through floor penetrations and wall voids.

Prevention Steps

• Inspect grocery bags and cardboard boxes before bringing them inside — check the folds and bottom of boxes
• Thoroughly inspect used appliances before purchase and again before installation
• Seal gaps around all utility penetrations through foundation and floor
• Install or maintain floor drain covers on infrequently used drains; run water regularly to maintain trap seals
• Install door sweeps on basement and exterior doors
• Repair damaged crawlspace vent screens
• In multi-unit buildings, report suspected activity promptly so building management can address shared entry points