American Cockroaches. How to Identify Them and Keep Them Out

Adults are about 1.3 to 2.1 inches long, among the largest cockroach pests in homes. They are flat and oval with spiny legs and long antennae.² The wings are glossy reddish brown to dark brown. The shield behind the head is reddish brown with a yellowish brown border.²

They have wings but seldom fly when disturbed.² Nymphs look like adults without wings.² Egg cases are mahogany to blackish brown and about 3/8 inch.²

Oriental roaches are the lookalike. They are about 1.25 inches, nearly black, with short wing stubs.¹ Smokybrown roaches are about 1.5 inches and dark brown to mahogany, but they are now rarely seen in California.¹

Compare them with the small German cockroach, or go back to the cockroach guide.

A female makes 6 to 14 egg cases in her life. She carries each for a few hours or days, then drops or glues it in a sheltered crack near food. Eggs hatch in 38 to 49 days, averaging 44.²

Early nymphs molt about monthly. Older nymphs molt every 1 to 6 months. There are 10 to 13 nymph stages.² Egg to adult averages about 15 months, with a range of 9.5 to 20. Adults can live more than a year and keep breeding when conditions are good.²

Each egg case holds about 12 young, and one female and her offspring can produce over 800 roaches in a year.¹

You will see them before you see their droppings, since they are big. They hide by day and come out at night to look for food and water.²

• Large reddish brown roaches near drains, basements and boiler rooms.²
• Egg cases in cracks near food, about 3/8 inch and mahogany brown.²
• Cast skins and fecal specks.¹
• A strong, unpleasant odor on food or in hiding spots.²

In warm weather, check outside 1 to 2 hours after sunset. Look for roaches coming out of cracks.² Note where they come from so you can treat those spots.

American roaches can spread Salmonella and Shigella, which cause food poisoning.¹ Ohio State says they can harbor bacterial and viral pathogens in their feces or on their bodies. They can contaminate food and prep surfaces with organisms that cause food poisoning, dysentery or diarrhea.²

They also foul food products and leave a strong odor behind.² Indoor roach allergens are linked to asthma risk in children, especially in multi unit housing.¹

Treat any roach seen in food areas as a cleanup job first, then a pest job.

Work from the outside in. Ohio State says an indoor problem in warm weather should always trigger an outdoor check, since roaches may be in the sewer system, landscape or building.²

Seal the entry points. Add door sweeps, thresholds and weatherproof seals. Screen windows and attic vents, and caulk cracks and utility openings.² Move firewood, lumber and trash cans away from the building, avoid thick mulch and keep gutters clean.²

Then bait. Baits in liquid, paste, gel or granule form work indoors and outdoors, but roaches must prefer the bait to other food, so sanitation matters.² Liquid residual insecticides go around the foundation and entry points. Seal the cracks afterward.²

Some products are labeled for licensed, certified applicators only, and the label rules always apply.²

One time treatment runs $100 to $600 for most homes, with a national average near $275.³ American roaches usually cost less than German roaches because they are easier to eliminate.³

Severe infestations run $400 to $600 and typically need 3 to 4 visits.³ Quarterly prevention plans run $100 to $175 per visit.³

Large homes and layouts with many bait spots cost more.³ If roaches come from outdoors, ask the company to treat the foundation and entry points too, and to say how it will seal them.

• Install door sweeps, thresholds and weatherproof seals on exterior doors.²
• Screen windows and attic vents.²
• Caulk cracks and holes on the building exterior, and around plumbing, cable and utility lines.²
• Move firewood, lumber and trash cans away from the building.²
• Avoid thick mulch, mow weedy growth and prune branches off the building.²
• Ventilate basements and crawl spaces, and keep them clear of clutter.²
• Keep gutters clean.²
• Store food, fix leaks and take out garbage often.²

Seal first, then treat. Sealing after treatment locks in the result.²

They like warmth, above 82°F.¹ In summer they can move from one building to the next, through cracks in foundations, loose doors and windows, and along pipes.²

Outdoors they pile up in moist, shaded leaf litter, rotting stumps, planters, roof overhangs and gutters.² Indoors they favor basements, boiler rooms, steam tunnels and areas around pipes and drains.²

Plan your outdoor cleanup and sealing before summer, and re-check after sunset when it is warm.²

Inspect the outside of the building 1 to 2 hours after sunset. That is when these roaches start looking for food.²

This guide builds on an Ohio State University Extension fact sheet. It calls the American cockroach the most common roach in city sewer systems and says it favors high humidity.² People sometimes call it a waterbug or palmettobug.²

In Ohio, a company that applies pesticides for hire needs a commercial applicator license and a business license.⁴ Applicators pass a core exam and at least one category exam, and the passing score is 70 percent.⁴ Licenses expire each Sept. 30.⁴

Ask to see the license, and ask who will seal the entry points. Go back to the cockroach guide for more.

The American roach is one of five species commonly considered pests in California.¹ It prefers temperatures above 82°F and can live outdoors in sewers and drains.¹

Oriental roaches are being displaced by Turkestan roaches in southern California and the Central Valley.¹ Know which species you have before you buy bait.

Structural pest control, which covers household pests and pesticide use, is regulated by the Structural Pest Control Board.⁵ Verify the company on the Board's license lookup before work starts.⁵

Egg cases of the American roach are about 3/8 inch and incubate about two months.¹ Each holds about 12 young.¹