Cockroaches are common household pests that may spread bacteria, contaminate food and surfaces, damage property, and cause allergic reactions.

Most indoor cockroach infestations are caused by German cockroaches. They prefer warm, humid locations that are close to food and water, such as kitchens and bathrooms. Other cockroach species may occasionally be seen indoors, but are primarily found outdoors. These include the oriental cockroach, smokybrown cockroach, American cockroach, and Turkestan cockroach.

Cockroaches need only small amounts of food and water, so they can survive even in tidy homes. All food should be stored in insect-proof containers, and garbage should be stored in containers with tight-fitting lids. Remove clutter that could provide harborage for cockroaches. You will also need to seal up cracks and crevices where crumbs and food residue can collect, and where cockroaches can hide.

If you continue to see cockroaches after these steps, an insecticide may be warranted. Look for insecticide baits that are labeled for cockroaches. As with any pesticide, you MUST read and follow the label.

Sanitation and household insecticides are enough to resolve most problems with cockroaches, but if you have a severe infestation, you will need to contact a pest control service.

The District does NOT conduct residential or commercial pest control, but can identify suspected cockroach specimens and provide recommendations for control. If you’d like to schedule a technician visit, call 650-344-8592 or make a service request online.

For more information about cockroaches, visit the UC IPM webpage.

 

A few common cockroaches in San Mateo County...

Indoor Cockroaches

German cockroach (Blattella germanica): These are small, pale brown insects with two dark stripes on the thorax. Although adults have wings, they cannot fly. The geographical origin of the German cockroach is contested, as the long-held assumption that it is native to Europe has been challenged by recent evidence suggesting it may have originated in Africa, South Asia, or Southeast Asia. German cockroaches are the species of cockroaches most likely to infest homes and buildings in California. They prefer humid areas such as kitchens and bathrooms.

American cockroach (Periplaneta americana): These are large reddish-brown insect with pale bands on the thorax. Adults of both sexes have wings and can fly. Despite its name, this species originated from tropical areas of Africa. American cockroaches usually live outdoors or in underground areas such as sewers or storm drains, but they can also infest structures.

 

Outdoor Cockroaches

Oriental cockroach (Blatella orientalis): These glossy dark brown to black insects are also called water bugs by some people. Although males have wings, these cockroaches cannot fly and are unable to climb smooth vertical surfaces. They are sometimes found trapped in sinks. Despite its name, this species is native to areas around the Caspian and Black Seas, which lie at the border between Asia and Eastern Europe. These cockroaches prefer dark, cool, and damp, usually outdoor habitats with decaying organic matter like leaf litter, and water meter boxes.

Turkestan cockroach (Blatta lateralis): Females of this species look very similar to oriental cockroaches; they are shiny and dark brown with cream-colored markings at the edge of wing buds. Males more closely resemble a smaller, lighter-colored version of an American cockroach; they are yellow/tan, winged, with cream-colored stripes on the edges, and can fly. Nymphs are red and brown, and give the insect one of its common names: red runner. Turkestan cockroaches originated from arid regions of Africa and the Middle East, and were likely introduced to the U.S. in the 1970s. They are also commonly sold as feeder insects for pet reptiles. Turkestan cockroaches are slowly displacing the oriental cockroach in many parts of the Southeast United States. They are often found in water meter boxes and other somewhat enclosed, humid sites.

Three-Lined cockroach (Luridiblatta trivittata): This is the smallest cockroach in California, with three dark stripes running down the length of the back. Neither male nor female has wings, and it cannot fly. This cockroach originated from the Mediterranean region of Europe and North Africa. They were introduced to the United States in the early 2000s and have become a common garden insect in the San Francisco Bay Area.

 

 

Page last reviewed: June 8, 2026