Common roaches in California that can become pests: German roach, Oriental roach, American roach, and Vega roach.  Of these species, the one that has the greatest potential for becoming persistent and troublesome is the German roach, which prefers indoor locations. Oriental and American roaches occasionally pose problems in moist, humid areas.

The German roach is a small species of roach. It can be tan through brown to almost black, and has two dark parallel streaks running from the head to the base of the wings. Although it has wings, it is unable to sustain flight. The German roach is one of the most common and prominent household roaches in the world, and can be found throughout many human settlements. These insects are particularly fond of inhabiting restaurants, food processing facilities, hotels, and nursing homes. In colder climates, they are found only near human habitats, since they are not very tolerant to cold. This roach can be seen in the day occasionally, especially if there is a large population or if they have been disturbed. However, sightings are most commonly reported in the evening hours as they are most active at night.

The oriental roach (also known as: waterbug or sewer roach) is a large species of roach. It is dark brown to black in color and has a glossy body. The female Oriental roach has a somewhat different appearance to the male, appearing to be wingless at casual glance but has two very short and useless wings just below its head. It has a wider body than the male. The male has long wings, which cover a majority of its body and are brown in color, and has a more narrow body. The odd male is capable of very short flights, about 2 to 3 meters.

The American roach is the largest species of common roach, and often considered a pest. It is native to the Southern United States, and common in tropical climates. Human activity has extended the insect’s range of habitation. The insect is believed to have originated in Africa, but had become established in the southern U.S. by the time that it was given its name.

The Vega roach (also known: field roach) prefers outdoor locations and is usually found in leaf litter and plant debris.  It is usually found outdoors, but sometimes comes indoors when it is hot or dry and is often mistaken for the German roach. Vega roaches are more olive in color than German roaches and they have a black stripe between the eyes.

Roaches may become pests in homes, schools, restaurants, hospitals, warehouses, offices, and virtually in any structure that has food preparation or storage areas. They contaminate food and eating utensils, destroy fabric and paper products, and impart stains and unpleasant odors to surfaces they contact.

People are repulsed when they find roaches in their homes and kitchens. Roaches may transmit bacteria that cause food poisoning (Salmonella spp. and Shigella spp.). German roaches are believed to be capable of transmitting disease-causing organisms such as Staphylococcus spp., Streptococcus spp., hepatitis virus, and coliform bacteria. They also have been implicated in the spread of typhoid and dysentery. Indoor infestations of roaches are an important source of allergens and risk for asthma among some populations. The levels of roaches and allergens are directly related to roach density, housing disrepair, and sanitary conditions.

Roaches are nocturnal. They hide in dark, warm areas, especially narrow spaces where surfaces touch them on both sides.  Immature roaches tend to stay in even smaller cracks where they are well protected. Roaches tend to congregate in corners and generally travel along the edges of walls or other surfaces.