Cockroaches are among the most disagreeable insects that must be dealt with by occupants of homes, apartments, or commercial establishments. In addition to their repulsive and annoying characteristics, they eat or contaminate human food and leave a persistent, objectionable odor in infested areas. Foraging or feeding cockroaches also spread human disease by depositing disease organisms on food, dishes, or other items.

Cockroaches grow and mature by gradual metamorphosis. There are three stages in the life cycle: egg, nymph, and adult. Generations overlap, so all stages may be found at any time of year.

Females deposit eggs in bean-shaped or purse-like leathery egg cases called oothecae. These are dropped or attached to out-of-the-way places by the females shortly after their formation. Egg cases of the various species are quite distinctive and may be used as an aid in determining what species are involved in an infestation (Fig. l).

The nymphs which hatch from the eggs resemble the adults, except that they are smaller, have undeveloped wings, and frequently are a somewhat different color. Nymphs develop rather slowly, growing by progressive stages, each stage terminated by molting of the skin which permits the insect to increase in size. Nymphs may molt 5-13 times before transforming into adults, the number depends upon the species and local conditions.

Cockroaches typically are nocturnal insects; they only appear during the day when disturbed or when there is an excessively large infestation. Cracks and crevices are favored hiding and breeding areas.

In the Pacific Northwest, four cockroach species may be encountered in homes, apartment complexes, or commercial establishments. They differ enough that the control techniques used against one species may not necessarily be effective against another. Because various combinations of these cockroaches may occur in a building at the same time, it is essential to accurately identify the species present before control is begun.

German Cockroach, Blattella germanica

The German cockroach is the most common cockroach in the Pacific Northwest; it is found in homes, apartments, restaurants, hospitals, or other buildings where food is stored, prepared, or served. The adult is ^l/₂ inch long, pale brown, and has two dark brown lengthwise stripes on the shield behind the head. Adults are winged but rarely fly. Under ideal conditions, they may live up to 12 months.

The slender egg case is ¹/₃ inch long and light tan. The female carries it at the tip of her abdomen until the eggs are nearly ready to hatch (Fig. 2). The case is then dropped in a secluded location and the nymphs emerge one to two days later. A female may produce four to eight egg cases during her lifetime, each containing 30-48 eggs.

German cockroach nymphs are darker than adults. The most characteristic marking is a single pale brown stripe separating two dark brown stripes running about halfway down the middle of the upper abdomen. The nymphal stage is completed in 1¹/₂-4 months.

The German cockroach produces more eggs and has more generations per year (three to four) than other cockroaches; thus, a troublesome infestation can develop rapidly after the chance introduction of a few individuals. These cockroaches are often accidentally brought into buildings with groceries (especially bagged potatoes and onions), beverage cartons and cases, used furniture and appliances, and dry cleaning. Adults may also migrate from nearby infested dwellings. German cockroaches normally inhabit the kitchen but are also likely to occur in the bathroom, particularly if the kitchen and bathroom share a common wall. During the day, adults and nymphs may be found hiding clustered together under, around, or even in the walls of appliances such as stoves, refrigerators, and dishwashers; around sinks, especially in the dead space between the sink and wall; beneath or around the water heater; under, inside, or in cracks around cabinets, closets, and pantries; and behind baseboard molding.

American Cockroach, Periplaneta americana

The American cockroach is the largest cockroach found in dwellings. The adult is 1¹/₂ inches long, reddish-brown to brown, and has a light yellow or tan band around the edge of the shield behind the head. Both sexes have well-developed wings and can fly. The wings of the male extend slightly beyond the tip of the abdomen (Fig. 3) while those of the female do not. Adults may live up to 15 months.

The egg case is dark brown and approximately ¹/₃ inch long. The female deposits the egg case in sheltered areas on or near the floor, usually close to a food source. She frequently conceals the case with debris which she attaches to its surfaces Egg cases are formed at the rate of about one per week until 15-90 have been produced. Each contains 16 eggs.

Young nymphs are grayish-brown with each progressive molt becoming more reddish brown. The time required to complete the nymphal stage varies from 5-15 months.

The American cockroach is most commonly found in restaurants, supermarkets, and other commercial buildings where food is prepared or stored, but it also may invade apartments or homes from sewer systems via the plumbing. Within a household, this cockroach prefers to live in cluttered basements, feeding upon stored paper goods and seepage from around sewage pipes. When an infestation increases in size, individuals may spread to the kitchen, bathroom, or other rooms.

Brownbanded Cockroach, Supella longipalpa

The brownbanded cockroach adult is ¹/₂-⁵/₈ inch long. The female's wings are a uniform reddish-brown to dark brown, while those of the male are dark brown at the base, becoming increasingly lighter toward the tips. Both sexes have a light yellow or pale brown band that runs across the base of the wings and another broken band a third of the distance from the base. The male's wings cover the abdomen completely; the female's wings are short and never cover all of the abdomen (Fig. 4). The female's abdomen is much broader and more rounded then the male's. These cockroaches are very active and the adults jump when disturbed; only males can fly. Adults may live from three to eleven months.

The egg cases are a light reddish-brown, ¹/₄ inch long, and are usually attached in clusters to furniture, draperies, wall decorations, shelving, and ceilings. Each case contains 16 eggs and a female may produce 10-20 cases in her lifetime.

The nymphs are readily identified by two yellow bands that cross the upper abdomen. The developmental period of the nymphs ranges from three to six months

Brownbanded cockroaches are more apt to be found in private residences than in commercial buildings. Adults and immatures prefer to hide in warm, elevated areas near the ceiling, behind wall decorations and loose wallpaper, in closets, beneath or inside upholstered furniture, and in electrical appliances such as television sets, stereos, and toasters. These cockroaches may infest any room in a dwelling. As a result they are often more difficult to control than other cockroach species.

Oriental Cockroach, Blatta orientalis

The adult oriental cockroach is uniformly glossy dark brown to black. The female is 1¹/₄ inches long, with a broad abdomen and stubby wings (Fig. 5). The male is 1 inch long, slender, and has wings which cover two-thirds of the upper abdomen. Neither sex will fly nor even run very quickly when disturbed. Adult longevity ranges from one to six months.

Egg cases are dark reddish-brown, ¹/₂ inch long, and appear to be slightly inflated. The female deposits the case in a sheltered location near a food supply. Anywhere from 8-15 egg cases are produced per female, with each case containing 16 eggs.

Immature oriental cockroaches are the same color as the adults and the nymphal stage requires about one year for completion.

The oriental cockroach feeds on a wide range of decaying organic matter and has the reputation of being the filthiest of the household infesting species. Outdoors, these insects are found in cool, moist habitats such as beneath decomposing leaves or stones, flower and garden mulching materials, in trash and garbage piles, and in municipal sewer systems. Occasionally, during unseasonably cool periods or with the onset of fall weather, there may be a mass movement of oriental cockroaches into buildings. These cockroaches invade man-made structures through sewer drain pipes, foundation cracks, ventilators and poor-fitting doors. Normally this species does not become abundant in buildings. Nevertheless, populations can become very large at times, especially in moist areas such as basements, near drains or leaky water pipes, and beneath refrigerators, sinks, and washing machines .

Prevention and Sanitation

Prevention is the key to successful cockroach control Preventive measures will minimize cockroach invasion of buildings and eliminate or greatly reduce availability of food, water, and shelter. It is much easier and usually less costly to keep cockroaches on the outside than it is to get rid of them once inside.

These insects can be discouraged from entering buildings by sealing any cracks of ¹/₈ inch or more in foundations and exterior walls. The seal around air conditioners, doors, windows, and other structural openings should be examined to insure that there are no gaps which permit cockroach entry. Refuse should be stored in durable, securely covered containers and not kept next to a building. Incoming merchandise such as beverage cartons, groceries, dry cleaning, luggage, and used appliances or furniture should be inspected for hitchhiking cockroaches and/or their egg cases.

Inside a dwelling, all cockroach hiding areas and food sources should be eliminated. Cracks and holes in floors, walls, and ceilings should be repaired and openings around plumbing fixtures, furnace flues, electrical outlets, between window sills and walls, and along baseboards or ceiling moldings should be sealed. Leaky water faucets and pipes should be repaired.

Sanitation or cleanup will aid considerably in cockroach control. Unwashed dishes, kitchen utensils, and exposed food products should not be left overnight. All spilled liquids should be cleaned up. Areas beneath cabinets, furniture, sinks, stoves, and refrigerators should be cleaned often, as should cupboards, pantry shelves, and storage bins where tiny particles of food frequently accumulate. Kitchen wastes and dry pet food should be kept in cockroach-proof containers. If pets are fed indoors, leftover food should not be allowed to remain in the feeding dish overnight. Accumulations of stored papers, boxes, or other nonessential items should be disposed of, since these items provide excellent hiding and breeding sites for cockroaches.

Insecticides

Cockroach infestations can be reduced by either non-residual or residual insecticides. Nonresidual insecticides kill cockroaches by direct contact with the insecticide during the application; residual insecticides leave deposits on treated surfaces which kill cockroaches for variable periods of time after the application. One treatment rarely results in total control; retreatments are usually necessary. Frequency of treatment will depend upon sanitation practices, thoroughness of insecticide application, and how vulnerable the structure is to reinfestation.

The type of insecticide and the application method used will depend on the location and nature of the infestation. No one insecticide is best, but various combinations can be effective. Regardless of the insecticide selected, a chemical applied to areas where cockroaches hide during the day or regularly travel at night will kill more individuals than a chemical applied to areas which cockroaches seldom frequent. Favored hiding areas of each species have been described previously.

Residual sprays. Oil-base or water-emulsion sprays are applied as spot or crack and crevice treatments. These insecticides are available in pressurized containers, in non-pressurized containers with built-in spray pumps, and as concentrates to mix with water before applying with a compressed-air sprayer, plunger-type sprayer, or even a paint brush. When applied, the spray should wet or dampen the treated surface but not to the point of puddling or running. Oil-base insecticides should be used with care; they may dull, stain, or injure asphalt tile, linoleum, painted surfaces, plaster, certain plastics, houseplants, and rubber backing on carpet. They may also create a fire hazard when used near an open flame like the pilot light on a gas stove, furnace, or water heater In these situations, water-emulsion sprays should be used. Precautions should also be taken with water-emulsion sprays as they may stain light-colored carpeting, draperies, wallpaper, and other water-soluble materials, or even short out electrical circuits. Water emulsions also don't adhere as well as oil-base sprays to smooth materials such as glass and metal.

Non-residual sprays. Non-residual sprays are most useful for finding the location and size of cockroach infestations. These sprays are sold in ready-to-use pressurized containers (aerosol bombs) . A non-residual spray by itself will not provide adequate control, but when used with a residual insecticide a high degree of control can usually be achieved. A small amount of spray squirted into harborage areas forces rapid movement of cockroaches onto surfaces previously treated with the residual material.

Dusts. Cockroaches can also be controlled with insecticidal dusts. Dusts are useful because they may be placed deep into cracks and crevices, wall voids under large appliances and furniture, around electrical outlets and wiring, on very smooth or porous surfaces, and in other areas where spray applications might be impractical or unsafe. Dusts generally provide longer residual control than sprays but become ineffective in wet locations. Dusts are purchased in ready-to-use form and are applied with a plastic squeeze bottle, rubber bulb, or bellows-type hand duster. When properly used, dusts should leave a barely visible, uniform deposit on the treated surface.

Sometimes a combination of dust and spray treatments is more effective than either alone. When used with sprays, dusts should be applied after the spray has dried.

Traps

Trapping is an effective way to reduce cockroach populations, especially when used along with preventive and insecticidal measures. Trapping also can determine harborage areas and infestation severity, monitor effectiveness of chemical controls, and detect population increases which may require insecticide treatment. Several types of traps can be purchased. Most are about the size of a large matchbox, have openings at both ends, and have the inside surface covered with a very sticky adhesive and slow-release food attractant (Fig. 6a). Cockroaches detect the food odor, enter the trap, and become immobilized by the adhesive.

Traps should be positioned (with both ends unobstructed) to intercept cockroaches as they travel to and from hiding and feeding areas. If no cockroaches are caught in a trap after two nights, change its location. A properly placed trap can catch numerous cockroach adults and/or nymphs daily (Fig. 6b). Traps are particularly effective against brownbanded and German cockroaches. The number of traps required for a building will vary with the kind of cockroach present and the severity and location of the infestation. Traps are inexpensive, convenient to use, disposable, and contain no toxic insecticide.

Professional Control

If a severe or widespread cockroach infestation occurs, or if you are in doubt as to proper control measures, employ a reputable pest exterminator. These professionals have the materials and training to do a thorough job.

All insecticides are poisonous. They always must be handled carefully to minimize the possibility of harm to humans and animals by direct contact or through contamination of food and water. The key to safety is a knowledge of the hazards involved in handling and applying insecticides.

1. Read the product label; understand the directions and precautions before preparing and/or applying. Use the recommended rates. Excessive application increases costs and may be hazardous.

2. Remove aquariums, birds, cats, dogs, and other pets and their food and water dishes before applying insecticides. Keep children and pets off sprayed surfaces until dry.

3. Avoid repeated or prolonged contact of insecticides with the skin and prolonged breathing of spray mist or dust.

4. Never eat or smoke during or after insecticide application without first washing hands and face.

5. If insecticide is spilled on clothing or skin, immediately remove clothing and wash the exposed skin thoroughly with soap and water wash contaminated clothing separately.

6. Store insecticides under lock and key. Keep them in closed, labeled original containers in a dry place where they cannot contaminate foodstuffs and medicines and where pets, children, or irresponsible persons cannot reach them.

7. Dispose of empty containers and unused sprays in a safe manner as directed by the insecticide label. If no directions are given, puncture or break the container (except aerosols) and either wrap it with several sheets of newspaper and put it in the trash, or bury it at least 18 inches deep in an area where there is no danger of seepage into a water supply.

8. In case of poisoning, take the victim to a physician without delay. If possible, take along the insecticide container involved so the physician can determine the poison(s) and prescribe the proper treatment.