Cockroaches Fact Sheet No. 5.553 Insect Series|Home and Garden by F.B. Peairs* Cockroaches are among the most Quick Facts undesirable insect intruders in the home. They are associated with filth and unsanitary • Cockroaches are associated conditions, although they occasionally invade with filth and unsanitary the best-kept homes. conditions. Though known to carry various disease • Known to carry disease organisms, cockroaches have not been organisms, they have not associated with any major disease outbreaks been tied to major disease in this country. The insects also produce a outbreaks in the United secretion that has a repulsive odor and can States. affect the flavor of food. Cockroaches can • Egg cases, nymphs and cause allergic reactions when sensitive people adults can be found in an come into contact with contaminated food or infested area. house dust. Figure 1: Brownbanded (top) and American • Eliminate unnecessary (bottom) cockroach egg cases. sources of water, food and hiding places. Biology • Use traps, residual and Three cockroach life forms can be found non-residual insecticide in an infested area. The egg case is the size sprays, and insecticide dusts and shape of a bean and contains 10 to 20 to control or eliminate cockroach eggs (Figure 1). The female may cockroaches. carry the eggs around until just before they hatch or, in some species, she may hide them in some protected area. As the eggs hatch, young cockroaches, or nymphs, emerge. Similar in shape and color to the adults, they are smaller and wingless. Their habitats Figure 2: German cockroach. (Photo from the K. Gray Image Collection, Oregon State University.) and food preferences are the same as those of adults. Cockroaches are active at night, so smaller species, 1/2 inch when full grown, it daytime observation is a good sign of a heavy is light brown with a pair of parallel brown infestation. They prefer protected areas, bars between the head and the front of such as cracks and crevices, to rest and hide. the wings (Figure 2). This species usually Although cockroaches prefer starchy foods is associated with buildings where food is and meats, they will eat anything of plant or prepared or stored. It commonly migrates animal origin. from infested areas into nearby dwellings or may be carried in on food containers. Favorite home habitats are warm, moist Common Species areas, such as kitchen sinks and appliances, There are more than 50 species of bathroom sinks, and furnaces. cockroaches in the United States. However, The American cockroach is the largest only five are likely to be found in Colorado. pest species found in Colorado – up to 2 © Colorado State University The German cockroach is the most inches long. It is mahogany-colored with a Extension. 7/95. Revised 6/12. yellow margin around the head and around troublesome of all cockroaches. One of the www.ext.colostate.edu the shield behind the head (Figure 3). *Colorado State University Extension entomologist Although occasionally found in homes, the and professor, bioagricultural sciences and pest American cockroach more commonly is management. Artwork by Thomas J. Weissling. 6/2012 found in warm, moist areas of industrial or Prevention and Sanitation Insecticides are poisons. Treat them If cockroaches are migrating into as such. a building or from another part of a Boric acid powder is relatively safe for building, install weather stripping and humans, but do not expose children caulking where plumbing passes from and pets to it. infested areas into uninfested areas. Eliminate hiding places. For example, Baits are long lasting and are most caulk cracks and crevices in dark, moist effective when placed in small areas to discourage cockroaches. Inspect amounts in many locations. items brought into a building, especially Figure 3: American cockroach. (Photo from the K. Gray Image Collection, Oregon State food containers, furniture, appliances and University.) clothing. The adults and young are easy to commercial buildings. Furnace or boiler recognize. Because some cockroaches glue rooms, sewers and heat tunnels are favored their egg cases to various surfaces, take environments. particular care to look for the eggs. The brownbanded cockroach is similar Cockroaches need food, water and in size and color to the German cockroach. shelter. Water is particularly important, It can be distinguished by the lack of brown which is why infestations are most common bars on the shield in front of the wings and in kitchens and bathrooms. Make any by the presence of two light bands across plumbing repairs and modifications needed the wings and abdomen (Figure 4). It to eliminate as much standing water prefers a warmer, drier environment than as possible. the German cockroach and often is found Do not allow food particles to in ceilings, light fixtures, furniture and accumulate in areas accessible to Figure 4: Brown-banded cockroach. (Photo appliances, especially televisions. cockroaches. Common feeding areas from the K. Gray Image Collection, Oregon State The oriental cockroach is intermediate include unwashed dishes, pet dishes, University.) in size between the German and the uncovered pet food containers, litter American cockroach and much darker. The boxes, waste containers, and areas under adults have wings that do not reach the end refrigerators, stoves, sinks and furniture. of the abdomen (Figure 5). Many consider Repair faulty plumbing and eliminate it the most repulsive common cockroach, unnecessary sources of water. Reduce primarily due to its strong odor. This shelter for cockroaches; do not store species prefers cool, damp, dark areas. For unnecessary newspapers, boxes, rags and this reason, it often is called a “water bug.” similar items that provide hiding places. Common habitats include sewer drains, damp crawl spaces, basements and cellars. Detection Infestations are most common in the spring Detection is an important element of and fall. cockroach control. Cockroaches tend to The wood cockroach prefers the concentrate in certain areas. Controls are Figure 5: Oriental cockroach. (Photo from the K. outdoors and usually is found in wood more effective if they are targeted at these Gray Image Collection, Oregon State University.) piles, in dead trees and under bark. spots. Cockroach traps, small, open-ended Attracted to lights, it occasionally enters boxes, contain an attractant and sticky Chemical Control homes and causes great alarm because it is substance that retains the insects once they Cockroach insecticides include residual so easily confused with pest cockroaches. enter. Use them to locate infestations and sprays, nonresidual sprays, dusts and baits. The wood cockroach has a white band that to determine when populations require Use a combination for effective chemical runs around the head and the shield behind additional treatment. Traps can be effective cockroach control. the head. Usually it does not survive or in catching the occasional invader, but they All cockroach insecticide labels multiply indoors. will not eliminate established colonies. contain important instructions and Traps are most effective when placed precautions to ensure effectiveness and against walls under sinks, in cabinets and Cockroach Management to protect the safety of humans and pets. in basement corners. If two nights pass Read, understand and follow all label The three keys to effective cockroach without a capture, move the trap to another instructions when applying any residual management are prevention and sanitation, likely area. detection and chemical control. Satisfactory spray, nonresidual spray, dust or bait. cockroach control will not be achieved unless each of these steps is followed. Residual insecticide sprays leave Boric acid powder (also available as have access to insecticides and equipment a toxic deposit on surfaces and will kill a residual spray), available under several that are not available to private individuals. cockroaches for a certain time period, commercial names, is relatively safe for Choose a company with the same care you usually two to four weeks. Apply to cracks humans, but do not expose children and use to select other services for the home. and crevices where cockroaches hide and pets to it. It can cause skin irritations if improperly handled, and it will harm house areas where they walk in search of food. Biological Control Spray until the surface is wet, but avoid plants. Apply boric acid only to hiding overapplications that puddle or run off. places and runways. It is slow acting. Do Biological control uses one organism Insecticides are poisons and should not expect complete control for at least one to control another. Where insecticides be treated as such. Used improperly, they week after application. Boric acid is among are undesirable or it is not necessary can damage linoleum, carpets, drapes the best cockroach insecticides. Combined to eliminate cockroaches completely, and paint. Various insecticides, under with its relative safety, this makes it a good consider a biological control program. a variety of commercial names, are choice for homeowners. Such programs have not been popular in available for residual treatments against Other dusts are based on silica aerogel the past because many find the biological cockroaches. Some products are available or diatomaceous earth. These are applied control agent to be as distasteful as the to homeowners, while others are limited in the same manner as boric acid. They cockroaches. Additionally, insecticide use to licensed pest control operators. Residual may not be as effective as boric acid would have to be minimized or eliminated, insecticide treatments are generally because they are repellent to the cockroach. because the beneficial organism often is effective, but cockroaches, especially However, they can keep the pests out even more susceptible to insecticides than the German, have developed insecticide of certain areas, such as wall voids and cockroaches. resistance in many parts of the country. attics. While boric acid is poisonous, silica Many kinds of organisms attack Nonresidual insecticide sprays aerogel and diatomaceous earth act by cockroaches: toads, bacteria, protozoa, eliminate cockroaches only on contact. rubbing off the protective waxes that cover beetles, mites and wasps. Parasitic wasps They will not eliminate an infestation but the cockroach’s body and cause death by have had the most success. These are are quite helpful when used with residual dehydration. tiny insects, harmless to humans, that treatments. Several short-lasting aerosol Baits can be applied to areas that lay their eggs in the cockroach case. The insecticides contain the active ingredients cannot be sprayed or dusted. They consist eggs hatch into immature wasps that pyrethrins or resmethrin. They irritate of an attractant, such as peanut butter or feed on the cockroach eggs. Wasps can cockroaches and can flush the pests out syrup, and a nonrepellent insecticide, such reduce cockroach numbers dramatically of their hiding places and force them into as boric acid. Baits are long lasting and and keep them at low levels, but they areas treated with a residual insecticide. are most effective when placed in small cannot completely eliminate the problem. This flushing action also is useful to amounts in many locations. Most baits are Parasitic wasps have been used successfully determine whether or not cockroaches are available in child- and petproof containers. in nonresidential office buildings and present. Flushing agents, however, can drive Baits are much more effective if they are warehouses, but not in residential buildings them into previously uninfested parts of the the only food source available. Good where there is much less tolerance of building. sanitation is especially important for this cockroaches and other insects. Insecticide dusts can penetrate type of control. cockroach hiding areas that other References insecticides will not reach. When applied to Professional Pest Control dry locations, they have a longer useful life Cornwell, P.B. 1968. The Cockroach. Volume I. than residual sprays. Some dusts contain If the situation is severe or it is unclear Hutchinson, London, 391 pp. conventional insecticides, while others what to do, professional pest control Cornwell, P.B. 1976. The Cockroach. Volume contain no organic chemicals. services are available. These companies II. Hutchinson, London, 557 pp. employ trained pest control operators and Roth, L.M., and E.R. Willis. 1957. The medical and veterinary importance of cockroaches. Smithsonian Miscellaneous Collection 134(10): 1-147.
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