The German cockroach is the cockroach of concern, the species that gives all other cockroaches a bad name. German cockroaches contaminate food or food products with their feces and defensive secretions, physically transport and often harbor pathogenic organisms, may cause severe allergic responses, and in extremely heavy infestations have been reported to bite humans and feed on food residues on the faces of sleeping humans.
Adults are pale to medium brown and are 10 - 15mm. Males are light yellowish brown in colour and have a longer supra-anal plate, while females are darker and have a stout abdomen. Both sexes have well developed wings but never fly.
Nymphs are black with a light stripe up the mid-dorsum. All stages have 2 parallel bands on the pronotum separated by a lighter stripe.
This species reproduces the fastest of the common pest cockroaches. A single female and her offspring can produce over 30,000 individuals in a year, but many succumb to cannibalism and other population pressures. Egg laying occurs more frequently during warm weather. The female carries around a light tan egg case (about 7 - 9 mm long) until 1 to 2 days before it hatches, when she drops it. Sometimes the egg case hatches while it is still being carried by the female. Each egg case contains about 30 young, and a female may produce a new egg case every few weeks.
The nympal development period takes about 30 days, in which they will molt 6 - 7 times in this period. The adults can survive for about 100 days.
They are active at night but hide in cracks and crevices during the day. German cockroaches usually hide in areas close to moisture and food. They are found infesting restaurants, hotels and urban apartments, usually in dark, secluded harborage areas such as under cupboard, behind refrigerator etc.
They prefer to rest on wood rather than on metal or other smooth surfaces. Large infestation does occur on metal surfaces when there are limited resting surfaces.
Sanitation is critical in roach control. Clean up spilled foods and liquids. Avoid leaving scraps of food on unwashed dishes and countertops overnight. Keep food in tightly sealed containers, rinse cans and bottles before putting in the trash, and transfer garbage outdoors into roach-proof receptacles away from the house. Leftover pet food should not remain in the feeding dish overnight.
Insecticides are most effective in controlling cockroaches when combined with sanitation and exclusion practices that limit the cockroach's ability to establish or reinvade; chemical control alone will not solve the problem.
Baits are formulated as pastes, gels, granules, and dusts. The most popular use of baits in homes is within bait stations, which are small plastic or cardboard units that contain an attractive food base along with an insecticide. Bait gels are placed in small dabs in cracks and crevices where cockroaches will find it. Baits can be quite effective for long-term control of cockroaches unless the cockroaches have other food sources available to them.