German Cockroach

Description: German cockroaches are 1/2 to 5/8 inches long when mature, light brown to tan and have fully developed wings. The pronotum has two dark parallel bars on it. The adult males are somewhat narrower than the females when viewed from below. The nymphs, 1/8 inch long when they emerge from the egg capsule, are almost uniformly dark except for a light tan area on the back of the second and third segments. As they develop, the light tan area becomes larger until as mature nymphs, they have two parallel black bars separated by a light tan area. The purse-shaped egg capsule of the German cockroach ootheca is light brown in color, 1/4 to 3/8 inch long and typically has 15 to 20 eggs per side.

Biology: During her lifetime, the female German cockroach produces four to eight egg capsules each of which contains 30 to 40 eggs. The female carries the egg capsule partially within her abdomen until just before the nymphs are ready to emerge. Approximately one to two days before hatching, she drops the egg capsule in a protected area. If the egg capsule is dropped prematurely, the developing roaches inside die of dehydration. Nymphs molt six to seven times before becoming adults. This requires about 103 days; thus allowing three to four generations per year. Adults live to 100 to 200 days. Established German cockroach populations consist of approximately 75% nymphs.

Habits: German cockroaches are the most common household insect in the Philippines. This pest typically infests kitchens and bathrooms but will live anywhere inside heated structures in which there is food, water and harborage. They rarely are found outdoors and then only during warm weather. German cockroaches gain entry into structures in grocery bags, cardboard boxes, drink cartons, infested equipment such as used refrigerators, toasters, microwaves, etc. Cockroaches feed on all types of human food, as well as on pet food, toothpaste, soap, glue, etc.

German cockroaches are active at night, leaving their harborage areas, e.g., under cupboards, behind cabinets, in wall voids, and around motor housings in appliances where they spend 75% of their time. At most, only one third of the population forages at night. Observation of foraging cockroaches during the day is a good indication that there is a tremendous population. Cockroaches congregate in harborage sites; but as the population increases, over crowding forces some of them to relocate.

Control: Because German cockroaches typically are brought into structures, potentially infested products should be closely inspected. Many types of cardboard and plastic sticky traps are available to help pinpoint sources of cockroach infestation and to monitor areas about which occupants have complained but infestations can not be visually detected. Sticky traps are not intended for control but, rather to guide and evaluate control efforts as part of the inspection process. Visual inspections can be conducted using a flashlight and aerosol pyrethrin to flush cockroaches from their harborages.

An effective cockroach management program depends on good sanitation to eliminate the food, water and harborage they need for survival. Cleanup to reduce cockroaches in the home and office environment must focus mainly on the food residue in and around coffee machines, microwave ovens, stoves, refrigerators, trash cans, furniture and areas where exposed food is stored. It is critical to reduce clutter as cockroaches like to hide in stacked boxes, cartons, and stored paper and cardboard materials, especially in dark, damp locations near food. Vacuum cleaning can be used to physically remove exposed cockroaches.