German Cockroach

Structure, Appearance and Characteristics

Adults:

• Approx. 12-16mm in length.
• Pale brown with two longitudinal streaks on the pronotum.
• Have wings but rarely fly.
• Chewing mouthparts.
• Nocturnal but may be seen during daytime if population is large.
• High reproductive potential because of speed of life cycle and number of young in comparison to other species.
• This presents an increased tendency for this species to become resistant to chemical through ‘selection’.
• Very active.

Nymph (The young):

• Look similar to adult but wingless.
• Darker brown, nearly black in colour.
• A single light strip down the middle of the back is normally prominent.

Life Cycle

Gradual / Incomplete metamorphosis (egg ¡V nymph ¡V adult). Eggs are encased in an egg capsule (Ootheca). Female carries egg capsule (Ootheca) until eggs are ready to hatch. Eggs per capsule: 30-48. Incubation period (24„aC): 28 days (avg). Nymphal period (24 C): 40-125 days. Nymphs normally moult 7 times to reach adulthood. Females may produce 4-8 egg capsules in a lifetime. Adult lifespan: up to 1 year.

Habitat

Found in homes, apartments, supermarkets, food processing plants, restaurants, ships. Favours warm, humid environments. Seeks cracks and dark crevices for harbourages, avoids light. Favours areas close to food and water such as kitchens and other food handling areas, however can be found in other areas which will indicate heavy infestation. Often moved to new habitats by food packages, cardboard boxes etc.

Food

Omnivorous. Scavengers. Prefers fermented foods. Adults can live for approx. 1 month without food (assuming water is available), or less than 2 weeks without food or water. Nymphs will die within 10 days without food. Have been known to feed on glue and soiled clothing.

Economic Impact / Nuisance

Presence can cause anxiety or stress. Secretions can affect some humans (e.g. allergic reactions such as asthma). Dense populations can leave a distinct odour. Food and utensils can be contaminated with droppings, cast skins, empty egg cases and vomit marks. A number of pathogenic organisms have been associated with cockroaches. Their ability to act as vectors of pathogens is still a matter of controversy. This is mainly because that transmission can only occur indirectly via contamination of food and utensils. Pest statusapplies equally to nymphs and adults.

Control

Cockroaches have aggregation characteristics which builds a more suitable environment to inhabit. They favour cracks and crevices for harbourages where they can contact the top and bottom surfaces with their body. They do not leave their harbourages except for food, water and mating. Their aggregation characteristic can be used against them, since finding a harbourage will yield more than one individual. Pheromones are not volatile, so contact with other individuals in the population is necessary, which can help spread insecticide to some degree.

Control should be targetted at their harbourages since they stay in these areas for large amounts of time. Physical exclusion (e.g. caulking up cracks) is useful since the cockroach population is proportional to the number of harbourages available. Chemical treatments into cracks and crevices is also valuable since prolonged contact with treated surfaces will yield a high mortality rate. Applying proper hygiene measures can also be useful, forcing the cockroaches to travel further to find food and water, which increases the chances of contacting treated surfaces outside harbourage areas.