American Cockroach

Structure, Appearance and Characteristics Adults:

One of the largest of our pest species.
Approx. 35-40mm in length.
Reddish brown in colour.
Light markings on thorax.
Pale yellow border on pronotum.
Wings completely cover abdomen.
Chewing mouthparts.
Nocturnal.
Will fly on occasions.
Good gliders.
Will travel a long way from their breeding areas to feed.

Nymph (The Young):

Look similar to adult but wingless.
Greyish-brown in colour until later instars (moults) which become more like the adult colouring.

Life Cycle

Gradual / Incomplete metamorphosis (egg – nymph – adult). Eggs are encased in an egg capsule (Ootheca). Female carries egg capsule (Ootheca) up to 4 days then deposits the capsule near a food source, in crevices, on walls, or under workable material such as moist wood, so as to camouflage it. Eggs per capsule: 12-16 (in two rows). Incubation period: 38-55 days. Nymphal period: 160-971 days, 400 days (avg). Nymphs normally moult 7-13 times to reach adulthood. Females may produce 6-90 egg capsules in a lifetime. Adult lifespan: up to 2 years.

Habitat

Found in homes, apartments, supermarkets, food processing plants, restaurants, hospitals and commonly found on ships, subfloor areas, sewers, grease traps, wall and roof voids. Favours warm, humid environments. Avoids light where possible. Thrives in temperatures greater than 20 C. Tends to live outdoors in warmer climates and indoors in colder regions. Dispersal of the population is often facilitated by egg cases glued to packaging or boxes which are then transported to a different region.

Food

Omnivorous. Scavenger. Prefers decaying organic matter. Adults can live for approx. 2-3 months without food (assuming water is available), or less than 1 month without food or water. Will feed on book bindings, manuscripts, clothing, sweet foods.

Pest Status

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 status applies 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 targeted 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.