Asian Cockroaches

Order:  Blattodea
Family:  Blattidae
Scientific Name:  Blattella asahinai Mizukubo

The Asian cockroach is the most recent cockroach species introduced (circa 1980) into the United States, increasing the total number of species to 66.  The Asian species is found throughout central Florida and has the potential to spread to other temperate regions.

Three Blattella species are found in the United States:  Asian, German (B. germanica) and field (B. vaga).  Without question, German cockroaches are the most problematic due to their impact on human health, food safety and aesthetics.  The Asian cockroach, in contrast, is only an occasional invader, mainly due to its attraction to light.  Outdoors, however, these cockroaches tend to be the predominant species with estimates of more than 250,000 per acre.

Identification

Asian cockroaches look like German cockroaches; even taxonomic experts have difficulty distinguishing the two species.  Asian cockroach adults are about ½ to 5/8 inch (13 to 16 mm) long, and light brown to tan in color, except for two dark longitudinal bands on the pronotum (i.e., the dorsal area behind the head).  Asian nymphs are typically pale along the abdomen’s lateral margins, whereas German nymphs are dark in this area.  Asian cockroach egg capsules are smaller than the German’s, but they average the same number of eggs.

The most accurate method of species identification is gas chromatography, an elaborate chemical test.  This technique can identify any life stage of a cockroach, even if body fragments are used.  In the field, PCOs can use behavioral differences to distinguish the two species.  Asian cockroaches live primarily outdoors in leaf litter or grassy areas; they are very active fliers and are attracted to light.  In contrast, German cockroaches live primarily indoors; they are very weak fliers, fluttering at best, and are repelled by light.  Because Asian cockroaches are attracted to light, once they enter a structure, they move to areas of brighter light, giving the appearance of following occupants as they move through the building turning on lights.

Life Cycle and Habits

The Asian cockroach undergoes simple, or gradual, metamorphosis, which has three life-cycle stages: egg, nymph, and adult.  Development is very similar to that of the German cockroach.  The female carries the egg capsule until one to two days prior to hatching.  The female produces five to six egg capsules, each containing 38 to 44 eggs.  The life expectancy of adult Asian cockroaches is much shorter than Germans, mainly due to increased environmental exposure.  As a result, most females bring only two egg capsules to maturity.  Developmental time from egg to adult is about 65 days.

The Asian species can interbreed with German cockroaches, resulting in viable offspring that can fly.  While interbreeding readily occurs in the laboratory, it rarely occurs to any appreciable extent in the field, primarily due to behavioral differences.

Control

The best control method for this species is prevention.  Because Asian cockroaches are attracted to light, changing the lighting around structures significantly reduces their entry.  To reduce attraction, use sodium vapor lights or yellow incandescent bulbs, and locate lights away from but directed toward the structure.  In addition, minimize the use of interior lights near doors and windows, and keep drapes or shades closed at night.  Inspect all screens and door seals to ensure that they are in good condition and adequately protect the opening.

This species is susceptible to virtually any insecticide.  Outdoor applications targeting preferred harborages can effectively knock down populations to acceptable levels.  One of the best techniques is to use one of the scatter baits registered for outdoor cockroach control.  These products can be more easily applied in areas with heavy undergrowth, which is not readily penetrated by liquid formulations.