Cockroaches in Adelaide homes: three species, three different inspections

Adelaide hosts three pest cockroach species. The most-flagged in residential inspections is the German cockroach: small (1.2 to 1.5 cm), light tan with two distinct dark stripes behind the head, fast, and exclusively indoors. German cockroaches breed continuously, with one female producing up to 400 offspring per year. A small initial population becomes a serious infestation in months, not years.

American cockroaches are the second species inspectors flag. They are much larger (3.5 to 4 cm), reddish-brown, capable of short flights, and overwhelmingly found in subfloors, drains, sewers, sump pits, hot water service enclosures, and dark damp outbuildings. Their presence indoors usually traces back to a drain, sewer access point, or subfloor entry route. They are most active in summer when warmth and humidity drive movement up through the building.

Australian cockroaches are similar in size to American but with distinct yellow stripes on the front wings. They live mostly outdoors (gardens, compost bins, woodpiles, wall cavities, eaves) and enter the home only opportunistically. Their presence inside is more of a "house in good condition with one open door" issue than a serious infestation signal.

German cockroaches: warm, dark, narrow voids close to food and water. The classic harbourage list is inside fridge motor housings (a constant 30 degrees C), behind dishwashers, inside microwave bases, in kettle bases, behind cupboard kickboards, inside hollow door cavities, in cracks behind splashbacks, around the underside of bench tops, and inside any cluttered pantry storage. They also exploit shared infrastructure in apartments: shared wall cavities, plumbing chases, and rubbish chute access.

American cockroaches: subfloors are the headline harbourage. Inspectors check subfloor crawl spaces, sump pits, sewer access points, around hot water services, inside drain pits, under bath waste pipes, around floor wastes in laundries and bathrooms, in basement storage areas, and in dark damp outbuildings. Internal sightings usually trace to a defective drain seal or open sewer overflow relief gully.

Australian cockroaches: mostly outdoors. Inspectors check woodpiles, compost bins, garden mulch, around outdoor lights (attracted at night), inside garden sheds with stored timber, behind external cladding, in eave cavities, and in wall cavities of older fibro and timber-framed homes.

Shared structural harbourage: apartments and units share a single cockroach population across the building structure. Inspectors flag this for tenants and owners alike because individual-unit treatment rarely succeeds without building-wide coordination.

Repeated supermarket failure: two or more rounds of shop-bought bait or spray that have not stopped the activity. The harbourage is wider than the product can reach.

Large cockroaches indoors: the reddish-brown American or Australian species rarely respond to over-the-counter products. Their harbourage is structural (drains, subfloors, outdoors) rather than appliance-based.

Apartment or unit infestation: shared cockroach populations across a building need building-wide coordination. The inspection is the documentation that triggers strata or property-manager action.

Commercial food premises: any visible activity in cafes, restaurants, takeaways, bakeries, supermarkets or food manufacturers needs a compliant inspection report for health-authority requirements.

Pre-purchase: document existing activity and underlying conducive conditions before contracts exchange. Drain remediation and subfloor ventilation upgrades are negotiable.

Asthma or allergy in the household: any household member with asthma or known cockroach-allergen sensitivity warrants prompt professional assessment of any visible activity.