German cockroaches prefer to live in warm, humid places close to food and moisture sources. They are frequently found in residential and commercial kitchen environments, and bathrooms, so these are the two most likely places for an infestation to occur. It is also likely to find German cockroach dropping in areas they frequent. Droppings may appear as small, dark, “pepper-like” material left on countertops or in drawers. There may also be fecal staining, which appears as dark spots or smears in the corners of rooms, along the tops of doors or around small cracks and openings into walls.

When German cockroach populations are present in large numbers, it may be possible to detect a mild, somewhat “musty” odor.