Remember German cockroaches will spend most of their time in cracks and crevices, and emerge at night for food. As a result, sound control practices should include sealing those harborage areas with a caulk or sealant to exclude the cockroaches, not just applying a pesticide.
In many areas, you can treat the crack or crevice with a dust insecticide (such as a borate powder) before you apply the sealant. Baits also can be used for the control of these cockroaches if applied into or on labeled locations. Liquid and aerosol products, generally labeled for crack-and-crevice applications, also are labeled for control.
For American cockroaches and other large cockroach species, you first must identify the species to determine the proper control protocols. Each species might have different preferences for habits, harborage and food. Some will infest attic areas, basements and boiler rooms, and even enter the structure from outside.
Identify the species and, upon inspection, determine the source of infestation and provide the proper control measures. Such measures might include closing or sealing access to the structure to prevent entry from outside or applying baits to the exterior of the structure, attics or boiler rooms. Liquid or aerosol products also can be used, per individual label applications.