Non-residual sprays are most useful for finding the location and size of cockroach infestations. A non-residual spray by itself will not provide adequate control, but when used with a residual insecticide a high degree of control can usually be achieved. A small amount of spray squirted into harborage areas forces rapid movement of cockroaches onto surfaces previously treated with the residual material. Cockroaches can also be controlled with insecticidal dusts. Dusts are useful because they may be placed deep into cracks and crevices, wall voids under large appliances and furniture, around electrical outlets and wiring, on very smooth or porous surfaces, and in other areas where spray applications might be impractical or unsafe.
Dusts generally provide longer residual control than sprays but become ineffective in wet locations.
When properly used, dusts should leave a barely visible, uniform deposit on the treated surface. Sometimes a combination of dust and spray treatments is more effective than either alone. When used with sprays, dusts should be applied after the spray has dried. Traps Trapping is an effective way to reduce cockroach populations, especially when used along with preventive and insecticidal measures. Trapping also can determine harborage areas and infestation severity, monitor effectiveness of chemical controls, and detect population increases which may require insecticide treatment.