Final answer:
German roaches should be treated by applying pesticides with a residual treatment into all the crack and crevices in an infested area.
Step-by-step explanation:
The pests that should be treated by applying pesticides with a residual treatment into all the crack and crevices in an infested area are German roaches. German roaches are one of the most common types of roaches found in homes and they tend to infest areas with high moisture and food sources. By applying pesticides into cracks and crevices, the residual treatment can reach their hiding places and help control the infestation.