Pesticides can kill roaches and other pests many ways, but the most common method of elimination is through disruption of the insect's nervous system, according to the Environmental Protection Agency. Most roach sprays contain nerve-destroying agents similar to those used in chemical weapons, but they are used in much smaller doses to prevent harm to pets and humans, according to Wessels Living History Farm.
The three most common types of pesticides are organophosphates, carbamates and pyrethroids, and each works by disrupting the nervous system of the target pest, the EPA said. This disruption prevents them from moving or feeding, and it eventually leads to their death. Roach sprays also may include an insect growth regulator designed to contaminate eggs and larvae, preventing them from hatching and reaching adulthood. Many roach sprays are designed to have a delayed effect, allowing the cockroach to enter the structure walls and contaminate the entire nest before dying.
Cockroaches have proven that they can adapt to insecticides, and they also can develop a high resistance to particular agents used in over-the-counter products and by pest control companies, according to the University of Kentucky. For that reason, using multiple types of pesticides, baits or other forms of pest control at once is the best way to handle a roach infestation.