Cockroaches range in size from nymphs 1/8 inch long to Palmetto Bugs 2 inches long. They feed on almost any type of material, including bar soap, paper, glue and food residue. They can be carried into homes in bags or boxes and, once established, breed prolifically. German cockroaches prefer dark, warm habitats, while American and Oriental cockroaches seek out cool, damp environments, according to University of Minnesota entomologists Jeffrey D. Hahn and Mark K. Ascerno. Good sanitation and the repair of sources of moisture help to control cockroach infestations in the home.
Boric acid is a naturally occurring mineral mined in several areas of the world. It is useful as an insecticide because it works as a stomach poison on cockroaches and other insects. Generally, boric acid is made into bait with a sweet or greasy substance that entices the cockroaches to feed on it and carry it back to the nest. When the other roaches feed on the boric-acid bait, the colony dies.
Silica gel is a finely ground powder inserted into cracks and crevices where cockroaches have been seen. It sticks to the insect's body, absorbing the cockroach's protective waxy coating and dehydrating its body fluids, according to University of Florida entomologists D. M. Miller and P.G. Koehler.
Diatomaceous earth consists of the fossilized skeletons of tiny marine creatures. These are processed into a fine powder that has very small, sharp edges that, when spread in areas where cockroaches have been seen, can cut and scrape the exoskeleton of the insect, causing it to desiccate and die. The material is slow-acting, so cockroaches walk through where it is spread and carry it back to the nest where other insects come in contact with it.
Neem oil is extracted from the seeds of a Southeast Asia tree. It contains two chemicals that possess insecticidal properties: azadirachtin and salannin. These compounds work as feeding deterrents and growth regulators on immature cockroaches. It has low toxicity.