There are three different types of insecticides: systemic insecticides, contact insecticides, and ingested insecticides. All are either natural (organic), man-made (synthetic) formulas, or preparations that are used to control or kill unwanted insects. Although insecticides have widespread use in agricultural applications, natural (organic) formulas have been used in homes for centuries. The 20th century saw the introduction of many man-made (synthetic) formulas that have been used for controlling pests in residential and workplace settings.
The most common application for systemic insecticides is through soil drenching. The insecticide is introduced into the soil where it is absorbed by plant roots. It then moves up through the plant to external areas (leaves, twigs, fruits, branches), where it lays on the plant surface area and is poisonous to any insects that come chewing on the plant.
Contact insecticides act like “bullets” aimed at a target and can only kill insects that are hit by its application. Common household insect spray acts much like a contact insecticide. Because this type must directly hit the insect, it is ineffective as a preventative insecticide.
Many other common household pest control substances are ingested insecticides that are placed throughout the home where insects will ingest the poison. Typical rat and roach poisons are ingested insecticides that are available everywhere from supermarkets to convenience stores.