Conventional Insecticides -- The Killer Chemicals

Conventional insecticides are among the most popular chemical control agents because they are readily available, rapid acting, and highly reliable. A single application may control several different pest species and usually forms a persistent residue that continues to kill insects for hours or even days after application. Because of their convenience and effectiveness, insecticides quickly became standard practice for pest control during the 1960's and 1970's. Overuse, misuse, and abuse of these chemicals have led to widespread criticism of chemical control and, in a few cases, resulted in long-term environmental consequences.
The effectiveness of an insecticide usually depends on when and where the pest encounters it. Most insecticides are absorbed directly through an insect's exoskeleton. These compounds are known as contact poisons because they are effective "on contact". Other insecticides act as fumigants. They are released in the vapor state (as gases) and enter the insect's body through its tracheal system. Fumigants are most effective when they are used in an enclosed area such as a greenhouse, a warehouse, or a grain bin. Still other compounds must be ingested before they have an effect. These are known as stomach poisons. They often work more slowly than fumigants or contact poisons, but they are still useful for certain types of pest control in homes and businesses