Pesticides
Pesticides are substances, or a mixture of substances, intended to prevent, destroy, repel or mitigate any pest. They kill organisms by exerting an effect that interferes with the normal life-sustaining processes. Early types of chemical pesticides were sourced from inorganic minerals (sulphur, arsenic, mercury, lead and lime), or from organic plant material (nicotine, pyrethrum, oxalic acid and garlic).
Extremely early users of a pesticide were the cavemen, who burnt animal dung to keep away mosquitoes! The first known crop pesticide was elemental sulphur dusting; which was used about 4,500 years ago in ancient Mesopotamia.
Perhaps the biggest step forward in the development of pesticides occurred in the 1940s, when DDT was used with great success in the second half of World War II to control malaria and typhus among civilians and troops. After the war, DDT was made available for use as an agricultural insecticide, and its production and use skyrocketed.
Although there are benefits to the use of pesticides, some also have drawbacks, such as toxicity to humans and other animals. Many of the most dangerous and persistent organic chemicals in the world are pesticides. These include DDT, which was banned for agricultural use in Australia in 1987.
Since the 1970s, ongoing attempts have been made to widen the gap between toxicity to insects and toxicity to humans and other mammals. In some instances, this has been achieved with remarkable success.
Types of pesticides
The word “pesticide” comes from the Latin pestis (a plague, pestilence or contagious disease) and cidere (to kill). The term “pesticide” is a broad one, which embraces both generic and particular types.
Particular pesticides are usually named by starting the name with the target organism. The following is a partial list of pesticides:
• Rodenticides – rodents (rats, mice)
• Miticides (acaricides) – mites and spiders
• Herbicides – weeds
• Bactericides – bacteria
• Algicides – algae
• Fungicides – fungi
• Molluscicides – molluscs (snails, slugs)
• Avicides – birds (from Latin avis)
• Insecticides – insects
o Ovicides – eggs (from Latin ovum)
o larvicides – larvae
• Pediculicides – lice
• Piscicides – fish (from Latin piscis)
• Termiticides – termites
