This is the first of several posts intended to educate readers about pesticides. This week we’ll focus on their history. In future posts, we’ll take a look at different kinds of pesticides, how they work, safety tips, myths and misconceptions, and related topics.
What is a pesticide?
Simply put, a pesticide is any substance used to control pests. It’s a broad term, and includes herbicides, which are used to control unwanted plants. In this series we’ll focus primarily on insecticides. When most people think of pesticides, they probably assume that they’re used to kill pests; however, effective pest control often involves repelling pests.
It’s also likely that many people think of pesticides as a relatively recent invention. Not true. Humans have been using pesticides for thousands of years, primarily to protect crops.
- Sulfur was used as early as 2,500 BC in ancient Sumer (near the modern-day Persian Gulf) to control insects and mites.
- The ancient Chinese controlled body lice with mercury and arsenic.
- Many cultures have used salt and/or sea water to control weeds (or to render soil useless in times of war).
- The Romans burned sulphur to kill insect pests.
- Persians used pyrethrum powder, made from dried Chrysanthemum flowers, to protect stored grain.
- In the third century BC, the Chinese burned herbs to repel mosquitoes.
Farmers began to resort to more toxic chemicals in later centuries, and treated crops with substances like arsenic, mercury, and lead. Natural insecticides included pyrethrum and rotenone.
The Pesticide Century
If one century can be remembered as the century of pesticides, it is the 20th. Researchers developed numerous synthetic pesticides of varying effectiveness; some were branded and sold without any information about the active ingredient(s). In the early 1900s, sodium chlorate and sulphuric acid were popular, as well as industrial byproducts like creosote, naphthalene, and petroleum oils. In 1939, Paul Muller discovered that dichlorodiphenyltrichloroethane (DDT), which had been first synthesized in 1874, could be used to control mosquito populations and combat malaria. The discovery earned him the Nobel Prize.
Other pesticides used in the mid- to late 1900s were aldrin, dieldrin, chlordane, parathion, captan, and endrin. (Those of the World War II generation might remember Black Flag, which combined several insecticides, including DDT and chlordane.)They were inexpensive and seemed to work very well — perhaps too well. Concerns about misuse led to new restrictions on the manufacture and application of pesticides, enforced by the Environmental Protection Agency (EPA), which was founded in 1970. Numerous pesticides have since been banned to protect the environment and human health, though the EPA has frequently been accused of making decisions based on politics rather than science.
The 21st Century and Beyond
In this era of strict regulations, the most popular pesticides include organophosphates, carbamates (e.g., Sevin dust), deltamethrin, fipronil, and pyrethrins (e.g., Talstar). As opposed to banned pesticides that remained active for years, many of these break down within months.
Manufacturers continue to research and develop new pesticides, with the goal of making them safer and more effective. We’ve seen many changes in the pest control industry in the last four decades; what will the future hold? Stricter regulations, fewer legal pesticides, and more pests? Resistant populations of insect pests? Perfect pesticides that will harm only their intended targets?
We’ll have to wait and see.