Pest control tactics were mentioned occasionally in writings of the ancient Chinese, Sumerian, and Egyptian scholars.   Many of these tactics were embedded in religion or superstition, but a few had real scientific merit.   Predatory ants, for example, were used in China as early as 1200 B.C. to protect citrus groves from caterpillars and wood boring beetles.   Ropes or bamboo sticks tied between adjacent branches helped the ants move easily from place to place.   A passage in Homer's Iliad (8th century B.C.) describes the use of fire to drive locusts into the sea, and the ancient Egyptians organized long lines of human drovers to repel swarms of invading locusts.   Pythagorus, a Greek philosopher and mathematician, was credited with clearing malaria from a Sicilian town during the 6th century B.C. by instructing its residents to drain the marshes.   Chemical substances that purportedly killed or repelled insects were in common usage.   Many of these were of questionable value, but some worked, and a few are still in use today.   Some of the inorganic compounds, such as sulfur and arsenic, have well-established insecticidal activity.   And modern science has only recently come to recognize that many plant extracts used by ancient apothecaries (e.g, lemon oil, wormwood, hellebore, fleabane, etc.) do indeed contain compounds with useful activity against insects.

There was very little progress in pest control during the dark ages.   Ignorance and superstition abounded.   For what it was worth, St. Bernhard excommunicated the flies of his parish in 1121.   In a book entitled "Natural History", Ferrante Imperato (1599) gave a prescription for eliminating flies from a dwelling:

"... draw the image of a fly ... on a copper plate during the second half of the constellation of Pisces ... then bury it in the center of your house (during) the first half of the constellation of Taurus."

Since the late 1800's, entomologists and chemists have made outstanding progress in the technology of pest control.   Today's arsenal of weapons is large and diverse, encompassing legal, cultural, physical, genetic, and biological tactics, in addition to the well-known chemical pesticides.   In general, all of these tactics work in at least one of the following ways:

• They kill the pest directly -- usually by exposing it to lethal substances or unsuitable environmental conditions.
• They reduce the reproductive potential of a pest population -- often by modifying its environment (biotic or abiotic) or by restricting its movement.
• They modify the pest's behavior to make it less troublesome (attract it, repel it, confuse it, exclude it, mislead it).

Most of the control tactics that are commonly used today can be grouped into two broad categories:   natural controls and artificial controls.   By definition, a natural control may be any environmental factor that keeps a pest population below its economic injury level.   Examples might include geographic barriers, cold temperatures, or natural enemies that keep population growth in check.   Artificial controls, on the other hand, employ products or processes of human origin to modify a pest's distribution, behavior or physiology.   Fly swatters and insecticides are two obvious examples.   But as is often true in biology, there are some control strategies that seem to straddle the line, exhibiting characteristics of both groups or not fitting neatly into either category.   In fact, some of our most effective tactics are natural controls that we can improve, enhance, accelerate, or augment by appropriate human intervention.