hat pesticides generally kill not only the pest of concern, but also a wide range of other organisms, including beneficial insects and other pest predators. Once the effect of the pesticide wears off, the pest species is likely to recover more rapidly than its predators because of differences in the available food supply. Previously unimportant species may also become significant crop pests when their natural predators are killed by pesticide applications.Another drawback to the increasing pesticide use is the development of resistance in pest species. The individual pests that survive pesticide applications continue to breed, gradually producing a population with greater tolerance to the chemicals applied. Presticides, therefore, have to be used in ever increasing quantities or replaced with new chemicals to adequately control pest populations.Following World War II, DDT and related chlorinated hydrocarbons were introduced as potent new pesticides and were used throughout the world for protection of agricultural crops, as well as control of mosquitoes, lice, and other human pests. In 1962 Rachel Carson's book Silent Spring brought public attention to the fact that these organic compounds are highly persistent in the environment and accumulate in animal tissues, causing water contamination, fish kills, and decline of some bird populations. DDT was banned for agricultural use in the United States in 1973, and since that time it and similar chlorinated hydrocarbons have been replaced by less persistent, but more acutely toxic, compounds. Because some of these new pesticides are highly soluble in water, they may leach to groundwater underlying farming regions. In Suffolk County at the eastern end of Long Island, for example, 13 different pesticides have been measured at least once in groundwater samples. Twelve percent of the wells tested in Suffolk County have exceeded the drinking water guideline for aldicarb, a highly soluble pesticide ...
