Pesticides and pest control
Pesticides and pest control involve the management of organisms considered pests, which negatively impact human health, crops, or property. Pests can include insects, rodents, weeds, fungi, and other organisms that disrupt human activities or agricultural production. The use of chemical pesticides surged in the 20th century, significantly enhancing agricultural productivity and protecting properties from pest damage. However, the extensive use of these chemicals has raised environmental concerns, leading to regulations and a shift towards alternative pest-control methods.
Chemical pesticides are classified based on the organisms they target, such as insecticides for insects and herbicides for weeds. They can also be categorized by their chemical composition, with various generations of pesticides evolving over time. The environmental and health impacts of early chemical pesticides, like DDT, prompted stricter regulations and the exploration of biological control methods, which leverage natural predators and parasites to manage pest populations. As awareness of the ecological consequences grows, innovative approaches, including genetic modifications and camouflage techniques, are being researched to provide sustainable pest management solutions.
Pesticides and pest control
Pesticides are agents used to kill or otherwise control organisms that are harmful to humans or crops. In addition to chemical agents, alternative pest-control methods are available.
Background
An animal or a plant is regarded as a pest if it causes a nuisance or harm to humans or crops or otherwise negatively impacts human health, well-being, or quality of life. Pests such as silverfish consume paper and fabrics. Termites cause serious damage to houses and other wooden structures. Weeds, aphids, and snails play havoc with flower gardens. Beetles and fungi attack shade trees, timber, crops, orchards, and stored foods. Mosquitos, ticks, mites, and rodents transmit viruses and other disease organisms to humans.
Pest control is the ongoing process of managing insects, rodents, weeds, fungi, and other pest organisms where their lives intersect human lives. The twentieth century saw a rapid escalation in the use of chemical pesticides, which have become a mainstay of pest control. These chemicals have suppressed pest populations, increased crop yields, protected property, and kept disease in check. However, indiscriminate use of chemical pesticides has damaged the environment, which has led to governmental regulation of pesticides, outright bans on some substances, and increased interest in alternative pest-control methods.
Types of Chemical Pesticides
Chemical pesticides are often classified based on the organisms that they target. Avicides kill or repel bird pests. Rodenticides are for use against rats and mice. Acaracides and miticides target ticks and mites. Insecticides, the largest category of pesticide, are used against insects. Nematicides are used to kill nematodes, soil- and water-dwelling roundworms that are often parasitic on plants and animals. Fungicides are used to treat crops and other plants for fungal (and sometimes bacterial) conditions such as root rot, smut, gall, rust, and blight. Herbicides target the weeds and other unwanted vegetation that encroach on lawns, gardens, crops, and paths. Defoliants are a class of that induces leaf fall from trees and other plants.
Pesticides can also be categorized on the basis of chemical composition. Mineral pesticides such as arsenic, borax, copper, lead, and zinc were among the first pesticides employed by humans; these minerals have mostly been replaced by more efficient chemical compounds. Botanical pesticides are insecticidal substances derived from plants or are synthetic analogs to such substances. These include pyrethrins, chrysanthemum-derived insecticides which are not highly toxic to humans. Chlorinated hydrocarbons, which include chlorine, hydrogen, and oxygen in their chemical makeup, are highly effective poisons that do not readily degrade in the environment. Compounds such as aldrin, endrin, dieldrin, chlordane, and dichloro-diphenyl-trichloroethane (DDT) were widely employed before the environmental implications of their persistence were fully understood. Organophosphate pesticides are organic phosphate compounds that break down in the environment more easily than the chlorinated hydrocarbons, particularly in the presence of water. Examples include malathion, naled, dichlorvos, methyl and ethyl parathion, and diazinon. Carbamates, characterized by carbamic acid, include carbaryl, carbofuran, and methylcarbamate; these compounds degrade more quickly than organophosphates.
Pesticides may be categorized further as selective or nonselective. A selective targets a particular pest, while a nonselective pesticide (also called a broad-spectrum or general-usage pesticide) is toxic to a wide range of organisms and does not confine its effects to the target species once it is released into the environment. Selectively toxic chemicals minimize the pesticide’s impact on the environment. Chemical pesticides are applied in various forms, including wet sprays, dusts, atomizable fluids, low-pressure aerosols, smoke, gases, and seed treatments.
History of Use
The “first generation” of chemical pesticides was the minerals and botanicals. In 1867, farmers in the United States began using Paris green, a then-common pigment containing arsenic and copper, to control outbreaks of the Colorado potato beetle. Lead arsenate was introduced as an in 1892. By the 1920s, pesticide use in the United States had become commonplace, and concerns over arsenical residues in foods had begun to arise.
In 1939, the next generation of chemical pesticides was ushered in with the discovery of DDT’s insecticidal properties. The compound was first disseminated on a large scale during the Naples typhus epidemic of 1943-1944, and it found widespread use during the remainder of World War II. DDT and other potent broad-spectrum poisons were popular pesticides from the early 1940s through the 1960s. However, as concerns mounted over the environmental impact of these chemicals—contaminated watersheds; the dying off of beneficial species coupled with pests becoming pesticide resistant; the accumulation of pesticides in the bodies of higher animals, including humans; and poisoned food chains—use of chlorinated fell into disfavor. Use of DDT and similar chemicals has been banned or restricted in many countries, including the United States.
The disadvantages of chemical pesticides have led to an increased interest in alternative pest-control methods. Biological control agents include microorganisms that are harmful to pests but not to other life; natural predators and parasites; and the release of large numbers of laboratory-sterilized insects, which then mate with normal insects without producing offspring. While biological control agents usually involve no environmental pollutants and are often highly selective, the many complex factors that affect their action sometimes hinder their effectiveness. Other alternative methods are being tested as well. For example, using genetic control, crops can be genetically modified to resist pests and the diseases they cause. Another technique, camo-cropping, involves spraying fabric or non-toxic dye onto growing plants to camouflage them from predators.
US Regulation of Chemical Pesticides
The Insecticide Act of 1910 prohibited the adulteration of insecticides and fungicides. In 1947, the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) authorized the United States Department of Agriculture (USDA) to oversee registration of pesticides and to determine their safety and effectiveness. In December 1970, the newly formed US Environmental Protection Agency (EPA) assumed statutory authority from the USDA over pesticide regulations. Under the Federal Environmental Pesticide Control Act of 1972, an amendment to FIFRA, manufacturers must register all marketed pesticides with the EPA before the product is released. Before registration, the chemicals must undergo exhaustive trials to assess their potential impact on the environment and human health. The EPA’s decision to grant registration is based on the determination that unreasonable adverse effects on human health or the environment are not anticipated within the constraints of approved usage. Beginning in October 1977, the EPA has classified all pesticides to which it has granted registration as either a restricted-usage (to be applied only by certified pest control operators) or unclassified (general-usage) pesticide.
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