History of Pests and Their Management
July 19, 2018 Pests, defined as an insects and other organisms that threaten crops, livestock, pets and people, have threatened civilization throughout history, necessitated the use of chemicals for pest control, and caused the need for the awareness of their potential environmental impacts. This awareness has influenced an evolution toward a more integrated pest management approach that includes the use of pesticides. Diseases of humans and agricultural crops spread by pests have made significant, and often negative, impacts upon society. The need to manage them with chemicals and other controls shows the importance of pest management systems in society. The first section of this document reviews situations when pests caused significant impact in society including death, famine, economic loss and new discoveries and management strategies. Next, historical pest control methods will be discussed. Finally, integrated pest management will be examined.
SIGNIFICANT PESTS IN HISTORY
The Plague, also known as the bubonic or black plague, is one of the most devastating diseases in human history. The disease is caused by the bacterium Yersinia pestis and transmitted between animals and humans by contact with infected fleas, whether it is by bites, direct contact with infected bodily fluids and contaminated materials, or inhalation of infected respiratory droplets. The Plague resulted in the death of about 1/3 of the European population in the early 14th Century, when human’s homes and places of work were inhabited by flea-infested rats. The disease had a profound effect on the course of European history through a creation of a series of religious, social and economic upheavals. The disease was believed to be delivered to the people due to the displeasure of God or by supernatural powers. Numerous references in art, literature and monuments attest to the horrors and devastation of the plague epidemics. Today, science has proven the true cause of the disease, but the fear of suspected plague outbreaks continues. When compared to other diseases caused by other agents, human plague infections are very low, yet the plague still invokes a fear disproportionate to its transmission potential in the post-antibiotic era.
Today, modern antibiotics are effective against the plague; however, if not diagnosed and treated properly, the disease will cause illness or death. People infected with the bacterium often develop symptoms of the disease within one to seven days. Two main clinical forms of plague infections can occur: Pneumonic or bubonic. The most common is the bubonic plague and is characterized by painful, swollen lymph nodes. Plague can be a very severe disease in people, with a case-fatality ratio of 30% to 60% for the bubonic type. The pneumonic kind is always fatal when left untreated. Plague is a serious disease in humans, with a case-fatality ratio of 30% to 60% for the bubonic type, and if left untreated, is always fatal for the pneumonic type. The pneumonic type is especially contagious and can trigger sever epidemics through person-to-person contact via droplets in the air. Luckily, antibiotic treatment is effective against the bacteria causing the plague, so early diagnosis and treatment is important. According to the World Health Organization, from 2010 to 2015 there were 3,248 cases of the plague reported worldwide, including 584 deaths. The three most affected countries are the Democratic Republic of the Congo, Madagascar, and Peru.
Potato Blight
One of the most devastating and historically significant plant diseases is potato late blight. Epidemics of late blight destroyed the potato crops in Europe in the 1840s leading to mass starvation. One of the most significant effects of the disease on the population of the U.S. was the Great Irish Potato Famine from 1845 to 1847, where up to one million people died from the loss of their staple food crop, and nearly the same number of people emigrated to the rest of Europe and the U.S. to prevent starvation and death. Several factors contributed to the starvation, including the land-tenure system in Ireland at the time and the near total dependence of potato as food source for the poorer working population. Late blight is caused by an oomycete or fungus-like microorganism, Phytophthora infestans, which is a specialized pathogen of potato, tomato and other members of the solanaceous plant family. However, for many centuries, the causes of crop failures were a mystery, even for the 19th Century’s potato famine in Ireland. Scientific explorations of potato late blight led to the discovery that plant diseases were caused by microorganisms. This led to the birth of plant pathology as a science. Late blight continues to be a major pest of potatoes, but the disease is managed through the uses of resistant potato cultivars, proper sanitation practices and fungicides.
Fungicides are important in late blight management, particularly in the humid areas favorable for disease development. Contact fungicides are effective and have not resulted in pathogen resistance even after many years of use. These types of fungicides coat the leaves to prevent infection but have no efficacy on controlling the infections once they occur. Systemic fungicides are taken up by the plant and offer post-infection control.
Of special concern are the newly introduced strains of P. infestans because of their resistance to metalaxyl/mefenoxam. In the early 1990s, epidemics of late blight caused some growers in the U.S. to lose their entire potato crops. Special emergency permits were awarded for the use of fungicides not yet registered in the U.S. but available in Europe and beyond. Some new systemic fungicides, such as dimethomorph and cymoxanil were recently registered for potato late blight control. Growers have been encouraged to concentrate on preventative, contact fungicide applications. Some growers routinely use contact fungicide early in the season, while relying on forecasting systems after plants are more mature with a canopy establishment. Still today, the late blight pathogen is one of the major pathogens that chemical companies target in their search for new fungicides.
Downy Mildew of Grapes
Downy mildew is a common and serious disease of grapes that is partly responsible for the introduction of today’s widely used fungicides. This highly destructive disease of grapevines is caused by the oomycete, or water mold, Plasmopara viticola and is a serious disease in all grape-growing areas of the world where there is spring and summer rainfall. It can be traced back to the 1850s in the Bordeaux region of France, where a vineyard producer was having problems with thieves pilfering from his vines. In hopes of making the grapes unattractive to the thieves, he applied a mixture of copper and lime to parts of his vineyard. Not only did it deter the thieves, it deterred the downy mildew disease incidence. This copper-lime mixture came to be known as the Bordeaux Mixture, a commonly used fungicide that is still used today. This discovery was the beginning of modern fungicide use.
Reductions in vine growth, yield, fruit quality and winter hardiness are all symptoms of grape downy mildew. Vine quality can be severely affected with only 3% of fruit infection. The appearance of the fungus is as tiny red flecks in the upper surface of the leaves, later leading to white/gray patches of fungal growth on the leaves and berry skin. Infection is usually sparser on young shoots and leaves, with the most obvious symptom being a gray or purplish discoloration when viewed from a distance. Affected blossom clusters will cause fruit set to be reduced, and because downy mildew attacks all green tissue, the cluster stems are often attacked resulting in berry drop. As the season progresses, infected fruit are often covered in white, powdery growth or misshapen with brown spots on the surface.
Grape Phylloxera
Phylloxera is a serious insect pest of commercial grape production worldwide. The tiny aphid-like insect forms galls on leaves and roots of grapevines. The insect is believed to have originated from the Eastern U.S., where damage from the pest is most prevalent on the leaves of French-American hybrid grapevines. Premature defoliation and reduced shoot growth, yield, and quality of the crop are damage symptoms left by high populations of the insect pest. However, the major damage caused by this insect is due to root infestation. In Europe, phylloxera has great economic importance and has led to research and development programs for genetic resistance as a pest management tactic. European grape varieties should be grafted on American or hybrid grape root stocks. The leaf form of phylloxera doesn’t cause much damage to the vine, so foliar insecticide sprays are of little value to control phylloxera during their wandering stage and are of limited value.
Malaria and Yellow Fever
Mosquitos are responsible for the most common and deadly parasitic disease in the world: Malaria. Malaria is an ancient disease; however, environmental disturbance, malnutrition and the failure of drugs once used to control the disease have conspired to make malaria as serious a problem today as it was during the first half of the 20th Century. Each year, 300 to 500 million cases of malaria will occur, affecting 6 to 9% of the total population. People infected with the malaria parasite often experience fever, chills, and flu-like symptoms. Left untreated, people may develop severe complications and eventually die. One to 3% of the affected will die. For those who survive, the disease normally lasts 10 to 20 days. More than 90% of all cases of malaria occur in Africa. In fact, it is estimated that one child dies from malaria every 30 seconds in Africa. Due to the widespread illness and death it causes, the disease is a great drain on many national economies. Because many malaria-stricken countries are also poor, the disease maintains a vicious cycle of disease and poverty.
The Panama Canal is a major shipping canal that transverses the Isthmus of Panama in Central America, connecting the Atlantic and Pacific Oceans. This canal has had an enormous impact on shipping, significantly cutting travel time down. The canal made it possible to avoid the long and treacherous route via the Drake passage and Cape Horn on the southernmost tip of South America. For example, a ship sailing from New York to San Francisco via the canal cuts its distance by 8,000 miles. However, construction of the Panama Canal was one of the largest and most difficult engineering projects ever undertaken. The construction of the 48-mile canal was plagued by problems, including mosquito-borne diseases such as malaria and yellow fever. It is estimated that more than 27,500 workers died during construction of the canal. The concept of the canal dates back to the early 16th century, and the first attempts to construct the canal started in 1880 under French leadership. Attempts failed until the U.S. completed the canal, and it opened for use in 1914. Since its opening, however, the canal has been tremendously useful, and continues to be a key conduit for international shipping. The canal accommodates the passage of more than 14,000 ships annually, carrying more than 203 million tons of cargo. By 2002, nearly 800,000 ships have passed through the Panama Canal.
Typhoid Fever
Typhoid fever is an illness caused by a bacterium that is transmitted by flies that feed on feces and then on food being prepared for consumption. The disease is most often transmitted through poor hygiene habits and public sanitation conditions. One of the most important components of controlling the spread of typhoid fever is public education campaigns encouraging people to wash their hands after going to the toilet, especially before handling food. To complicate the situation further, a person can be an asymptomatic carrier of the disease, capable of infecting others. According to the Centers for Disease Control, approximately 5% of people who contract typhoid fever continue to carry the disease after they recover. The most notorious carrier of typhoid fever, yet not the most destructive, was Mary Mallon, or “Typhoid Mary,” a cook in New York at the beginning of the 20th Century. In 1907, she became the first identified and traced carrier of the disease. Typhoid Mary was the confirmed source of fifty cases of the disease and five deaths, but it is believed she was the source of infection for several hundred people. Public health officials gave Mary the ultimatum to give up working as a cook or have her gall bladder removed. Mary obliged and quit her job as a cook, just to return later under a false name. Typhoid Mary died of a stroke after 23 years in quarantine.
Cotton Boll Weevil
The boll weevil, Anthonomus grandis, is a beetle that feeds on cotton buds and flowers. It is one of the most important invasive species in agricultural production. The pest migrated into the U.S. from Mexico in 1892, and by the 1920s, the pest had infested all cotton growing areas. This devastated the industry and the people working in the industry in the American South, as well as in South America. The boll weevil has caused an estimated $14 billion in yield losses to the U.S. cotton industry since its arrival in the late 19th century. This insect led to many programs to eradicate boll weevils in several cotton producing states. The boll weevil is also mainly responsible for the inception of the Land Grant University Integrated Pest Management (IPM) programs.
During early years of the weevil’s presence, growers used early-ripening cultivars to try and manage the pest pressure. Following World War II, the development of new pesticides such as DDT enabled farmers in the US to once again grow cotton profitably. Initially, DDT was extremely effective, but pest populations developed resistance to the chemical by the 1950s. Insecticides such as methyl parathion, malathion, and pyrethroids were subsequently used, but environmental and resistance concerns arose as they had with DDT, leaving cotton growers with no practical management strategies. Controlling the boll weevil with insecticides was costly, and the goal of many cotton entomologists was eradication of the boll weevil from US cotton. Area-wide programs began in the 1980s and were cooperative efforts among growers, land grant universities, and the United States Department of Agriculture. The program was successful in eradication of the best from most all cotton growing states. The program has paid off for cotton growers from savings in reduced pesticide costs. The boll weevil eradication program is one of the largest, most successful insect control programs in history.
Predatory Ants in Chinese citrus
In 600 AD, the Chinese were responsible for the earliest use of biological control. The established colonies of predatory ants in citrus for control of destructive pests. Colonies of predatory ants were established in citrus groves using bamboo bridges to facilitate the movement of these beneficial insects between trees to control caterpillar and beetle pests.
PEST CONTROL IN HISTORY
Since the beginning of time, pest control has been vital to the health and longevity of human existence. Records of natural pest control date back to 2500 BC, thousands of years after the beginning of agriculture began in the Fertile Crescent of Mesopotamia. Sulfur, also known as brimstone, was the earliest documented substance used as a pesticide. Its first known use was by pagan priests who used it as medicines, fumigants, bleaching agents and incense in religious rights. The Romans used sulfur, from the fumes from combustion, as an insecticide, to purify a sick room, and to clean the air from evil. In 1000 BC, the same uses of sulfur were reported by Homer in the Odyssey. Today, there are more than 50 sulfur products registered for use as pesticides in Florida alone, primarily used for arthropod control in a wide variety of crops.
As times advanced, experimentation, and sometimes good fortune, led to the discovery of other chemicals with pesticidal activity. For example, early insecticides were plant-derived and included nicotine to control aphids, hellebore to control body lice, and pyrethrins to control a wide variety of insect pests.
By the 1800s, the world was in a time of significant pesticidal discovery period. Substances such as Paris green were being used as an insecticide to control the highly destructive Colorado potato beetle, while the aforementioned copper-lime mixture was used to control grape diseases in France. Compounds such as lead arsenate were being used as an insecticidal orchard spray and gypsy moth control in Massachusetts, while hydrogen cyanide was being used a fumigant in citrus groves in California. In 1873, DDT was first synthesized in the laboratory. In addition, advancements in application efficiencies were occurring. John Bean, a California almond farmer, invented a pressure sprayer that led to more efficient applications in crops. In the later part of the century, steam, mechanical and horse driven pesticide spray equipment was developed. By the 1900s, the first pesticide legislation, the Federal Insecticide Act (FIA) was enacted to protect farmers and consumers from fraudulent manufacturers, setting standards to ensure quality pesticides were produced.
Up until the 1940s, chemicals derived from plants and inorganic compounds were the source of pest control. During World War II, the synthetic compound DDT played a significant role in saving Allied soldiers from insect transmitted diseases and subsequently was hailed as the insecticide to solve all insect issues. At this time, synthetic pesticide production increased significantly, and the modern-day chemical industry was launched, thus starting a new era of pest control. The 1940s also saw the introduction of warfarin in rodent control, as well as the availability of German synthesized organophosphate insecticides. Malathion was introduced at a later time in the 1950s and is probably the safest of all the organophosphate insecticides. It continues to play an important role in mosquito control programs and the U.S. government’s eradication programs. Another significant compound synthesized in the post-World War II era was 2,4-Dichlorophenoxyacetic acid, or 2,4-D, the first selective herbicide that killed most broadleaf weeds but not grasses. It’s first uses were reported as a growth regulator and was an effective control agent for dandelion, plantain and various other broadleaf weeds in a bluegrass lawn. It is still one of the most widely available and used herbicides on the market, however the exact mode of action is still not understood.
Significant success coupled with low costs caused pesticides to become the primary source of pest control. These new pesticides provided season-long crop protection against pests as well as complemented the fertilizer benefits and other innovative agricultural production practices. For Florida agriculture, the use of fungicides was very important. Cucumber yields nearly doubled and this increase in yields was attributed to fungal disease control. Also during this time, insecticide aerosol sprays for control of household and indoor pests such as ants and cockroaches entered the market and are now found in practically every household. This new-found success of pest control with modern synthetics, particularly in agriculture and public health, encouraged widespread acceptance and eventual reliance upon them.
A biological insecticide, Bacillus thuringiensis (Bt), hit the market in 1960 for insect control in lettuce and cole crops. Bt is a bacterium that is pathogenic to the larvae of some pests, especially lepidopterous pests. The bacterium contains endotoxins that can paralyze and lyse the insect gut causing mortality through starvation. Several generations of Bt products have evolved since its introduction of the first.
In recent years, the disadvantages of the heavy dependence of pesticides have surfaced. Development of pesticide resistance is one of the most significant disadvantages of their widespread use. The first resistance found was in 1908 and was a case of San Jose scales resistant to lime sulfur compounds. Since then, hundreds of insect pests have become resistant to one or more pesticides worldwide. Only a few years after the introduction of DDT, resistance was confirmed in houseflies in Sweden. Within 20 years, more than 224 other insect species were reported resistance to synthetic pesticides. Every class of insecticides has had resistance issues emerge. Today, more than 500 insects, 300 weed biotypes and numerous plant pathogens have developed pesticide resistance.
Environmental and human health concerns also became significant challenges to pesticide use. Although the Federal Insecticide Act of 1910 set standards for chemical quality and provided consumers protection, it failed to address the potential damage to the environment and human health risks associated with such widespread use of insecticides. In order to address some of those shortcomings, Congress passed the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) in 1947.
In 1962, Rachel Carson published “Silent Spring,” a book that examined pesticides and their effects on the environment. Her primary concern was with DDT and other chlorinated hydrocarbons, because of their stability and persistence in the environment. A major contributing factor to DDT’s effectiveness was its long residual activity, but this persistence contributed to bioaccumulation, or their ability to accumulate in the fatty tissues of animals. It was found in some situations that the biomagnification of insecticides occurred. This is when organisms, such as birds of prey, accumulate chemical residues in higher concentrations than those found in the organisms they consume. The U.S. has experienced a level of unprecedented environmental awareness since the publication of Carson’s “Silent Spring.”
Mandated by Congress, the U.S. Environmental Protection Agency (EPA) was created in 1970. The task of the EPA was and remains today, to implement by regulation the laws passed by Congress in order to protect the environment and the health of humans and other animals. In 1972, EPA banned DDT use in the United States, and further regulatory action has been taken against many other pesticides thought to pose significant environmental and health hazards. Public concern has paved the way to more stringent regulation of pesticides and changes in the types of pesticides produced.
In 1972, Congress enacted significant revision to FIFRA with the Federal Environmental Pesticide Control Act. This amendment transferred regulatory responsibility to the EPA and changed the emphasis of the law to protect the environment and public health. In 1988, Congress amended registration provision and required re-registration of many pesticides that had been registered before 1984. Again, the act was amended in 1996 by the Food Quality Protection Act and the Pesticide Registration Improvement Extension Act of 2012.
The following presents a chronological list of significant pesticide events in history:
A Chronological List of Selected Significant Events Involving Pesticides
*Source: F. Fishel, UF/IFAS Extension PI-219
• 12,000 BC: First records of insects in human society.
• 2,000 BC: First reported use of sulfur as a pesticide by pre-Roman civilizations.
• 1,200 BC: First reports of nonselective herbicide use as biblical armies salt and ash the fields of the conquered.
• 100 BC: The Romans apply hellebore for control of rats, mice, and insects.
• 300: Earliest recording of biological control – Chinese use predatory ants in citrus for control of destructive insects.
• 900: Chinese use arsenic to control garden insects.
• 1649: Rotenone used to paralyze fish in South America.
• 1690: Nicotine extracted from tobacco for insecticide use.
• 1787: Soap mentioned as an insecticide.
• 1848: Rotenone used as an insecticide in Asia.
• 1850s: Lime and copper mixture used for plant disease control on grape in France.
• 1860s: Paris green, an arsenical, used as an insecticide for control of Colorado potato beetle.
• 1873: DDT first made in the laboratory.
• 1882: Bordeaux mixture discovered in France for control of plant diseases.
• 1883: John Bean invents pressure sprayer for pesticide application leading to efficient applications to crops.
• 1886: Hydrogen cyanide fumigant use in California citrus.
• 1892: Lead arsenate discovered for gypsy moth control in Massachusetts.
• 1894–1900: Steam-, mechanical-, and horse-driven pesticide spray equipment developed.
• 1907–1911: Industry begins production of lead arsenate.
• 1910: Passage of Federal Insecticide Act (precursor to today’s Federal Insecticide, Fungicide, and Rodenticide Act).
• 1921: First use of airplane to apply a pesticide.
• 1927: Tolerance established for arsenic on apples by U.S. Food and Drug Administration.
• 1932: Methyl bromide first used as a fumigant in France.
• 1932–1939: Insecticidal properties of DDT studied and described in Switzerland.
• 1936: Pentachlorophenol introduced as a wood preservative.
• 1942: DDT made available for U.S. military use (civilian use available in 1945).
• 1942: Herbicidal properties of phenoxy acetic acids described, including 2,4-D.
• 1944: Introduction of warfarin for rodent control
• 1946: Organophosphates insecticides, developed in Germany, made available in U.S.
• 1950s–1960s: Massive industrial research, development, and commercialization of multiple classes and families of pesticides.
• 1961: Bacillus thuringiensis first registered.
• 1962: Publication of Silent Spring by Rachel Carson.
• 1965: Atrazine registered as an herbicide.
• 1970: Formation of the U.S. Environmental Protection Agency (responsible for pesticide registration).
• 1971: Herbicidal properties of glyphosate described.
• 1972: DDT uses cancelled by the EPA.
• 1973: Development of first photo-stable synthetic pyrethroid insecticide, permethrin.
• 1978: EPA releases first list of restricted-use pesticides.
• 1980s: EPA cancels many uses of chlorinated hydrocarbon pesticides.
• 1996: Monsanto introduces Roundup Ready soybeans, the first transgenic crop with major market prospects.
• 1996: Food Quality Protection Act becomes law.
• 1990s and 2000s: Mergers and buyouts in the pesticide industry.
INTEGRATED PEST MANAGEMENT
Shortly after World War II, when synthetic insecticides such as DDT became widely available, a concept of “supervised insect control” was being developed by California entomologists in the northwest side of San Joaquin Valley. This type of control was “supervised” by trained entomologists and insecticide applications were based on conclusions made from methodical monitoring of pest and natural enemy populations and proved successful for control of the alfalfa caterpillar, and other pests of alfalfa and cotton.
Supervised control was based on scientific studies of the interrelationships between insect pests and their environment. Using these studies, it was possible to make informed predictions of insect pests and their natural enemies based upon populations. These predictions made it possible to use preventative cultural controls to their fullest extent and to time any necessary chemical controls more effectively. At about the same time, entomologists in the southern U.S. cotton growing regions were advocating a similar approach to insect control.
The idea of supervised control was the basis for “integrated control” that the University of California entomologists articulated in the 1950s. Integrated control aimed to identify the appropriate mixture of chemical and biological controls for a particular insect pest. When chemical controls were necessary, they were chosen in the manner least disruptive to the natural enemies, or biological controls. With this concept, pesticides were only to be applied after regular monitoring the crop indicated the pest population had reached a level, also known as the economic threshold, that required treatment to prevent the population from reaching a higher level where economic losses would exceed the cost of control measures, also known as the economic injury level.
Integrated Pest Management (IPM) took the integrated control concept further to all classes of pest and included multiple tactics of control. IPM is an approach to pest control that focuses on pest prevention by eliminating the underlying causes of the pest problems. One example of IPM is the monitoring of the previously mention cotton boll weevil in Arkansas in 1901. Economic thresholds, which are fundamental to IPM, were used to time pesticide applications of this significant pest.
IPM is a multi-tactical approach as opposed to a single tactic, like pesticide applications. Tactics such as host-plant resistance and cultural manipulations became part of the IPM framework. IPM is a series of pest management evaluations, decisions and controls and follows a four-tiered approach, (1) Set action thresholds, (2) monitor and identify pests correctly, (3) prevent, and (4) control. Pesticide applications are used when all other control efforts have failed, and pesticides with the least potential harm to the humans, animals and the environment are employed.
REFERENCES
• Pest Management and Pesticides: A Historical Perspective. 2016. Frederick M. Fishel. UF/IFAS Extension PI-219.
• Plague. 2017. World Health Organization Fact Sheet.
• Late Blight on Potato and Tomato. 2016. Pamela Roberts and Ryan Donahoo.
• Late Blight of Potato and Tomato. 2005. G.L. Schumann and C. J. D’Arcy. The Plant Health Instructor. DOI: 10.1094/PHI-I-2000-0724-01.
• Malaria. 2018. CDC Fact Sheet.
• Supervised Control of Insects. Ray F. Smith and Gordon Smith. California Agriculture. 1949.