The following biographical sketch of Edward Fred Knipling includes information on the history of the efforts of the U.S. Department of Agriculture, Agricultural Research Service (ARS) and Animal and Plant Health Inspection Service (APHIS) to eradicate the screwworm, a parasite of livestock and other warm-blooded animals. Because Knipling's role in this eradication program was critical to its success, extensive information on the program is included in this biographical sketch.
Edward Fred Knipling (1909-2000) was a world-famous entomologist and theorist. He advocated the use of pest specific, preventive, and environmentally-safe methods applied on an area-wide basis. His contributions include the parasitoid augmentation technique, insect control methods involving the medication of the hosts, and various models of total insect population management. Knipling was best known as the inventor of the sterile insect technique (SIT), an autocidal theory of total insect population management. SIT controls insect populations by releasing sexually sterile males which leads to a reduced birth rate. The New York Times Magazine proclaimed on January 11, 1970, that "Knipling...has been credited by some scientists as having come up with 'the single most original thought in the 20th century.'"
Knipling, or "Knip", was born on March 20, 1909, in Port Lavaca, Texas. He was the ninth of 10 children born to Henry John Knipling and Hulda Rasch Knipling. While growing up in a German-speaking Lutheran household, Knipling worked on his father's farm from childhood through college. Knipling graduated from Port Lavaca High School at the age of 17. He studied agriculture and entomology at the Agricultural and Mechanical College of Texas (now Texas A&M University). After his graduation in 1930, he continued his studies in entomology at Iowa State College (now University), where he was awarded a master of science degree two years later. Knipling later earned his doctorate from Iowa State College in 1947.
In the summer of 1934, Edward married Phoebe Rebecca Hall, whom he met while studying at Iowa State. Phoebe Knipling was a well-established scholar who at the age of 19 earned a bachelor of science degree from Catawba College in 1929. By the age of 23, she had earned master of science and doctor of philosophy degrees in parasitology and protozoology from Iowa State. Phoebe Knipling later served as the first Science Supervisor for the Arlington, Virginia, public school system. The Kniplings had five children: Anita, Edward, Edwina, Gary, and Ronald.
Knipling spent his entire career with the U.S. Department of Agriculture (USDA), beginning with a temporary summer job in 1930; the USDA employed him for 41 years and then provided him with collaborator status for 3 additional decades. Knipling steadily rose through the ranks and held the following three very significant positions: (1) Director of the Orlando Laboratory (1942-1946) on Emergency Research to protect U.S. and Allied armed forces from the disease-carrying insects that spread malaria, typhus, and plague; (2) Director of the USDA's nation-wide research on insects affecting livestock, man, households, and stored products from headquarters at Washington, D.C. (1946-1953); and (3) Director of the Entomology Research Division (ERD), Agricultural Research Service (ARS), headquartered at the Beltsville Agricultural Research Center, Beltsville, Maryland (1953-1971).
Working as a field aid in Tlahualilo, Mexico, he studied the pink bollworm (Pectinophora gossypiella). The following summer he was appointed junior entomologist at the Dallas, Texas, laboratory of the Bureau of Entomology and Plant Quarantine (BEPQ). In Dallas, he examined the biology and control of the screwworm (Cochliomyia hominivorax). From 1932 to 1935 Knipling worked in Illinois and Iowa researching cattle grubs, horn flies, and the common horse bot. In 1935, the USDA opened a new laboratory in Valdosta, Georgia, with Ernest William Laake in charge, and Knipling and Walter E. Dove as assistant entomologists. It was the mission of the staff working in the laboratory to assist the livestock industry in coping with the screwworm. The screwworm had been introduced inadvertently into the southeastern United States on infested cattle shipped from the southern Great Plains to save them from the severe drought of the Dust Bowl era.
Knipling transferred to the Menard, Texas, laboratory of the BEPQ to continue his research. He worked at Menard from 1937 to 1940 conducting research on the screwworm. The staff at Menard included Roy C. Melvin, Henry Edward Parish, and Raymond C. Bushland (with whom he later collaborated on several crucial screwworm projects). The laboratory was charged with developing formulations, or "smears," to treat animals infested with screwworms. The smears served two functions--to kill the screwworms that infested the animal and to seal the wound to reduce the chances of re-infestation. The resulting Smear 62 could accomplish both of these tasks with a single application. Yet, Knipling realized that an effective wound treatment would never fully control the screwworm fly and would always entail high labor costs. According to Knipling, "What we needed was some preventive measure."
While at Menard, Knipling formulated an autocidal method of insect control which involved overwhelming the wild populations with genetically altered or sterile males to either suppress or eradicate the total population in an ecologically isolated region. This controversial method became known as the sterile insect technique (SIT). It had three main components:
- mathematical modeling (conceived by Knipling) that predicts the probability of sterility when an uncontrolled wild population is subjected to releases of sexually sterile insects at an initial over-flooding ratio, which assures a decline in the number of progeny produced in the target population;
- a mechanism for mass rearing the number of insects necessary to overwhelm the natural population (which was developed by Melvin and Bushland); and
- a method for sexually sterilizing the mass-reared insects (which eluded scientists until Hermann Joseph Muller's irradiation studies in 1950).
The development of SIT was put on hold for several years because the needed technology was still unknown at this time. After Menard, Knipling was placed in charge of a station of the Division of Insects Affecting Man and Animals in Portland, Oregon. At this post, he investigated mosquito populations of the Pacific Northwest. The United States then entered World War II and Knipling's work took a new direction.
In 1942, Knipling was called to lead a team of scientists in Orlando, Florida. The staff at Orlando included Raymond C. Bushland and Arthur W. Lindquist (who was also involved with screwworm research in the 1930s). The team's task was to find methods to control insect populations that transmit diseases such as typhus, malaria, and plague to the U.S. and Allied forces. The laboratory received samples of numerous chemicals and materials from all over the world, each of which was tested for its capability to control insect pests. The lab developed a successful louse powder, designated the name MYL, for the troops to use for controlling body lice and similar pests. The next advance came from a sample of dichloro-diphenyl-trichloroethane (DDT) from the J.R. Geigy Company in Switzerland. The lab not only developed DDT into a product that could help the troops, but they also made DDT practical for many other agricultural purposes.
After the war, Knipling returned to Iowa State where he earned his Ph.D. in entomology. In 1946, Emory Clayton Cushing retired from the position of Chief of Insects Affecting Man and Animals Branch and Knipling was chosen to replace him. While in this position, Knipling consolidated all screwworm research at a new Livestock Insects Laboratory in Kerrville, Texas. After the reorganization of the USDA in 1953, Knipling became the Director of the Entomology Research Division (ERD) of the newly created Agricultural Research Service (ARS). In this capacity, he was able to shift the focus of insect control from chemical insecticides to other methods such as biological and parasitoid. This served as a major landmark in the development of ecologically sound alternatives to the mass use of insecticides.
By the early 1950s, the screwworm had become a major concern. Lindquist forwarded to Knipling a reference to an article in the January 1950 issue of American Scientist written by Hermann Joseph Muller, a geneticist who had won the Nobel Prize in Physiology or Medicine in 1946. Muller's "Radiation Damage to the Genetic Material" explains how x-rays could be used on fruit flies for sterilization without negatively affecting sexual behavior or competitiveness in the wild. Muller agreed with Knipling's theory that sterile insect technique (SIT) would be feasible for controlling the screwworm.
Knipling pursued research on sterility by radiation. He turned to Bushland, who had become the director of research at the Kerrville, Texas, laboratory of the ARS. Using Knipling's theory and Muller's technique, Bushland completed a successful experiment. The sterile male flies were able to mate competitively, and the percentage of sterile males in the population was about equal to the percentage of infertile egg masses oviposited by female flies. Bushland later discovered that using gamma rays from cobalt-60 was a less expensive, but effective alternative to x-rays.
The next stage was field experimentation. In late 1951, an experiment was established on Sanibel Island in Florida by Knipling, Bushland, and Alfred H. Baumhover, an entomologist working with Bushland at Kerrville. The experiment proved that it was possible to drastically reduce the screwworm population by releasing sterilized flies. Because the island was only two miles from the mainland, however, the continuing influx of screwworms from the Florida peninsula prevented eradication. The scientists needed a more isolated area.
In 1953, shortly following the Sanibel experiment, Knipling received a letter from Benjamin A. Bitter, a veterinarian on the island of Curacao, Netherlands Antilles, 40 miles off the coast of Venezuela. Bitter was looking for a way to deal with the screwworm problem that had invaded the island from South America. Knipling responded with a proposal for a joint experiment between the United States and the Netherlands. Knipling clearly stipulated that SIT was only a theory, and could not be guaranteed to work. Bitter was interested in the cooperative effort and the team of Knipling, Bushland, Lindquist, Baumhover and Bitter spent nine months planning the experiment. About 150,000 sterile screwworm flies per week were released over Curacao, a small island of 176 square miles; within 3 months and 4 generations of the targeted insect, the screwworm was eradicated from the island.
From the Curacao experiment, the scientists learned how to put together a full-scale eradication program. Components of the experiment included mass rearing of screwworm flies, proper sterilization equipment and procedures, and an efficient aircraft method of dissemination.
Although the Curacao experiment had not initially been well publicized in the United States, its success soon garnered attention from agricultural officials. Most of this interest came from Florida. Through a series of meetings with state and federal officials, Knipling helped secure the initial appropriations to eradicate the screwworm from the Southeastern United States. The Florida eradication program was given a boost when, in December 1957, an unseasonably cold air mass swept through Florida and killed all screwworms southward to a line running from Tampa to Vero Beach, Florida. The USDA took advantage of this situation and began releasing the sterile flies. The program was considered a success when no screwworms could be found in Florida after the end of June 1959.
Livestock producers in the Southwest, especially those in Texas, favorably viewed the Southeast screwworm eradication program. The challenges in Texas were much more difficult than those encountered in Florida. They included an increased area, a larger insect population, less isolation, and the guarantee that flies could easily reinfest the area from outside the program's jurisdiction. To solve the screwworm problem in the Southwest, a fly production plant was constructed in Mission, Texas, and the partnership of the Mexico-USA Screwworm Eradication Commission launched joint operations to maintain a sterile border between the United States and Mexico to reduce the possibility of reinfestation. By 1972, the screwworm had been officially eradicated from the United States.
The screwworm eradication programs are practical examples of the application of Knipling's theories on total insect population management. The programs involved: using field experimentation to gather baseline data on the wild population using this baseline data to develop a model of the likely effects of a SIT program; conducting a pilot project to assess the validity of the model and the readiness of the technology; conducting detailed planning; constructing laboratories and mass rearing facilities; developing methods of handling sterilization and aerial release; and properly using monitoring methods. This area-wide model was considered to be far more effective than the use of chemical insecticides on small populations of insect pests on a case-by-case basis. Knipling further discussed his model in his 1979 book, The Basic Principles of Insect Population Suppression and Management (USDA Agriculture Handbook 512).
The sterile insect technique helped to save billions of dollars for the livestock industries in the United States, Mexico, and Central America at an attractive cost to benefit ratio. This, however, was not the only technique of population control Knipling developed. He considered his work on insect parasites to be as equally important as SIT. He also believed that when combined with SIT, the parasitoid augmentation technique could be more effective for managing insect populations than either one operating alone. Knipling's second book, Principles of Insect Parasitism Analyzed from New Perspectives: Practical Implications for Regulating Insect Populations by Biological Means (USDA Agriculture Handbook 693), published in 1992, contains information on the use of parasites for insect control.
Knipling served as the director of the ERD until 1971, at which time he became the science advisor to George W. Irving, Jr., Administrator of the ARS. Two years later, Knipling retired from the USDA, having served for over 40 years. After retirement, he continued to collaborate with ARS and contribute to the literature of entomology. During this period, he completed about 30 of his more than 200 publications on insects, and many more works that were not published. Knipling remained active in the field of entomology until the weeks prior to his death in March 2000.
Throughout his career, Knipling was honored with fellowships and honorary memberships from such organizations as the Entomological Society of America, the National Academy of Sciences, and the American Academy for the Advancement of Science. Knipling was also the recipient of numerous awards and honors, including several honorary doctor of science degrees. These awards include the British King's Medal for Service in the Cause of Freedom, the Presidential Medal for Merit, the National Medal of Science, an ARS Science Hall of Fame induction, the World Food Prize, and the Japan Prize. ;In 1988, the U.S. Livestock Insects Laboratory in Kerrville, Texas, which was created in 1946 as the merger of the Dallas, Uvalde, and Menard laboratories, was rededicated in honor of Knipling and Bushland.
Special Collections would like to thank Waldemar Klassen for his extensive contributions to this section. Klassen worked closely with Knipling and the USDA's pest management programs throughout his career. He has served as the National Program Leader for Pest Management (ARS, USDA, 1972-1983), director of the Beltsville Agricultural Research Center (ARS, USDA, 1983-1988), associate deputy administrator for Plant Sciences and Natural Resources (ARS, USDA, 1988-1990), before moving on to positions within the Joint FAO/IAEA Division for Nuclear Techniques in Food and Agriculture in Vienna, Austria (1990-1994). Klassen currently serves as the director of the Tropical Research and Education Center at the University of Florida. Materials involving Klassen can be found within this collection in Series I, IV, and VI.
Extended Biographical Sketch (PDF|152KB)
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