Site of Animal Health Discovery
Kerrville, Kerr County, Texas
Marker Inscription
In this building (at Menard) during late 1930s, Dr. Edward F. Knipling (b. 1909) advanced theory screwworms might be eradicated by releasing sterile male flies to break chain of reproduction and save livestock from role of host to parasitic larvae that destroy livestock and wildlife. During 1950-51, this laboratory (removed to Kerrville area) was site of sterilization of male screwworms with irradiation, in procedures by Dr. R. C. Bushland and D. E. Hopkins. The outcome: eradication of the screwworm and saving of domestic and wild animals of the United States. (1972)
Erected by Texas Historical Commission
The Story
In the late 1930s Dr. Edward F. Knipling advanced a daring idea: that the screwworm, a parasite whose larvae destroyed livestock and wildlife, might be wiped out by releasing sterilized male flies to break its chain of reproduction. In 1950–51, at a laboratory moved to the Kerrville area, Dr. R. C. Bushland and D. E. Hopkins sterilized male screwworms using irradiation. The technique worked, leading to the eradication of the screwworm and saving countless domestic and wild animals across the United States.
Why it matters
The "sterile insect technique" pioneered here became a landmark of American agricultural science, showing how basic research could solve a scourge that plagued ranchers for generations.
The story behind this marker
AI contextThe era
For generations, ranchers across the American South and Southwest dreaded the screwworm. The adult fly lays its eggs in open wounds on animals, even something as small as a scratch or a newborn calf's navel. The larvae then feed on living flesh. Untreated infestations could kill cattle, sheep, goats, and wild animals like deer. Fighting it meant endless riding, doctoring, and loss.
In the 1930s, American agriculture was reeling from drought and depression, and federal scientists were searching for ways to protect livestock. Most pest control of the era meant poisons and constant treatment. That work was expensive and never finished, because the flies always came back.
The breakthrough began at a modest government laboratory in Menard, Texas, in the Hill Country ranching region. That is where the story on this marker starts, before the laboratory was moved to the Kerrville area, where the work continued.
People & events
In the late 1930s, a young entomologist named Edward F. Knipling proposed a startlingly unconventional idea. The females of this species were understood to mate only once. If huge numbers of sterile males were released into the wild, many females would mate with them and lay eggs that never hatched. Release enough sterile flies for enough generations, and the population would collapse on its own.
The theory needed a practical way to sterilize flies without ruining them, and that took years. In 1950–51, at the laboratory by then relocated to the Kerrville area, Dr. R. C. Bushland and D. E. Hopkins worked out procedures for sterilizing male screwworms with irradiation. The treated flies could still compete for mates but could no longer produce offspring. The idea was now a tool.
The method went on to be proven in the field. It was first tested on the Caribbean island of Curaçao in the 1950s and then used in a large program in the southeastern United States. Knipling and Bushland were later honored internationally for the work, and deservedly so. It began as a thought experiment in a small Texas lab and ended as one of the great practical victories in the history of agricultural science.
Its place in the American story
What was pioneered here became known as the sterile insect technique, and its reach went far beyond Texas. Eradicating the screwworm from the United States saved ranchers enormous losses and spared countless deer and other wildlife. The same approach was later adapted to fight other pests around the world, including fruit flies that threaten crops.
The story is also an example of how patient, publicly funded research can solve a problem that brute force never could. Instead of poisoning the landscape, scientists used the insect's own biology against it. That was a remarkably targeted solution for its time.
The victory has had to be defended ever since. The screwworm still lives in parts of the Americas, and it has reappeared at times, so sterile-fly releases remain the front-line defense. The idea born in these Hill Country labs is still doing its job decades later.
If you visit
There's no dramatic battlefield or grand house here. This marker commemorates an idea and the careful laboratory work that made it real. Take a moment to picture the ranch country around you as it was before the 1950s, when every calving season and every barbed-wire cut carried the threat of infestation.
Kerrville is a gateway to the Texas Hill Country, with the Guadalupe River, winding scenic roads, and working ranchland all around. That setting is the point. This is exactly the kind of landscape the research was meant to protect, and many of the ranch families here remember the screwworm days through their elders' stories.
If you're traveling west through the Hill Country, it's worth continuing on to Menard, where Knipling first developed his theory. Seeing both places shows you how a scientific revolution can grow quietly in small towns far from any university campus.
Written by AI to add context, grounded in the marker’s inscription and the historical record. The inscription above is the original, unaltered text.
Own a business near here? Add it to the map.
Related people
- · Edward F. Knipling
- · R. C. Bushland
Themes & tags
Nearby & related markers
Beitel Lumberyard
Kerrville, TX
When the San Antonio & Aransas Pass Railroad made Kerrville its last stop, San Antonio lumberman Frank J. Beitel bought land here in 1889 to open a lumberyard, betting on the county's timber and coming growth. The business thrived, expanding into a warehouse, retail building, and lumber shed, and gained its own rail spur for loading goods after the town's depot was rebuilt in the 1910s. For more than a century the yard supplied the materials that built Kerrville.
Kerrville Daily Times
Kerrville, TX
The Kerrville Daily Times traces its lineage to the Center Point News, founded in 1910 and moved to Kerrville in 1925 by James J. Starkey, son of Kerr County pioneers. Starkey renamed it more than once—settling on The Kerrville Times—while writing a "Pioneer History" column until his death. His nephew G. Rankin Starkey and co-publisher Sam Braswell converted it to a daily in 1949, and over the decades it absorbed rival papers to become the Hill Country's only daily. It remains one of the oldest continuously operating businesses in the county.
H-E-B
Kerrville, TX
In 1905 Florence Butt invested $60 to open the C. C. Butt Grocery Store on Main Street in Kerrville, living with her family above the shop. Her youngest son, Howard E. Butt, delivered groceries as a boy and, after returning from World War I, transformed the business with a cash-and-carry model and expansion into the Rio Grande Valley. From those hill-country beginnings grew H-E-B, today one of the largest privately held companies in the United States and the biggest private employer in Texas.
The Comparette Home
Kerrville, TX
Built in 1890 in Kerrville's Tivy Addition, this Victorian house passed through several hands during the Texas Hill Country's Gilded Age growth, including the prominent physician Dr. R. H. P. Wright. It is best known for D. H. Comparette, a civic leader who organized and managed the Kerrville Telephone Company, whose family held the home for more than seventy years. One of Dr. Wright's daughters married future Texas Governor Coke Stevenson, tying the house to the state's political history.