David Ragsdale, Ph.D., associate director and chief scientific officer of Texas A&M AgriLife Research, will retire Aug. 31 from an esteemed career in entomology and university administration spanning more than six decades.
Before serving in university administration, Ragsdale served from 2010 to 2019 as head of the Texas A&M Department of Entomology, the largest entomology department in the U.S.
In late August, he was made an honorary lifetime member of the Entomological Society of America for major impacts on entomology through his life’s work in the field.
Ragsdale made far-reaching impacts through his work in the department, including championing early adoption of distance education and shepherding the now nationally accredited bachelor’s degree in forensic and investigative sciences — launched shortly before Ragsdale arrived at Texas A&M University. In addition, enrollment in the department’s graduate program doubled under his direction.
Ragsdale entered his associate directorship with AgriLife Research in 2019. His responsibilities as an agency administrator have included overseeing a research portfolio of nearly $240 million in annual expenditures — encompassing breakthrough discoveries and emerging technology forged by more than 400 doctoral faculty across AgriLife Research.
Early research focus in biological control of plant diseases
Before joining Texas A&M, Ragsdale served as professor, interim department head and director of graduate studies in the University of Minnesota Department of Entomology. He also served as biological control initiative coordinator within the University of Minnesota College of Agriculture, Food and Natural Resource Sciences. From 2003 to 2004, he was the quarantine officer in the state of Minnesota’s high security containment facility.
Between 1994 and 2010, Ragsdale focused his research on solutions for insect vectors of plant pathogens. His early work hinged on efforts to understand the disease dynamics that plagued seed potato producers across the Northern Great Plains. More than 20 years of his research culminated in a 2002 publication outlining the role of aphids in disease transmission and development of a planting scheme that helped reduce spread of aphid transmitted viruses.
“We encouraged producers to hide their early-generation seed potato crops inside another crop field, co-culture,” Ragsdale said. “By not leaving bare ground next to seed potatoes, aphids could not find these potatoes, and this simple cultural technique reduced virus spread by 70%.”
The publication spurred a review article by the Potato Association of America and has been cited 238 times, according to Google Scholar. The research to date has led to new laws in at least seven states, Ragsdale said. It is based on fundamental principles of integrated pest management, IPM, which aims to use sound biological solutions in place of insecticide.
“Insecticides are still needed, but they are a tool for when other tactics fail,” Ragsdale said.
Addressing invasive insect, plant species
When the soybean aphid invaded the upper Midwest, it created immediate yield losses approaching 50%. Ragsdale’s team quickly established an economic threshold — advising producers on the loss point at which to spray pesticides to prevent future yield losses. Agricultural economists at Michigan State University estimated the threshold and the widespread adoption saved soybean producers $1.3 billion over the past 15 years.
At the same time, Ragsdale’s team joined an international group of scientists from academia and the U.S. Department of Agriculture to identify natural enemies of the soybean aphid. They were instrumental in releasing natural parasites, which have decreased soybean aphid numbers in parts of the U.S. Work on this initiative remains ongoing.
In the realm of invasive plant species, Ragsdale was instrumental in introducing two types of leaf beetle to control purple loosestrife. The perennial wet-soil plant outcompeted native plants in the Midwest, creating a monoculture while decimating the habitats of native birds and other wetland animals. Meanwhile, the leaf beetles could not survive on any plant tested by the researchers, except for the purple loosestrife, creating a desirable condition for using the beetles to control this invasive plant.
Ragsdale’s team contributed to a beetle-rearing program that engaged youth groups like 4-H, Boy Scouts of America, Girl Scouts of the U.S.A., K-12 projects and others.
“In about 10 years we had every known wetland in the state of Minnesota that was infested with purple loosestrife colonized by these beetles,” Ragsdale said, “and many sites had native species returning a few years after releasing the beetles.”
Today, the state no longer spends human labor or uses herbicides to manage purple loosestrife.
Impact and accolade
Major milestones of Ragsdale’s career include 106 peer reviewed articles and book chapters, appointments to more than 40 national and academic activities and committees, and more than $16.8 million in grant funding since 1980.
He has received numerous accolades for his field contributions. They include the National Potato Council’s Meritorious Service Award; the Minnesota Soybean Research and Promotion Council’s certificate of appreciation for research and technology transfer; the Potato Association of America’s Outstanding Paper Award for best paper, published in the American Journal of Potato Research; the Minnesota Invasive Species Council’s Carol Mortensen Invasive Species Management Award; the USDA National Award of Excellence in Research; the International IPM Symposium’s International IPM Award of Excellence to the North Central Soybean Entomology Research and Extension Team; and many others.