Agricultural Sciences

Plant pathologist Donald Davis retiring from Penn State after more than 50 years

Donald Davis was a professor of plant pathology and environmental microbiology in Penn State’s College of Agricultural Sciences. Credit: Penn StateCreative Commons

UNIVERSITY PARK, Pa. — Donald Davis, professor of plant pathology and environmental microbiology, is retiring after a career spanning more than 50 years in Penn State’s College of Agricultural Sciences.

Throughout his time at the University, Davis — who has a joint appointment with the Institutes of Energy and the Environment at Penn State — conducted research on tree diseases and biocontrol, including the use of a native fungus to control Ailanthus, or “tree of heaven,” a highly invasive tree species in the Northeastern and mid-Atlantic states.

Additionally, Davis organized and taught two new courses in the Department of Plant Pathology and Environmental Microbiology: Environmental Plant Pathology and Plant Disease Diagnosis. He also co-taught a one-week course in Costa Rica dealing with diseases of neotropical plants.

Carolee Bull, head of the department and professor of plant pathology and systematic bacteriology, noted Davis' collaborative work documenting the ecological impacts and mechanisms of ozone damage on various plant species of natural habitats.

For example, he and his collaborators published the most extensive study of ozone injury on hybrid poplar trees in Pennsylvania with data from a 26-year period. That data has been relied upon by state and federal regulators.

“Professor Davis’ impact on the environment through his work on ozone mitigation and biological control of invasive species, along with his dedication to teaching, have benefited generations of Pennsylvanians,” Bull said.

According to Davis, his childhood spent roaming the local hills and streams near where he grew up in Titusville contributed to an interest in nature that kick-started his career.

Based on the influence of these early experiences, Davis enrolled in the Penn State School of Forestry at Mont Alto and graduated with a bachelor’s degree in forestry in 1964 from Penn State. Two years later, he went on to complete a master’s degree in forestry/silviculture at the University, in which he studied the influence of different soil factors on the growth of black cherry trees in northwestern Pennsylvania.

Davis continued his graduate studies at Penn State in the Department of Plant Pathology, where he was awarded a four-year U.S. Public Health Service predoctoral fellowship. For his doctoral project, he studied the influence of environmental factors on tree species’ response to tropospheric ozone, a newly discovered air pollutant at the time.

Following graduation, Davis worked for the U.S. Forest Service as a forest pathologist in Louisiana and North Carolina, where he became familiar with diseases of southern forests.

“I was at the U.S. Forest Service for almost two years when I saw an opportunity had opened up at Penn State,” Davis said. “I decided to return to my alma mater as an assistant professor of plant pathology extension in the Department of Plant Pathology before transferring to a teaching and research position in the same department, a position that I held for the rest of my career here at the University.”

Davis’ early environmental research programs involved studying how air pollutants, such as ozone and sulfur dioxide, affected both overstory and understory forest species. Based on his research, he evaluated and recommended many potential bioindicator plant species that were useful in illustrating the adverse effects of air pollutants on forest plant species.

Davis received two prestigious Fulbright Awards to continue his ozone research internationally. One award enabled him to study the effects of ozone on plants with colleagues in Wageningen, the Netherlands. The second involved a field study to evaluate the effects of ozone on plants within the Sydney Air Basin, New South Wales, Australia.

Eventually, Davis’s research — comprising more than 150 technical papers funded by such agencies as the U.S. Environmental Protection Agency and the Pennsylvania Department of Environmental Protection — went on to include developing “environmentally green” ways to control artillery fungus, a horticultural pest in landscape mulch.

Eva Pell, senior vice president, dean of the Graduate School, and professor of plant pathology emerita at Penn State, said she first met Davis when he helped escort her around campus during her job interview at Penn State 50 years ago, noting that he remained a close colleague for many years.

“What I learned about Don during the many years we worked together in the department was underscored by those early impressions,” Pell said. “Don was a true field guy — he loved our trips to power plants to look for air pollution damage on vegetation and was a superb diagnostician. Don was the most committed of teachers and his greatest joy was sharing with students his eye for diagnostic detail and his love of the environment.”

Throughout his time as a professor, Davis trained multiple generations of students in forest pathology.

According to colleagues, students who took the course PPEM 318: Diseases of Forest and Shade Trees often raved about Davis as an instructor, and his graduate mentees were loyal supporters and collaborators years after they left Penn State.

Matt Kasson, associate professor of forest pathology at West Virginia University, who was a doctoral student advised by Davis, said he often thinks back to his time with Davis during the early days of their tree of heaven biocontrol research.

“Like so many things he did back then — and really throughout his career — he never centered himself or his contributions to our field,” Kasson said. “He was more focused on listening and learning from others, and in doing so he taught me to lead with humility.”

Last Updated August 12, 2022