High-risk plant pathogens have a new foe

Combining plant pathology and unmanned aircraft to build the groundwork for an early-warning system

Modern-day plant pathology traces its origins to the Irish Potato Famine in the 1840s and 1850s, when scientists began to study a fungus-like organism responsible for the deadly potato blight. Unmanned aircraft, on the other hand, draw upon a history that has only flourished in the last few decades.

David Schmale, assistant professor of plant pathology, physiology, and weed science in the College of Agriculture and Life Sciences, has merged these two disciplines to investigate microbial life in the lower atmosphere. By retrofitting hobby-size airplanes with autonomous systems and spore collection devices that open mid-flight, the Schmale Laboratory has not only shed light on a whole universe of microorganisms above agricultural fields but also laid the groundwork for an early-warning detection system that could mitigate the spread of harmful airborne pathogens.


Autonomous unmanned aerial vehicle Autonomous unmanned aerial vehicles can sample more than 150,000 liters of air during a single flight.

For example, Schmale and his colleagues Elson Shields, professor of entomology at Cornell University; and Donald Aylor, distinguished scientist at The Connecticut Agricultural Experiment Station, have a $1 million grant from the U.S. Department of Agriculture to study how Phytophthora infestans traverses the lower atmosphere. By studying the malignant organism that causes late blight in potatoes and tomatoes, Schmale has come full circle to investigate the very pathogen that sparked the science of plant pathology, his field of study.


David Schmale gives a mushroom demonstration David Schmale displays fungus varieties for students in his Mysterious Mushrooms, Malicious Molds class. In this popular undergraduate course, students learn about the agriculture, food safety, and human health aspects of fungi. During the class, they also form small groups to cultivate edible varieties of mushrooms.

“This research will allow scientists to know where this pathogen could move and what strategies we could use to mitigate it if an epidemic occurs,” said Schmale, who adds that Virginia’s Eastern Shore had an outbreak of the high-risk plant pathogen as recently as 1996. “One outcome of this project will be the development of an online resource that provides growers and producers with rapid forecasting of the potential spread of late blight so they can take appropriate measures to safeguard their crops.”

Because of its applications to agriculture, Schmale's research is conducted with autonomous unmanned aerial vehicles (UAVs) above Virginia Tech’s Kentland Farm, a 1,900-acre research facility near Blacksburg, Va. An affiliate faculty member in the Virginia Center for Autonomous Systems, Schmale applies cutting-edge technology -- typically used for military applications -- to the world of plant pathology.

The autonomous unmanned aerial vehicles have several advantages over remote-controlled aircraft, which scientists have been using to monitor the spread of airborne pathogens for years. “First, autonomous UAVs maintain a very precise sampling path,” Schmale explained. “We can establish a global positioning system waypoint in the center of an agricultural field, and the autonomous plane can circle around that waypoint at a set altitude, with about a meter variation up and down. Second, the autonomous technology enables us to have coordinated flights with multiple aircraft. We can have two aircraft sampling pathogens at the same time but at different altitudes.”

‘Teeming with microbial life’

Through his research, Schmale has confirmed that the lower atmosphere is buzzing with activity.


Microbial community grows in a petri dish. This sampling collection plate holds a microbial community. Typically, antibiotics will be placed on the plates so only one species will grow.

“We know that microbes mediate important biochemical processes in the soil, the ocean, and a variety of extreme environments,” Schmale said. “It is not so far-fetched that a similar drama unfolds in the atmosphere, which we know is teeming with microbial life.”

Schmale began to uncover this theater of life by placing antibiotics in the collection plates of his UAVs to ensure that only samples of the fungal genus Fusarium would grow. Fusarium, which is responsible for some of the world’s most devastating plant and animal diseases, proved to be an interesting case: Schmale collected hundreds of viable colonies of Fusarium representing at least a dozen species, all but one of which scientists had never before observed traveling a significant distance above the earth’s surface.

After these fascinating results, Schmale expanded his interests to include “aerogenomics,” the exploration of entire microbial assemblages in the lower atmosphere. “In many of our samples, we have found organisms that have never been cultured before,” Schmale explained. “Some of these microbes may thrive only in the atmosphere, and many of them may be new to science.”


A spoangium, or fungus-like organism A sporangium of P. infestans is capable of causing the late blight in potatoes and tomatoes. This fungus-like organism caused a famine in 19th-century Ireland that resulted in more than one million deaths.

Schmale hypothesizes that at least some airborne microbes interact with each other as a community of microorganisms in the atmosphere through novel biochemical processes. With the help of the Virginia Bioinformatics Institute, Schmale has brought faculty with expertise in genomics and bioinformatics to the project. He has gained access to powerful sampling equipment such as the institute’s Roche GS-FLX high-throughput sequencing system to test his hypothesis.

This partnership has allowed Schmale and his colleagues to survey the biotic diversity in the lower atmosphere in new and exciting ways. Today, Schmale continues to collect data and investigate further applications of autonomous systems in the field of aerobiology.

From the homepage

    David Schmale with an unmanned aerial vehicle.

A real-time polymerase chain reaction machine allows Schmale to detect and quantify microorganisms within a matter of minutes following sample collection.

Research on autonomous systems

The Virginia Center for Autonomous Systems (VaCAS) facilitates collaboration related to autonomous systems in three colleges at Virginia Tech:

Center faculty members study fundamental control theory, develop autonomous vehicles, and find applications for their research in science, security, and commerce. Schmale and other affiliate faculty members in the College of Agriculture and Life Sciences bring the fields of plant pathology, entomology, and horticulture to the Virginia Center for Autonomous Systems.


  • View a short video that demonstrates the use of autonomous unmanned aerial vehicles to study microbes in the lower atmosphere.
  • Listen to an "Inside Virginia Tech" football radio broadcast about Schmale's research.
    Podcast (MP3 | 937KB)

Bringing fungi into the classroom


Mushrooms There are an estimated 1.5 million species of fungus, but scientists have only described about 75,000 of them.

The U.S. Department of Agriculture grant to research P. infestans includes funding for a new undergraduate course in the Department of Plant Pathology, Physiology, and Weed Science on “aerobiology,” the study of how organisms travel through the atmosphere.

This elective course, which involves hands-on projects in aerobiology, biosecurity, and environmental science, will be offered to students beginning in 2010.

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