Plant biologists and engineers have extended their studies to the skies to track airborne pollen once it leaves a crop.
In a new study, published in Environmental Monitoring and Assessment , researchers established an accurate methodology for tracking, measuring, and forecasting pollen dispersal of genetically engineered switchgrass at both the ground and atmospheric levels.
"This is the first study to bring all these elements together in one experiment," said first author Manu Nimmala Ph.D. '26. "We combined genetically engineered switchgrass that produced fluorescent pollen, novel drone and ground-based sampling systems, high-resolution wind measurements, and atmospheric dispersal simulations to connect measured pollen concentrations with pollen release from the source field."
A genetically engineered crop has DNA that has been intentionally modified to introduce a specific trait.
According to David G. Schmale III, professor of plant and environmental sciences, the atmosphere is one of the least-sampled ecosystems. An increased understanding of how pollen moves through the atmosphere can help improve strategies for managing the movement of pollen and genes between neighboring plants, protecting seed production systems, and forecasting airborne allergens.
"Pollen is an airborne particle with important implications for agriculture, ecosystems, and human health," said Schmale.
Those with allergies may appreciate the ability to accurately predict pollen distribution in the atmosphere, but pollen can also be a nuisance for crops and farmers.
"Farmers can build fences to keep livestock out, but fences don't stop pollen, plant pathogens, or tiny insects from moving across the landscape," said Schmale, director of the Translational Plant Sciences Center . "That invisible movement is what makes atmospheric biology both so challenging and so important to understand."
In this case, the researchers engineered the switchgrass to produce an orange fluorescent protein in its pollen, allowing them to distinguish it from naturally occurring pollen in the environment. Drones equipped with air sampling devices that draw in airborne particles into a liquid solution were then flown over the genetically engineered crop. In addition, two other kinds of air-sampling devices measured the pollen transfer on the ground level.
"A sampler can tell you that pollen was in the air, but it doesn't automatically tell you how it got there," said Nimmala, currently a postdoctoral fellow in engineering mechanics. "The goal was to connect what we captured to the field and the meteorology."
The team found that pollen movement could be measured using a combination of ground- and drone-based sampling systems. High-volume ground samplers were the most effective at capturing pollen from the small field source, while drone-based samplers demonstrated the ability to collect pollen above and downwind from the field source. The genetically engineered switchgrass also provided a proof of concept for tracking pollen movement in the atmosphere using fluorescent markers.
The results showed that pollen release rose in the early afternoon and was shaped by weather, especially wind speed, humidity, and temperature. When winds were slow and shifting, shorter wind-averaging windows helped the model better follow the plume.
"We found that it's really important to include changing wind directions when predicting where pollen travels," Nimmala said. "When we accounted for that, the modeled prediction better matched what we measured in the field."
Switchgrass was used for the research, according to Schmale, because it is a leading perennial bioenergy crop in the United States, sharing it can produce large amounts of biomass but requires less input than corn.
"That is one reason regulators want a strong understanding of how pollen and genes move through the environment before new varieties are deployed as scale," Schmale said.
And that is the next step: to scale up.
Other researchers who participated in this study include:
- Landon Bilyeu, former graduate research assistant, plant and environmental sciences, Virginia Tech
- Hosein Foroutan, associate professor, civil and environmental engineering, Virginia Tech
- Hope A. Gruszewski, laboratory technician, research specialist senior, Virginia Tech
- Regina Hanlon, research associate, Virginia Tech
- Reginald J. Millwood, research assistant professor, University of Tennessee
- Tyler Newton, assistant technology transfer manager, University of Tennessee
- Craig Powers, former postdoctoral fellow, plant and environmental sciences, Virginia Tech
- Shane Ross, professor, aerospace and ocean engineering, Virginia Tech
- Charles Neal Stewart Jr., professor, University of Tennessee
- Jessica Stockdale, graduate research assistant, University of Tennessee
Original study : DOI10.1007/s10661-026-15632-3
