Virginia Tech researchers discovered that wheat plants “sneezing” off condensation can vastly impact the spread of spore-borne diseases, such as wheat leaf rust, which can cause crop yield losses of up to 20 percent or more in the United States and higher average losses in less developed agricultural nations. The study, published in June, and featured on the cover of the Journal of the Royal Society Interface, is part of a three-year grant obtained from the U.S. Department of Agriculture’s National Institute of Food and Agriculture to study the dispersal of wheat pathogens by rain splash and jumping-droplet condensation.
Jonathan Boreyko, assistant professor of mechanical engineering in the College of Engineering is a co-principal investigator on the grant and David Schmale, professor of plant pathology, physiology, and weed science in the College of Agriculture and Life Sciences, is the primary investigator. “Professor Schmale had seen some of the work we’ve been doing on condensation and was curious to see what we could learn about condensation on wheat leaves,” said Boreyko. “The project didn’t start with any expectations, but people already knew that rain splash and wind caused pathogenic spores to be removed from plants and spread to others, and we wanted to see if condensation might also have a role to play in spore dispersal.”
“Conceptually, what the plants are doing is sneezing,” Boreyko said. “The jumping droplets, at the rate of 100 or more an hour, are a violent expulsion of dew from the surface. It’s good for the plant because it is removing spores from itself, but it’s bad because, like a human sneeze, the liquid droplets are finding their way onto neighboring plants. Like a cold, it’s easy to see how a single infected plant could propagate a disease across an entire crop.”
The paper, co-first-authored by Saurabh Nath and Farzad Ahmadi, engineering mechanics graduate students in Boreyko’s lab, showed the jumping droplets can dramatically increase the dispersal of disease spores. “We wanted to find out, first if the condensation droplets can carry spores, and while 90% of them carry only a single spore, we have seen instances where a droplet has carried as many as 11,” Ahmadi said. “We also looked at how high the spores can jump and whether they can get past the boundary layer of the leaf.”
The boundary layer, which is about a millimeter thick, is the region of air near the leaf’s surface where the wind doesn’t affect the droplet. If the kinetic energy from merging moves the jumping droplet above the boundary layer, the droplet can be taken by the wind. Depending upon the wind speed, it’s feasible for the droplet to then be moved great distances, including to neighboring fields or farms
Taken from the excellent ISPP Monthly Newsletter – click here to check it out.