A study explores how raindrops help spread plant pathogens. Rainfall aids the spread of plant pathogens such as fungal spores across long distances. When rainfall splashes on surfaces, drops laden with rain-drenched spores and less than 100 μm in width can be carried by wind to susceptible plants. However, the precise mechanism by which large raindrops, which are too heavy to become airborne, mobilize dry spores upon hitting infected plant surfaces remains unclear. Sunghwan Jung and colleagues used high-speed photography and modeling to visualize and compute how individual raindrops liberate and transport dry spores of the wheat rust fungus Puccinia triticina from infected wheat plants. Upon impact with the leaf surface, a single raindrop liberates thousands of dry dispersed spores, the number of spores increasing with impact velocity. Analysis revealed that the impact generates an air vortex ring around the raindrop that lasts for tens of milliseconds; the vortex ring, which increases the height to which the spores are ejected, sends the spores aloft in a swirling motion, exposing them to the wind and potentially enabling their transport away from leaf surfaces, beyond leaf boundaries, and across several kilometers. According to the authors, raindrop-induced air vortex rings may thus play a crucial role in the long-distance dry dispersal of plant pathogens.
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Article #18-20318: "Vortex-induced dispersal of a plant pathogen by raindrop impact," by Seungho Kim, Hyunggon Park, Hope Gruszewski, David G. Schmale III, and Sunghwan Jung
MEDIA CONTACT: Sunghwan Jung, Cornell University, Ithaca, NY; e-mail: < sunnyjsh@cornell.edu >
Proceedings of the National Academy of Sciences