  The dispersion of plant pathogens, such as rust spores, is responsible for
more than 20% of global yield loss annually, and poses a significant threat to
human health. However, the release mechanics of pathogens from flexible plant
surfaces into the canopy is not well understood. In this study, we investigated
the interplay between leaf elasticity and raindrop momentum, revealing how it
induces flow coherence and enhances spore transport with 2-10 times greater
energy compared to impacts on stationary surfaces. We observed that a flexible
leaf generates vortex dipoles, leading to a super-diffusive stream flow. We
then developed a theoretical model that accurately predicted the average air
flux from leaf edges and the vortex strength to be proportional the vibration
speed of the leaves. With Lagrangian diagnostics, we further revealed the
presence of hyperbolic and elliptical coherent structures around fluttering
leaves, providing the dynamical description of spore transport. Our model
demonstrated that a leaf aspect ratio (length/width) negatively correlates with
dispersion, indicating that shorter and wider leaves promote greater pathogen
spread. Additionally, we found that leaf rigidity positively correlates with
dispersion due to damping effects. These mechanistic insights would help the
construction of physically informed analytical models for improve local crop
disease management.
