Oral: Dispersal at Multiple Scales: A Key to Outbreak of Disease Epidemics
Physical aspects of Dispersal of Spores of Plant Pathogens.
D. Aylor (1) (1) Connecticut Agricultural Experiment Station, U.S.A.
Spore dispersal involves a series of interconnected biophysical processes, minimally described as take-off, transport, and deposition. Involved are many detailed fluid-particle interactions taking place on length scales ranging from millimeters to hundreds of kilometers. Principles of fluid engineering are used to quantify the motion of spores as they escape the viscous boundary layer near plant surfaces, move through the roughness sublayer, and escape into the convective boundary layer where they can be transported to nearby and distant crops. The initial stages of dispersal occur in a region of highly inhomogeneous turbulence dominated by intermittency. A Lagrangian simulation framework is adapted to examine the journey of a spore during the course of its flight: first as it is released a few millimeters into the air, then as it escapes from the ground cover canopy via turbulent transport, until it is deposited on an infection site. During this journey, we will address the following questions: Which details of the model are most important to dispersal and which of them can be parameterized more simply? When is it necessary to incorporate highly detailed temporal information, when is it sufficient to simply use time-averaged data, and what is the time scale for this averaging? Simplifications used to model spore dispersal will be highlighted to stimulate discussion about where models can be improved, both theoretically and practically.