Connecticut Agricultural Experiment Station
Abstract: Devastating plant diseases are spread by airborne spores, sometimes over long distances. I will describe models of spore dispersal that could be used to help assess the potential for airborne spread of disease between nearby and distant fields. Dispersal is comprised of a series of interconnected biophysical processes, minimally described as take-off, transport, and deposition. These processes involve detailed fluid-particle interactions governed by 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. Initial stages of dispersal occur in a region of highly inhomogeneous turbulence dominated by intermittency. Lagrangian simulation models are adapted to describe some principal elements of this problem. To help tie together the great range of distance scales involved in aerial dispersal, I will examine the fate 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 a target leaf. Several of the simplifications used to model the biology and the fluid dynamical interactions will be highlighted with the expressed aim of stimulating discussion about where these models can be improved, both theoretically and practically.
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