Integrating spore dispersal and models of turbulence

Airborne spores spread many of the world's most important plant diseases. The challenges of controlling diseases with minimum use of pesticides, both locally and on a regional scale, require that we be able to quantify spore transport over distances ranging from millimeters to tens of kilometers. These spores are microscopic in size. To become airborne initially, spores are either entrained from air layers a few hundred microns thick above a surface or they are actively released a few millimeters to centimeters into the air, in some cases at ground level. In either case, the initial motions of the spore transport depend on the interaction of turbulence scales ranging from millimeters to tens of meters. We believe that the challenges of predicting the initial entrainment, escape from the crop canopy air space, and the long-range atmospheric transport can best be met by integrating these turbulence length scales via the marriage of Particle Trajectory Analysis and Large Eddy Simulation. We will set out a plan for doing this integration and will discuss the physical aspects of the problem using specific crop-pathogen systems as examples.