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Atmospheric dispersal of plant pathogens over multiple spatial and temporal scales

Donald Aylor: The Connecticut Agricultural Experiment Station

<div>Knowing how far and how fast disease will spread in a region allows growers and land managers to plan. We present a biophysical model for diseases spread by airborne spores that predicts their distance and rate of spread. The model’s principal components are distance between fields, meteorological conditions at various scales, dynamics of pathogen buildup, and development of the host. Our model spans four length scales: 1) plant canopy height, 2) field size, 3) regional scale, and 4) continental scale, and four time scales: a) rate of epidemic development, b) infectious and latent period of the pathogen, c) pathogen survival time, and d) the return period of conditions conducive for transport and infection. All eight scales together determine the time for new infections to appear in distant fields, which allows risk to be evaluated for patches of hosts distributed widely across a landscape. At field and farm scales, dispersal is a more-or-less continuous process; while at regional and continental scales dispersal is discontinuous, needing to span the distances between patches of host. This fundamental difference is one reason that wave front speeds are apparently faster on long rather than on short distance scales and it allows for the existence of critical separation distances that can stifle disease spread. The model will be illustrated using apple scab, potato late blight, tobacco blue mold, and stem rust of wheat as examples.</div>

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