The incorporation of pathogen spores into rain-splash droplets : a modelling approach

Simple, theoretical, physical principles and existing experimental data were used to derive an analytical model to describe thr incorporation of plant pathogen spores into splash droplets, Data were obtained from experiments on splash dispersal of spores of Pseudocercosporella herpotrichoides (cereal eyespot), Pyrenopeziza brassicae (oilseed rape light leaf spot) and Septoria nodorum (wheat glume blotch). In these experiments, incident drops of diameter 4-5 mm were allowed to fall onto spore suspensions 0.5 mm deer with 1.2 x 10(5) to 6.5 x 10(5) spores:ml. The analytical model was constructed as the product of thr ee functions of droplet diameter which described, respectively, the frequency distribution of droplet diameters, the proportion of droplets carrying spores and the mean number of spores in spore-carrying droplets in each diameter category. The frequency distribution of droplet sizes was described by ii log-normal distribution, the proportion of droplets carrying spores was described by an exponential function and the adimensional spore concentration in spore-carrying droplets was described by a Fewer law. The cumulative proportions of spores in droplets in diameter categories of increasing diameter were calculated ii, compare observed and fitted data.