APS Homepage

TECHNICAL SESSION: Epidemic analysis

Increasing accuracy of strawberry powdery mildew prediction via dynamic simulation modeling
Mamadou L. Fall - Agriculture and AgriFood Canada. Odile Carisse- Agriculture and AgriFood Canada

Strawberry powdery mildew (SPM), caused by Podosphaera aphanis, is gaining in importance as the production of day-neutral strawberry and resistance to fungicide increase. This disease is difficult to predict because of the wide range of weather conditions favorable to its development. Weather, disease (cv. Seascape), and host data collected at three, five and four sites in 2006, 2007 and 2008, respectively, for a total of 12 epidemics were used in this study. First, temperature-based disease risk index and classification trees approach were evaluated but found unreliable under Eastern Canada weather conditions. Hence, we explored dynamic simulation modelling. The model use published algorithms describing subprocesses of P. aphanis life cycle (e.g. sporulation, spore germination, leaf colonization etc.) and assembled knowledge of the interactions among pathogen, strawberry, and weather. The results show an accurate simulation of the trends, shape and amplitude of SPM severity and the relationship between simulated and observed SPM severity was significant in all sites and years (P ? 0.001). The proportion of linear variations in the observed SPM explained by the variation in the simulated disease severity were below 0.70 hence, still need improvement. However, this is the only model that can quantitatively predict the SPM severity and could be combined with the previously developed action threshold to tune fungicide applications strategies.