title: A Quantitative Dynamic Simulation of Bremia lactucae Airborne Conidia Concentration above a Lettuce Canopy.
abstract: Lettuce downy mildew, caused by the oomycete Bremia lactucae Regel, is a major threat to lettuce production worldwide. Lettuce downy mildew is a polycyclic disease driven by airborne spores. A weather-based dynamic simulation model for B. lactucae airborne spores was developed to simulate the aerobiological characteristics of the pathogen. The model was built using the STELLA platform by following the system dynamics methodology. The model was developed using published equations describing disease subprocesses (e.g., sporulation) and assembled knowledge of the interactions among pathogen, host, and weather. The model was evaluated with four years of independent data by comparing model simulations with observations of hourly and daily airborne spore concentrations. The results show an accurate simulation of the trend and shape of B. lactucae temporal dynamics of airborne spore concentration. The model simulated hourly and daily peaks in airborne spore concentrations. More than 95% of the simulation runs, the daily-simulated airborne conidia concentration was 0 when airborne conidia were not observed. Also, the relationship between the simulated and the observed airborne spores was linear. In more than 94% of the simulation runs, the proportion of the linear variation in the hourly-observed values explained by the variation in the hourly-simulated values was greater than 0.7 in all years except one. Most of the errors came from the deviation from the 1:1 line, and the proportion of errors due to the model bias was low. This model is the only dynamic model developed to mimic the dynamics of airborne inoculum and represents an initial step towards improved lettuce downy mildew understanding, forecasting and management.
authors.affiliation: Biology Department, University of Sherbrooke, 2500 De l'Université Blvd., Sherbrooke, QC, Canada, J1K 2R1.|Compagnie de Recherche Phytodata inc., 111 Rang Saint-Patrice, Sherrington, QC, Canada, J0L 2N0.
authors.forename: Mamadou Lamine
authors.initials: ML
authors.lastname: Fall
authors.affiliation: Compagnie de Recherche Phytodata inc., 111 Rang Saint-Patrice, Sherrington, QC, Canada, J0L 2N0.
authors.forename: Hervé
authors.initials: H
authors.lastname: Van der Heyden
authors.affiliation: Horticulture Research and Development Centre, Agriculture and Agri-Food Canada, 430 Gouin Blvd., St-Jean-sur-Richelieu, QC, Canada, J3B 3E6.
authors.forename: Odile
authors.initials: O
authors.lastname: Carisse
mesh_terms: D000391:Air Microbiology; D018545:Lactuca / Q000382:microbiology*; D056004:Molecular Dynamics Simulation; D009868:Oomycetes / Q000254:growth & development / Q000502:physiology*; D010935:Plant Diseases / Q000382:microbiology; D012044:Regression Analysis; D013170:Spores / Q000254:growth & development / Q000502:physiology*