ELABORATION AND VALIDATION OF A DYNAMIC MODEL FOR PRIMARY INFECTIONS OF PLASMOPARA VITICOLA IN NORTH ITALY

A dynamic model simulating the life cycle of Plasmopara viticola, from overwintering oospores to the appearance of pri- mary symptoms on grape leaves, was elaborated in order to obtain accurate and robust information about the risk for downy mildew infections during the primary inoculum season. The model was elaborated according to the systems analysis, and takes into account the following stages of the infection cycle: oospore maturation and germination, survival of zoosporan- gia and zoospore ejection, survival and dispersal of zoospores, infection and incubation. The model allows to evaluate hourly the progress of the infection process, and to estimate the period of disease symptom onset. The model was validated against data not used for model elaboration. Hourly meteorological data were collected under different epidemiological conditions (several locations and years) in northern Italy (Piedmont, Oltrepò Pavese, and Emilia-Romagna), and simula- tions were compared with actual disease appearance observed in vineyards. The model proved to be accurate and robust.