Designing a modelling structure for the grapevine downy mildew pathosystem

A process-based simulation model for the grapevine-downy mildew pathosystem was developed in order to quantitatively synthesize the literature available and to provide a tool to guide strategic decisions for disease management. The model includes: i) the main processes involved in the disease dual epidemics on leaves and clusters, from inoculum mobilisation to disease multiplication on foliage, and to infection of clusters; and ii) host dynamics, i.e. crop development, growth, and physiological and disease-induced senescence. A numerical evaluation was performed to investigate the response of the model to changes of the main epidemiological parameters, i.e. the basic infection rate corrected for the removals (RcOPT), the duration of latency period (LP), the duration of infectious period (IP), and the rate of primary infections (P). Increasing values of RcOPT and IP, and decreasing values of LP resulted in a faster increase of the epidemic on both foliage and clusters, while decreasing values of P delayed epidemics. The simulated dynamics of epidemics on foliage and clusters conformed to patterns of dual epidemics observed for downy mildew. The model can be useful for investigating the effect of strategic disease management tools such as the use of resistant varieties or to investigate the behaviour of the pathosystem under scenarios of climate change.