The model simulated the development of a single vine stock during a single season. This was coupled with the simulation of inoculum and disease dynamics from primary infection of susceptible leaves and secondary conidial infection as disease spreads from sporulating lesions. Functions, parameterized from the literature or from experimental data, were used to describe growth of the host and spread of the pathogen. The model input variables were environmental (temperature, wind speed and direction) or related to the pathogen (location and onset of primary infection).