Equations for the distribution of Venturia inaequalis ascospores versus time during infection periods

Distribution of Venturia inaequalis ascospores versus time during an infection event was investigated by integrating in a dynamic simulation model the available knowledge on the biology of infection processes and the effect of environmental conditions. Processes of spore immigration on leaf surface, germination, appressorium formation, and successful infection establishment were incorporated into the model by elaborating mathematical equations depending on air temperature and length of the wet period. Survival of spores belonging to different development stages (ungerminated, germinated, with appressorium) was also included in the model as a function of temperature, relative humidity, and duration of wetness interruption. Based on comparison with previously published data the architecture of the model and its algorithms can be considered accurate and robust. Nevertheless, validation of model simulations under orchard conditions will be necessary before its use in management decisions.