The release of ascospores of Venturia inaequalis and V. pirina in the field, the apple scab infection criteria and the frequency of infection periods were investigated in Victoria. Ascospores were trapped over 3 months from green-tip in early September until late November over six years. In most seasons, the majority of ascospores from both species were trapped during the period of bloom but in years with extended dry periods (> 7 days) during bloom, ascospore release was significantly delayed. Ascospore release was triggered mainly by free moisture from rainfall and by light, but also occurred during periods of dew. In all seasons, less than 17.5% of a season’s ascospores were trapped during darkness (e.g. 1900 to 0500 h). In a field study usingpotted plants, the Mills’ criteria, itsrevised version and the Schwabe index predicted apple and pear leaf scab infections during wetting events in which leaf wetness began during day-time (0600 to 1900 h) and ascospores were trapped at the start of the wet periods. In two fruit-growing regions of Victoria, infection periods began on average 8–12 days apart and the average length of an infection period was 20 h. The use of weather information and ascospore release events is discussed in relation to the forecasting of apple and pear scab for effective scab control.