Use of the A-scab model for rational control of apple scab

A-scab is a dynamic model for Venturia inaequalis primary infections. It simulates ascospore maturation, ejection, deposition, and infection during the season based on hourly data of air temperature, rainfall, relative humidity, and wetness duration. A-scab produces a risk index for each infection period and predicts the time of disease onset. Since the validation works showed that the model produces accurate and robust predictions, a 3-year (2006 to 2008) experiment was carried out in order to determine the possibility of using A-scab for scheduling fungicide sprays. Trials were performed in northern Italy (at Ravenna and Bologna) by comparing: i) untreated control, ii) farming practice, iii) A-scab recommendations. The disease incidence on both leaves and fruits in the plots sprayed according to A-scab predictions did not change significantly relative to the farm practice. The use of A-scab led to a general reduction in the number of fungicide applications.