Abstract: A warning Service for pests and diseases of the most important crops was set up in Emilia-Romagna region (Italy) in 1997. Integration of information obtained by forecasting models and fields surveys is used to develop warnings concerning the risk of pest/disease attack. For the control of Cydia pomonella is available a phenological time–distributed delay model. Biological parameters were defined in 1991 in lab-trials. On the basis of hourly temperature, the model can simulate the development of the first and second generation. It gives as output the cumulating percentages of egg-laying, egg-hatching, pupation and adult emergence as well as the age structure of the population. The model has been fully tested over 1992-1998 and therefore has been effectively used for ten years in Emilia-Romagna to optimize control strategies in IPM.From the first application in 1998, it was executed steadily a quality control of simulated data by their comparison to that observed in orchards. As the pheromone traps do not always describe population dynamics properly, it has been chosen to assess the oviposition activity.Weekly field observations were carried out over 1998-2008 in an untreated orchard near Bologna.The eggs were examined for the exact phase of embryonic development determination. Then the egg laying dates were estimated taking into account of specific degree-days for each embryonic phase.Results from the comparison between the simulated data and those observed in field are reported.Altogether, actual and simulated oviposition curves agree fairly well over the last eleven years despite the different climatic condition recorded in this period.