Calculation procedure for RITY—A phenology model of Ips typographus

The RITY-2 phenology model was developed for the spatiotemporal simulation of the seasonal development of European spruce bark beetle, Ips typographus. RITY-2 is based on the PHENIPS model and was developed through improving PHENIPS with innovative approaches and calibrating and validating it for Slovenia. RITY-2 predictions are based on air temperatures from Integrated Nowcasting through a Comprehensive Analysis (INCA) system, which is used to calculate the effective bark temperature for beetle development. In this paper we describe the calculation procedure for RITY-2. • INCA enables high resolution spatial and temporal simulations and predictions. • An innovative procedure was introduced that finds the most appropriate spring date threshold from which the calculation of the phenological model is initiated. • Simplified and customized linear models for calculation of the air temperature in the forest and bark temperatures were developed.