Spatiotemporal Modelling of Phenology and Population Dynamics of Halyomorpha halys in Emilia-Romagna, Italy

The brown marmorated stink bug (Halyomorpha halys) is a major invasive pest threatening fruit production across Europe. This study integrates spatiotemporal geostatistical modelling with degree-day and photoperiod analyses to characterise its seasonal dynamics in Emilia-Romagna (Italy) from 2020 to 2022. Weekly pheromone trap data were used to quantify developmental succession among Small nymphs (early instars, N1–N3), Large nymphs (late instars, N4–N5), and Adults. Time-series and cross-correlation analyses confirmed consistent developmental delays across years, with Small preceding Large by approximately two weeks and Adults emerging after an additional two to three weeks. However, global inter-stage correlations were moderate (r ≈ 0.4–0.5), indicating substantial spatial heterogeneity among monitoring sites and suggesting that regional averages do not fully capture local population dynamics. To address this variability, a three-dimensional spatiotemporal geostatistical model (space × time) was implemented using Direct Sequential Simulation. The model successfully reproduced seasonal population waves and interannual differences in onset and persistence. The identification of persistent hotspots and stage-specific temporal windows is biologically relevant because it highlights where and when H. halys populations are most likely to increase. As such, from an IPM perspective, these outputs can support earlier monitoring, more precise timing of management interventions, and spatial prioritization of control efforts. These findings demonstrate that combining stage-specific temporal analysis with spatially explicit modelling improves forecasting accuracy and supports more precise timing of biological and chemical interventions. The proposed framework provides a scalable tool for climate-responsive integrated pest management in fruit-growing systems.