Cultivar-Dependent Expression of Halyomorpha halys Impact in a Commercial Apple Orchard: Implications for Integrated Pest Management

The brown marmorated stink bug, Halyomorpha halys (Stål), is an invasive pest that increasingly threatens apple production in Europe by causing fruit damage, yield losses, and quality deterioration under commercial orchard conditions. This study investigated seasonal population dynamics, spatial patterns of fruit damage, yield effects, and post-harvest fruit responses of two apple cultivars (‘Cripps Pink’ and ‘Fuji’) in a commercial orchard over two consecutive seasons (2024–2025). Adult and nymphal activity was monitored using pheromone traps, while fruit damage was assessed at harvest across orchard positions and canopy layers. Potential yield losses were estimated based on damage incidence, and selected physicochemical properties of healthy and affected fruits were analysed. Clear cultivar-dependent differences were observed. ‘Fuji’ exhibited typical external feeding damage, with low but consistent damage levels and limited yield losses in both seasons. In contrast, ‘Cripps Pink’ showed substantially higher damage rates and potential yield losses, particularly in 2025; however, classical external feeding damage was not observed. Instead, fruits exposed to H. halys pressure expressed atypical responses, primarily as increased individual fruit mass and size, and atypical skin color patterns, including pronounced striping and uneven pigmentation. Damage in ‘Cripps Pink’ was strongly structured within the orchard, with higher incidence in the upper and middle canopy layers and in areas adjacent to the forest edge, whereas damage in ‘Fuji’ remained low and spatially uniform. Overall, the results demonstrate that the impact of H. halys depends not only on pest pressure but also on cultivar traits and within-orchard spatial heterogeneity. These findings support the development of cultivar-specific and spatially targeted integrated pest management (IPM) strategies that better reflect the uneven distribution and expression of stink bug injury in commercial apple orchards.