Interplay between harvesting, planting density, and ripening time affects coffee leaf rust dispersal and infection

The relationship between the spatial structure of hosts and the individual movement of vectors is central to developing a comprehensive representation of pathogen dynamics. Previous studies have proposed that pathogens like coffee leaf rust (CLR; Hemileia vastatrix) can be transported between plants by coffee workers during harvesting. However, the relative influence of harvesting in coffee rust dispersal and plot-level infection is not well understood, and neither is its relation with plantation characteristics. In this study, we developed a 2D plantation model with deterministically moving agents to explore the role of coffee ripening synchronicity in reproducing the different harvesting trajectories reported in the field. We then evaluate how these trajectories modify the potential CLR infection in plots with increasing planting densities. We found that scenarios with interplant asynchronous ripening and scarcity of trees with berries generate trajectories with medium to long steps that are qualitatively similar to those observed in the field. When coupled with a rust dispersal mechanism, these trajectories significantly increased coffee plot infection compared to scenarios with only local dispersal mechanisms (up to 15%). This effect is enhanced for trajectories with medium-sized steps from the asynchronous scenario, and optimized in plantations with medium planting densities (2000–3000 plants/ha). At high planting densities, plants are always highly infected due to local dispersal, making the contribution of harvest negligible. Our results aims to spur discussion on agroecological practices that can reduce the impact of harvesting and specific trajectories, in scenarios where one can benefit from asynchronous maturation of berries and shaded plantations.