Landscape structure influences the spread of plant pathogens, primarily by affecting pathogen dispersal. Coffee leaf rust (Hemileia vastatrix), a fungal disease that causes heavy economic losses in the coffee industry, is likely to be affected by landscape structure via dispersal of its wind-borne spores. Previous studies have found positive associations between leaf rust incidence and the proportion of nearby pasture cover, suggesting that deforestation may facilitate rust spore dispersal. We explored this idea by modeling the spread of rust transmission in simulated landscapes. Specifically, we modeled within-patch transmission using a probabilistic cellular automata model, and between-patch transmission using a random walk with spore movement inhibited by forest canopy cover. We used this model to understand how the spread of coffee rust is affected by 1) clustering of coffee, 2) clustering of deforestation, and 3) proportion of landscape deforestation.
Results/Conclusions
We found that clustering of coffee is the primary driver of rust transmission, affecting the likelihood and severity of disease outbreaks in a landscape context. However, our results also suggest that there may be some threshold below which the proportion and clustering of deforested areas become important drivers of coffee rust transmission. Specifically, landscapes with more deforestation and in which deforested areas are less clustered are more prone to rust outbreaks.