Novel community assembly and the control of a fungal pathogen in coffee agroecosystems

Ecological principles are frequently leveraged when considering the control of animal pests of crops. Still, pathogens have not generated similar research despite the current interest in the field of disease ecology. Here we use the most economically significant pathogen of coffee, the coffee leaf rust, Hemileia vastatrix, to understand the role of top-down control in its regulation. Large-scale sampling of the pathogen and its natural enemy community in Puerto Rico and Mexico reveal striking differences in the potential for biological control. Four main natural enemies are identified, a fungal parasite, a dipteran fungivore, a mite fungivore, and a snail generalist in Puerto Rico, with only two occurring frequently in Mexico. We suggest that the community of natural enemies is potentially an important mechanism contributing to the maintenance of the pathogen at relatively benign levels in Puerto Rico. We provide evidence that management is a contributing factor and is perhaps operative in part through its effect on the natural enemies of the pathogen. This work has applied significance not only for coffee production in Puerto Rico but also for understanding how this pathogen may be controlled in areas where it has been, and potentially will be, at epidemic status.