Interactions between agroecology and disease ecology at multiple scales
Despite the ubiquity and potential importance of pathogens in plant communities, our understanding of the factors that govern disease spread is still rudimentary. Agroecosystems serve as excellent systems for studying the ecology of plant disease. Although still replete with complex interactions, these ecological communities are relatively simple compared to unmanaged ecosystems, and the components of the system are often well characterized. We have used agroecosystems and their component species as model systems to understand the dynamics of disease spread at multiple scales. Most disease research focuses on single pathogens infecting single hosts, but infections of a single host by multiple pathogens are common in nature, and pathogens with multiple host species are also widespread. Using experimentally tractable agroecosystems, we have addressed the role of landscape heterogeneity, host diversity, host spatial arrangement, and pathogen diversity in shaping disease transmission and virulence.
Field and greenhouse experiments, accompanied by on-farm surveys, demonstrate feedbacks between host community structure and disease dynamics, along with strong effects of landscape heterogeneity and pathogen diversity on disease spread and virulence. Coinfection by multiple pathogens can modify ecological dynamics through effects on transmission and virulence, while allowing recombination among closely related pathogens. Agricultural management strategies at the farm level can limit or enhance such changes in the pathogen community, while ecosystem heterogeneity in agricultural landscapes can influence disease prevalence through effects on vectors, their natural enemies, and pathogen reservoirs. These processes can drive disease dynamics in both natural and agricultural plant communities.