ABSTRACT
Plant diseases are not unique to agriculture and are clearly part of natural ecosystems, with localized extinction events not being uncommon for both host and pathogen populations. The effects of epidemics are exacerbated in agriculture, with both intensity and spatial scale being enhanced by crop monoculture and host genetic uniformity. Occurrences of rust epidemics in cereals have been recorded for thousands of years (Kolmer et al. 2009). It was not until the eighteenth and nineteenth centuries that scientific knowledge became available with the realization that the rusts were caused by fungal pathogens, that different forms arose from the same organisms and that macrocyclic life cycles involved five spore types and two very different (heteroecious) host species.
