Edge effects, not connectivity, determine the incidence and development of a foliar fungal plant disease

Using a model plant-pathogen system in a large-scale habitat corridor
experiment, we found that corridors do not facilitate the movement of
wind-dispersed plant pathogens, that connectivity of patches does not
enhance levels of foliar fungal plant disease, and that edge effects
are the key drivers of plant disease dynamics. Increased spread of
infectious disease is often cited as a potential negative effect of
habitat corridors used in conservation, but the impacts of corridors
on pathogen movement have never been tested empirically. Using sweet
corn (Zea mays) and southern corn leaf blight (Cochliobolus
heterostrophus) as a model plant-pathogen system, we tested the
impacts of connectivity and habitat fragmentation on pathogen movement
and disease development at the Savannah River Site, South Carolina,
USA. Over time, less edgy patches had higher proportions of diseased
plants, and distance of host plants to habitat edges was the greatest
determinant of disease development. Variation in average daytime
temperatures provided a possible mechanism for these disease patterns.
Our results show that worries over the potentially harmful effects of
conservation corridors on disease dynamics are misplaced, and that, in
a conservation context, many diseases can be better managed by
mitigating edge effects.