Habitat corridors are a commonly proposed method of counteracting the negative effects of habitat fragmentation. The addition of corridors may change the shape and edge-to-area ratio of habitat patches, which may have unintended and perhaps deleterious consequences to ecological processes. Increased transmission of disease has been proposed as a possible negative impact of corridors, but no empirical studies have examined the role corridors play in disease spread. Working in the Savannah River Site Corridor Experiment, the largest experiment to test for the effects of corridors, I investigated the effects of patch shape, connectivity, and distance to edge on the dispersal and incidence of Southern Corn Leaf Blight (Bipolaris maydis) on potted corn (Zea mays) plants. I hypothesized that habitat connectivity and patch shape affect presence and severity of plant disease by altering the movement of disease propagules or causing variation of microclimate conditions (edge effects).

Results/Conclusions

I found that patch shape significantly affected disease presence, as patches with a low edge-to-area ratio had a higher proportion of infected plants. Corridors did not increase disease incidence by increasing connectivity. Distance to edge did not significantly affect disease presence, but surveys of resident plant species show that disease severity may be higher closer to habitat edges, probably due to microclimate conditions. If my model system generalizes to other plant-pathogen systems, then it suggests that conservation managers should not worry about the effects of corridors in spreading disease, but rather should focus on mitigating the effects of habitat edges.