We are investigating the forces generating the spatial pattern of infection by looking at the plant Phlox paniculata and the powdery mildew. Diseased plants may be clumped because of a spatial pattern of resistance to the disease, because of environmental patchiness, or because the limited dispersal ability of the pathogen prevents distant plants from getting infected. We will examine this question by constructing and comparing spatial maps of disease resistance, environmental conditions, and disease occurrence in an intact Phlox population. In addition, we will determine if spatial patterns of disease resistance are created because near neighbors are close relatives which share similar resistance. Genetic relatedness will be determined by DNA analysis. Disease resistance will be determined by inoculation tests. Environmental factors will be monitored using computer controlled sensors, and disease occurrence will be monitored by weekly censusing. By understanding the factors controlling disease spread in Phlox paniculata, we will better understand how all plant diseases spread.
