Seminar Summary - I will highlight our lab’s current projects which explore the effects of large- and small-scale climate variation on the ecology and evolution of plant diseases. Our focal system for this work involves natural populations of Plantago host plants and their powdery mildew pathogens. We use observational, experimental, and theoretical approaches to study these plant-fungus interactions along a large latitudinal gradient (spanning from southern Louisiana to northern Minnesota) and across an urbanization gradient in St. Louis, Missouri. Key research questions we have recently asked include: How does climate shape the geographic distribution and seasonality of powdery mildew on Plantago around the world? Are powdery mildew strains locally adapted to temperature or to host genotypes along a latitudinal gradient? In what geographic regions and seasons can powdery mildew undergo sexual reproduction? How do powdery mildew dynamics vary within and between host populations across a gradient of urbanization? Why are there larger powdery mildew epidemics in more urban populations? Our answers to these questions fill critical gaps in understanding wild plant-pathogen interactions in an increasingly warm and urbanized world.