My research program focuses on the ecology and epidemiology of plant pathogens transmitted by insects. There is increasing recognition that pathogens can have dramatic impacts on host populations and community structure and dynamics, but little is known about the ecology of plant viruses or other insect-transmitted pathogens. My research explores how plant community structure in both natural and agricultural ecosystems influences the epidemiology of insect-borne pathogens of plants. I have been particularly interested in understanding the role of vector movement in driving pathogen epidemiology, and I have examined how plant species diversity, host genetic diversity, and plant density and dispersion affect vector movement and disease spread. I have addressed these issues in disease systems in the northeast U.S., in Central America, and in Thailand. In recent years, I have used the aphid-transmitted barley yellow dwarf virus, a widespread pathogen of grasses, as a model system to address other aspects of the interactions between viruses, vectors and host plants. Projects have addressed the impact of virus infection on host plant preference of vector insects, direct and indirect competition between viruses, virus spread between crop hosts and wild host plants, the impacts of virus infection on wild grass hosts, and the ecological risks of transgenic virus resistance in crops. This work is intended to contribute to the design of environmentally benign agricultural systems, as well as to improve our understanding of disease ecology in natural plant communities.