Dr. Hansen has developed an international reputation for his contributions to understanding the biology, population dynamics, and management of diseases of forest conifers. He has addressed virtually every disease of economic concern in conifers in the Pacific Northwest. Together, they have shown how endemic root pathogens can shape the long-term patterns of species compositions of forests by creating mortality centers that subsequently are invaded by other conifer species less susceptible to these pathogens. Recently, real-time polymerase chain reaction was used to monitor pathogen populations in Douglas fir, an approach that will certainly shape future epidemiological studies. In 1999, Dr. Hansen organized a new research working group, “Phytophthora Diseases of Forest Trees” to consider the effects of Phytophthora species as endemic and invasive pathogens in natural ecosystems. Dr. Hansen has trained M.S. and Ph.D. students, collaborated with postdoctoral trainees, and served on graduate committees of students from Oregon State University and abroad. In addition, he serves as an advisor for 15 to 20 biology and botany undergraduate students. He has taught a variety of advanced graduate courses in plant pathology as well as large general botany courses. Dr. Hansen has achieved the statue of a world authority in forest pathology and it is fitting that he receives the APS Fellow Award.