Dr. Yuen's research focuses on the biological control of diseases caused by fungal pathogens. He investigates plant associated bacteria and fungi that can be applied as antagonists against Rhizoconia and Phtyium, two genera of fungi destructive on agronomic plants and turf grass. He also studies the role of bacteria resident on bean foliage and blossoms in the suppression of white mold disease of dry edible bean. His activities involve applied research in the form of laboratory and field testing of potential biocontrol agents and delivery methods. In addition, he conducts basic research encompassing the ecology of microbial antagonists and the mechanisms by which antagonists inhibit disease.