This project investigated the epidemiology and control of powdery scab of potatoes. In tests under controlled conditions in the glasshouse, the fungus causing powdery scab infected the roots of several species of plants grown in rotation with potatoes. The severity of infection was highest on the roots of tomato seedlings used as controls, lowest on wheat, barley, perennial ryegrass, linola, and intermediate on canola and “Pasja” rape. Initial experiments showed that a bioassay using tomato seedlings could potentially be developed as a research tool to study the effect of control strategies on the populations of the pathogen in soil. A preliminary glasshouse trial showed that the treatment of seed potatoes with disinfectant or protectant fungicides could reduce the carry-over of powdery scab to progency tuber but further work is needed to develop effective seed treatments.