Review: Powdery Scab of Potato-Increased Knowledge of Pathogen Biology and Disease Epidemiology for Effective Disease Management

The importance of the potato tuber disease powdery scab, caused by the zoosporic pathogen Spongospora subterranea f. sp. subterranea, has increased worldwide, and the disease is one of the most important problems facing potato production in some regions. This soilborne pathogen produces many resting spores which can remain dormant for long periods, are highly resistant to environmental stresses and can spread the disease on seed potatoes and in contaminated soil. The enigmatic nature of this organism exacerbates the development of effective powdery scab control methods. Substantial knowledge has been gained in the last decade on the biology of the pathogen and the epidemiology of the disease, but no single effective control measure is, or is likely to be, available. An integrated approach to powdery scab management is the aim, with host resistance as a substantial and sustainable component. Further research on the epidemiology of powdery scab and population genetics of the pathogen is urgently required. All stakeholders involved in the potato industry must become aware that solution of the powdery scab problem is likely to be a long-term goal. When resistant cultivars with all the other characteristics demanded for marketing high-quality potatoes are available, and when disease risk from the pathogen on seed and/or in soil can be accurately determined, then the mission to develop effective powdery scab control will become achievable.