Control of Powdery Scab of Potato: Towards Integrated Disease Management

Abstract

Powdery scab of potato, caused by the plasmodiophorid pathogen Spongospora subterranea f. sp. subterranea, is an increasingly important disease where potatoes are grown in cool/temperate regions. Powdery scab lesions on tubers downgrade their quality as seed, fresh vegetable or processing potatoes, and the disease can severely harm crop productivity. Aspects of the biology of S. subterranea, including long-term persistence in soil, high and rapid reproductive potential, and, possibly, ability to infect alternative hosts, pose considerable problems for development of effective control of powdery scab. Methods shown to reduce the incidence and severity of the disease are reviewed. These include field choice and crop rotation, pathogen detection, use of resistant cultivars, planting disease-and pathogen-free seed tubers, appropriate pesticide treatments for seed tubers and/or infested soil, adjustment of soil nutrient status, and use of suitable management practices during crop growth. No single method is likely to give complete control of powdery scab, particularly where S. subterranea inoculum levels are high on seed tubers or in soil. Effective disease management will therefore depend on implementation of several appropriate methods, using an integrated approach to powdery scab control. This requires understanding of the biology of S. subterranea, and comprehensive and conscientious adherence to appropriate disease control methods during most stages of the potato crop management cycle.

Examples of alien pathogens in Finnish potato production - their introduction, establishment and consequences

“…Certain countries outside the EU important for seed export from Finland have declared S. subterranea a quarantine disease. Besides the risk of carrying powdery scab, and especially PMTV, into healthy fields, S. subterranean-infected seed can cause considerable yield reductions (Falloon 2008). The spraing symptom in tubers is especially severe in cool potato production areas.…”

“…No effective chemical control is currently available (Falloon 2008). PMTV is not classified as a quarantine pest in the EU and no restrictions on its incidence are set at the EU level (European Union 2000).…”

“…In heavily infested fields serious disease outbreaks have occurred after a 12 year break (Falloon 2008). Currently Finnish seed potato is mainly produced in rotations with a 2-3 year break, and other potato crops largely without any crop rotation (Hannukkala et al 2007).…”

“…There are also indications that S. subterranea can invoke galls and develop spore balls (resting spores) in roots of non-solanaceous crops, like oat (Avena sativa L.) and yellow mustard (Sinapis alba L.) (Qu and Christ 2006). The possibility of alternative hosts must be considered in planning crop rotations (Falloon 2008).…”

Powdery scab effect on the potato Solanum tuberosum ssp.andigena growth and yield: andigena

“…These structures contain resting spore aggregations (sporosori), which are highly stress-resistant and can remain dormant in the soil for more than 10 years (Merz et al, 2005). With the lack of efficient control strategies (Harrison et al, 1997;García et al, 2002;Falloon, 2008), powdery scab is a rising issue for both national and international trade, and affects a staple crop with great socioeconomic value and with a profound cultural attachment.…”