Potato Review Group

Contents

Background

Risk of powdery scab

Reducing the risk of powdery scab

Further information

Powdery scab notes

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Background

  1. Powdery scab (Spongospora subterranea) fungal inoculum may be seed or soil borne. More …
  2. Powdery scab is considered to occur on the majority of land where potatoes are grown but there is no commercial test for levels of inoculum in soil. More …
  3. Infection of tubers occurs through lenticels before they are suberised (usually before tubers reach 20 mm) but roots may also become infected. More …
  4. Disease development begins before infection becomes visible  and symptoms continue to develop throughout the season. More …
  5. The risk of infection increases as soil pH increases. More …

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Risk of powdery scab

  1. Powdery scab requires wet, probably waterlogged, soil. More …
  2. Wet soil enables motile zoospores to transfer from the seed tuber, or spore balls in soil, to growing plants. More …
  3. Over watering should be avoided during tuber development and early tuber growth.
  4. Avoid growing susceptible cultivars on sites with a history of powdery scab or which are liable to become waterlogged.
  5. Inoculum can be introduced to clean soil by planting infected seed tubers.
  6. The following have been reported to be alternative hosts (more …):
    • oilseed rape, sugar beet, spinach
    • chickweed, poppy, nettle, fathen
  7. Powdery scab can transmit potato mop top virus (PMTV), a cause of spraing. More …

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Reducing the risk of powdery scab

  1. There is no seed treatment for control of powdery scab and no evidence of suppression by fungicides applied in-furrow. More …
  2. The risk of infection may be lower on soils with a high zinc concentration and application of zinc products to seed or soil has therefore been suggested to be beneficial but there is little evidence of more than suppression of disease. More …
  3. Ensure good drainage and appropriate irrigation, particularly during early tuber formation (up to 20 mm tubers). More …
  4. Cultivars differ in susceptibility and use of a resistant cultivar is one of the most effective measures of control. More …
  5. Use cultivars with low susceptibility to powdery scab at sites with a risk of infection (see Potato Variety Database).

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Further information

Powdery scab notes

Transmission of seed borne diseases 2018 (Inoculum transfers from seed to growing plant via motile zoospores)

Blemishing disease updates 2011 (Development of infection before it is visible; transmission potato mop top virus – a cause of spraing)

Tuber blemishing diseases 2006 (Includes powdery scab: detection and quantification in soil and on tubers; effects of seed and soil inoculum; survival of spore balls; alternative hosts; cultivar resistance; experiments on control)

Powdery scab 2001 (Importance of lentil development in susceptibility to infection)

Tuber blemishing diseases 1999 (Includes powdery scab: importance of the environment for disease development)

Tuber blemishing diseases 1998 (Includes powdery scab: seed and soil borne inoculum)

Powdery scab (Life cycle; biology; environmental conditions; investigations into control)

 

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