Pacific Northwest 1998 An Online Guide to Plant Disease Control

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Potato (Solanum tuberosum) -- Scab (Common)
 
Cause: Streptomyces scabies, a filamentous bacterium that lives in soil and on diseased tubers. Neutral or alkaline soils favor scab development. Russet cultivars are generally less affected than smooth-skinned cultivars and should be grown where scab has been severe.
Symptoms: Corky lesions appear on the tuber's surface. Lesions may be small and superficial or consist of deep pits.

Note the roughened exterior of these tubers.

Scab symptoms on a potato tuber.

 
Cultivar Resistance: The Russet cultivars, 'Norgold', 'Nooksack', 'Russet Burbank', and 'Targhee' have good resistance. 'Red Norland' has moderate resistance.
Cultural control:

  1. Use certified seed potatoes.
  2. Use tolerant cultivars where possible.
  3. High soil moisture for 1 week before emergence and 8 weeks after reduced scab in 'Russet Burbank'. High moisture is defined as 80% or above of available moisture, measured at 9 inches in the soil.
  4. On calcareous soils, postplant sidedress applications of triple-superphosphate suppressed common scab, even when soil phosphate levels were greater than 20 ppm.
References:
Davis, J.R., and J. Garner. 1978. Common Scab of Potato. University of Idaho Current Information Series Publication 386.
Content edited by: Cynthia M. Ocamb on January 1, 2009
 
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