Pacific Northwest 1998 An Online Guide to Plant Disease Control

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OSU Extension Office
 
Potato (Solanum tuberosum) -- Pink Rot
 
Cause: Phytophthora erythroseptica, a soilborne funguslike organism. The disease is directly associated with high soil moisture when tubers approach maturity. It becomes a problem in storage by encouraging the development and spread of soft rot. Pink rot does not spread in storage by spore movement (as Late Blight does) but grows from tuber to tuber.
Symptoms: Internal rotted tissue is a dirty, creamy white at first, appearing water soaked yet leathery; the texture has been described as like a cooked potato. On exposure to air, it turns pink, later becoming darker brown. There is a definite margin between rotted and healthy tissue. This organism does not cause a cavity like that of dry rot.

Note the dark line at the advancing edge of the rotted tissue.

After affected tubers are cut, the infected tissues change to pink, brown, and black shortly after being exposed to air.

 
Cultural control:
  1. Avoid excessive soil moisture, especially late in the season, and provide good drainage.
  2. Do not bring infected tubers into storage if possible.
  3. When tubers are in storage, use high airflow and prevent water from condensing in the pile.
Chemical control: One application when plants are flowering has been shown effective in Colorado. A second application two weeks following the first application has an increased benefit. New in-furrow application at planting reduces cost over two aerial applications.

  1. Agri-Fos at 2 to 5 quarts/A in 10 gal water as a furrow spray applied in a band spray directly over top of row just before row is closed or 1.25 quarts/A in 90 to 375 gal water applied as a foliar spray on 5- to 14-day intervals 4-hr reentry.
  2. Quadris Ridomil Gold at 0.82 fl oz/1000 row feet applied in furrow using 3 to 15 gal/A of water or Ridomil Gold SL at 0.42 fl oz/1000 row feet in furrow at planting. See label for reentry intervals.
  3. Ranman at 0.42 fl oz/1000 row feet in furrow at planting or at 2.75 fl oz/A at hilling. In Idaho only (SLN ID-060011). Preharvest interval is 7 days. 12-hr reentry.
  4. Ridomil Gold Bravo SC at 2.5 pints/A following tuber initiation when the largest tubers are the size in diameter of a nickel. Make a second application 14 days later. Under severe pressure a third application may be made 14 days later. Do not use within 14 days of harvest. 48-hr reentry.
  5. Ridomil Gold SL at 0.42 oz/1000 row feet on a 6 to 8-inch band in a minimum of 3 gal of water/A at planting. Make application directly over the seed piece(s) prior to row closure or use markout application method (incorporated). 48-hr reentry.
  6. Ridomil Gold MZ at 2.5 lb/A. One application when tubers are nickel-size (flowering). A second application two weeks following the first where pink rot pressure is high. Do not use within 14 days of harvest. Note Contains an EBDC fungicide, so take care not to exceed seasonal limits. 48-hr reentry.
  7. Ridomil Gold Copper at 2 lb/A. One application when tubers are nickel-size (flowering). A second application two weeks following the first where pink rot pressure is high. Do not use within 14 days of harvest. Do not use with Polyram. 48-hr reentry.
Content edited by: Phil Hamm and Cynthia M. Ocamb on January 1, 2009
 
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