Agriculture: Potato Pest Management Guidelines

Pink Rot

  • Phytophthora erythroseptica
  • Symptoms and Signs

    Pink rot appears as a decay of tubers that usually begins at or near the stem end of potatoes in the field or through eyes of potatoes in storage. Infected tissue becomes somewhat rubbery but not discolored. When an infected tuber is cut, the rotted portion is delineated by a dark line at its margin. With exposure to air, the surface of the decay turns a salmon pink color, which later turns to brown and then finally black. Roots and lower stems may also rot, causing a wilt and early dying of plants. The spread of pink rot may continue in storage.

    Comments on the Disease

    Pink rot is a major problem of potatoes. The pathogen survives for long periods in the soil and becomes active when the soil is saturated with water.

    Management

    Pink rot is most frequently seen in mature plants approaching harvest. It is much worse when saturated soil is accompanied by warm temperatures. Avoid prolonged saturation of soils during irrigation, provide good drainage, minimize wounding, and avoid harvesting wet tubers or tubers with pulp temperatures above 65°F. Maintain good airflow, avoid the accumulation of moisture on tubers, and maintain low temperatures during storage because the fungus is inactive below 40°F. In areas where pink rot is a problem, apply fungicide 2 and 4 weeks before harvest.

    Common name Amount per acre REI‡ PHI‡
    (Example trade name) (hours) (days)
    Not all registered pesticides are listed. The following are ranked with the pesticides having the greatest IPM value listed first—the most effective and least likely to cause resistance are at the top of the table. When choosing a pesticide, consider information relating to the pesticide's properties and application timing, honey bees, and environmental impact. Always read the label of the product being used.
     
    A. MEFENOXAM/MANCOZEB
      (Ridomil Gold MZ) 2.5 lb 48 14
      MODE OF ACTION GROUP NAME (NUMBER1): Phenylamide (4)/ Dithiocarbamates and relatives (M3)
      COMMENTS: Make the first application at flowering and another 14 days later.
     
    B. MEFENOXAM/CHLOROTHALONIL
      (Ridomil Gold Bravo SC) 2.5 pts 48 14
      MODE OF ACTION GROUP NAME (NUMBER1): Phenylamide (4)/ Chloronitriles (phthalonitriles) (M5)
      COMMENTS: Make the first application at flowering and another 14 days later.
     
    POSTHARVEST - STORED POTATO TUBERS
    A. PHOSPHITES
    (Phostrol) 0.1 gallon/ton of tubers/0.5 gal 4 NA
    MODE-OF-ACTION GROUP NAME (NUMBER1): Phosphonates (33)
    Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (PHI) is the number of days from treatment to harvest. In some cases the REI exceeds the PHI. The longer of two intervals is the minimum time that must elapse before harvest.
    1 Group numbers are assigned by the Fungicide Resistance Action Committee (FRAC) according to different modes of actions. Fungicides with a different group number are suitable to alternate in a resistance management program. In California, make no more than one application of fungicides with mode of action group numbers 1, 4, 9, 11, or 17 before rotating to a fungicide with a different mode of action group number; for fungicides with other group numbers, make no more than two consecutive applications before rotating to fungicide with a different mode of action group number.
    NA Not applicable
    Text Updated: 03/19
    Treatment Table Updated: 03/19