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How to Manage Pests

UC Pest Management Guidelines

Pink rot symptoms in freshly cut tuber (center), after half an hour (left), and after an hour (right).


Pink Rot

Pathogen: Phytophthora erythroseptica

(Reviewed 8/07, updated 8/07)

In this Guideline:


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.


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.


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, and avoid harvesting wet tubers. 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, treat 2 and 4 weeks before harvest.

Common name Amount/Acre R.E.I.+ P.H.I.+
(trade name)   (hours) (days)

Calculate impact of pesticide on air quality
Bee precaution pesticide ratings
When choosing a pesticide, consider information relating to the impact on environmental quality Not all registered pesticides are listed. Always read label of product being used.
  (Ridomil Gold MZ) 2.5 lb 48 14
  MODE OF ACTION GROUP NAME (NUMBER1): Phenylamide (4)/Multi-site contact (M3)
  COMMENTS: Make the first application at flowering and another 14 days later.
  (Ridomil Gold Bravo) 2 lb 48 14
  MODE OF ACTION GROUP NAME (NUMBER1): Phenylamide (4)/Multi-site contact (M5)
  COMMENTS: Make the first application at flowering and another 14 days later.
Restricted entry interval (R.E.I.) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (P.H.I.) 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 (for more information, see http://www.frac.info/). Fungicides with a different group number are suitable to alternate in a resistance management program. For fungicides with mode of action Group numbers 1, 4, 9, 11, or 17, make no more than one application 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.



[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Potato
UC ANR Publication 3463
R. M. Davis, Plant Pathology, UC Davis
J. Nuñez, UC Cooperative Extension, Kern Co.
B. J. Aegerter, UC Cooperative Extension, San Joaquin Co.
Acknowledgment for contributions to the disease section:
C. Smart, Plant Pathology, UC Davis

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