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Ministry of Agriculture, Food and Rural Affairs

Pink Rot

Infection starting at the eye Advanced pink rot symptoms Pink rot symptoms after exposure to air Infected skin is easily rubbed off Pink rot symptoms Internal and external symptoms Discolouration of rotted areas after exposure to air Pink rot symptoms exposed to air Pink rot symptoms exposed to air Pink rot symptoms exposed to air
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Beginner

Scientific Name
Phytophthora erytroseptica

Identification
Pink rot is a tuber decay that occurs sporadically, usually near the end of the season. Infected areas of the tuber surface are purplish-black. The margin of the decay may be limited by a dark line. Infected skin is easily rubbed off.

Initially, the affected internal tissue is cream to light brown and has a rubbery consistency. When exposed to the air, the rot turns salmon-pink in about 20 minutes. This pink rot turns gray then black in 1 hour period.

Tuber decay can spread in storage when liquid oozes from rotting tubers creating favorable conditions for soft rot.
Occasionally, wilting of plants may occur as a result of pink rot infection.

Often Confused With
Late blight

Period of Activity
Infection of tubers usually occurs before or at harvest. Also pink rot may spread in storage.

Scouting Notes
Pink rot develops late in the season. Dig tubers at random after top killing to assess disease incidence prior to harvest. Pink rot is more likely to occur in low spots and areas of poor drainage.

Thresholds
Infected tubers should be graded out to avoid poor crop emergence in the spring and storage losses. Monitor storages closely to determine the development of hot spots.


Advanced

Scientific Name
Phytophthora erytroseptica

Identification
Pink rot is a tuber decay that occurs sporadically, usually near the end of the season. Infected areas of the tuber surface are purplish-black. The margin of the decay may be limited by a dark line. Infected skin is easily rubbed off.

Initially, the affected internal tissue is cream to light brown and has a rubbery consistency. When exposed to the air, the rot turns salmon-pink in about 20 minutes. This pink rot turns gray then black in 1 hour period.

Tuber decay can spread in storage when liquid oozes from rotting tubers creating favorable conditions for soft rot.
Occasionally, wilting of plants may occur as a result of pink rot infection.

Often Confused With
Late blight

Biology
This fungus attacks tubers, roots and stolons.

The fungus survives for many years in the soil. Tuber infection usually occurs before or at harvest. The disease is associated with excessive soil moisture, low spots in the field, over-irrigated areas and poorly drained soils.

The fungus penetrates the tubers mainly through stolons, but infection through lenticels and eyes can occur. Tubers may also be infected through wounds made during harvest and handling.

Pink rot may spread slowly in storage.

Russet Norkotah, Goldrush, Snowden and Kennebec are very susceptible to pink rot.

Period of Activity
Infection of tubers usually occurs before or at harvest. Also pink rot may spread in storage.

Scouting Notes
Pink rot develops late in the season. Dig tubers at random after top killing to assess disease incidence prior to harvest. Pink rot is more likely to occur in low spots and areas of poor drainage.

Thresholds
Infected tubers should be graded out to avoid poor crop emergence in the spring and storage losses. Monitor storages closely to determine the development of hot spots.

Management Notes

  • Applying an effective systemic fungicide when tubers are small reduces pink rot incidence.
  • If pink rot is detected in the field, do not harvest affected areas of fields.
  • A post-harvest treatment with a registered fungicide reduces pink rot spread in storage.
  • Avoid harvesting wet tubers whenever possible, maintain good air circulation and keep the storage temperature as low as possible. The pink rot pathogen is inactive below 4.4°C.