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Tomato Diseases | Sclerotinia White Mold

Sclerotinia White Mold


  • Fluffy, cottony white mold develops on the stems, leaves, petioles, and flowers.
  • Clumps of mycelium form small hard black structures, known as sclerotia, with whitish-pink insides when cut open. Sclerotia range in shape from round to oblong, often about the size of large rice grains.  Sclerotia can be very irregular in shape and size, depending on where (inside or outside the plant) they are formed.
  • Bleached areas and watery soft rots form on the stems, later drying and becoming brittle.
  • Stems can be girdled and the plant wilts and dies.

sclerotinia copy 2 WhiteMoldPepper1 copy White mold pepper copy
Sclerotinia white mold symptoms on tomato (left) and pepper (center; right).

Favorable Environmental Conditions

  • Cool temperatures from 59 to 70°F
  • 16 to 72 hours of continuous wetness
  • Relative humidity > 90%

Often Confused With

Scouting Notes

  • Scout seedlings and during times of flowering, where the plants are most susceptible. Intensify scouting during spring and fall or whenever temperatures are cool and humidity high.
  • Look for any white cottony growth on stems, leaves, and other plant parts.
  • Remove and destroy any infected plants in order to prevent further infection.  Remove soil around the base of the stem that may contain sclerotia produced on the plant.