Skip to content.
Français

Some features of this website require Javascript to be enabled for best usibility. Please enable Javascript to run.

Ministry of Agriculture, Food and Rural Affairs

White Mold

White mold on pepper plant Sclerotia (white mold fungal structure) in stem White mold symptoms on pepper plant
Click to enlarge.

Beginner

Scientific Name 
Sclerotinia sclerotiorum

Identification

  • Lesions may occur anywhere on the stem
  • The stem becomes soft and bleached or light grey and large black fungal bodies (sclerotia) develop in or on the lesion
  • As a section of the stem dies, areas of the plant above the affected area also wilt and die
  • During cool, moist weather, a cottony growth appears on the affected areas
  • Infected fruit rots completely

Often Confused With
Phytophthora blight
Verticillium wilt

Period of Activity
Plant surfaces must remain continuously wet for 48-72 hours for infection to occur.  Disease develops most rapidly at 20- 25°C (68- 77°F), and not at all above 30°C (86°F).

Scouting Notes
Look for wilting plants or branches.  Light-coloured sections of stem are diagnostic of white mold.  The diagnosis can be confirmed if sclerotia (large black fungal bodies resembling rat droppings) are found in or on the affected area.

Thresholds
None established.

Advanced

Scientific Name 
Sclerotinia sclerotiorum

White mold has an extensive host range, infecting more than 300 plant species.  In peppers, this disease may be seen in very wet seasons, but is not usually a serious concern.

Identification
White mold symptoms normally first appear at a leaf scar or where a fallen flower sticks to the plant. 

Water-soaked lesions develop on the stem.  The lesions enlarge rapidly, girdling the branches and stems, causing leaves to turn yellow and die.  The stem lesions appear bleached or pale.  White, cottony fungal growth develops on affected stems.  Hard, black sclerotia (fungal structures) may be found in the fungal growth on or within the stem.  These sclerotia can persist in the soil for many years.  Parts of the plant above the infected area wilt and die.

Often Confused With
Phytophthora blight
Verticillium wilt

Biology
White mold overwinters as sclerotia.  Moist soil conditions cause the sclerotia to germinate and release spores which then infect the crop.  These Sclerotinia species are weak pathogens and do not usually infect healthy plant tissue.  They often invade through dead or injured tissue, or spent flower blossoms.

Period of Activity
Plant surfaces must remain continuously wet for 48- 72 hours for infection to occur.  Disease develops most rapidly at 20- 25°C (68- 77°F), and not at all above 30°C (86°F).

Scouting Notes
Look for wilting plants or branches.  Light-coloured sections of stem are diagnostic of white mold.  The diagnosis can be confirmed if sclerotia (large black fungal bodies resembling rat droppings) are found in or on the affected area.

Thresholds
None established.

Management Notes

  • Practice a 3– 4 year crop rotation away from susceptible crops (cucurbits, edible beans, soybeans, carrots and lettuce). 
  • The inclusion of a cereal crop in the rotation will significantly reduce the amount of sclerotia in the soil.
  • Dense canopies and poor air circulation that allow foliage to remain wet for extended periods encourage the development of white mold.
  • Sclerotinia species can also cause a collar rot of transplants.