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Beginner

Scientific Name
Sclerotinia sclerotiorum

Identification

• Dark green water-soaked lesions develop on the vines or fruit
  
• The lesions enlarge rapidly, girdling the branches and stems, causing leaves to turn yellow and die
  
• White, cottony fungal growth may develop on infected fruit

Often Confused With
Phytophthora

Period of Activity
Temperatures ranging from 20– 25°C (68– 77°F) and continuous leaf wetness (high humidity and/or heavy dews) favour white mould development.

Scouting Notes
Inspect stems and developing fruit for small lesions.

Thresholds
None established. Fungicides applied during prolonged cool, wet conditions may help reduce the incidence of this disease.

Advanced

Scientific Name
Sclerotinia sclerotiorum

White mould has an extensive host range, infecting more than 300 plant species.  Beans are particularly susceptible to white mould infections. This is a minor disease in cucurbits, occasionally causing fruit rots during wet harvest seasons.

Identification
White mould symptoms normally first appear on dead tendrils or where an old leaf or spent flower rests on the fruit.  Vines damaged by sprayer tracks are also more prone to white mould infections. 

Dark green water-soaked lesions develop on the vines or fruit.  The lesions enlarge rapidly, girdling the branches and stems, causing leaves to turn yellow and die. White mould infections will cause the stem to split, revealing a dense white, cottony fungal growth.  Small, shrivelled, black (pea-like) sclerotia may be found embedded in the fungal growth.

White mould infections occasionally develop on fruit.  They tend to occur at the junction of the fruit and the stem or where an older leaf has been decomposing on the fruit surface.

Often Confused With
Phytophthora

Biology
White mould overwinters as sclerotia.  Moist soil conditions cause the sclerotia to germinate and produce a funnel-shaped apothecium. The apothecia release ascospores which then infect the crop. The ascospores are a weak pathogen and do not usually infect healthy plant tissue. They often invade through damaged leaves, spent flower blossoms or where the fruit sit on moist soil for an extended period of time.

Period of Activity
Temperatures ranging from 20– 25°C (68– 77°F) and continuous leaf wetness (high humidity and/or heavy dews) favour white mould development.

White mould sclerotia may live for several years in the soil.

Scouting Notes
Inspect stems and developing fruit for white mould lesions. 

Thresholds
Fungicides applied during cool, wet conditions may help reduce the incidence of this disease.

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.