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Sclerotinia trifoliorum J. Eriksson

Mycologia, ASCOMYCOTINA, HELOTIALES, SCLEROTINIACEAE .

Crops attacked: lucerne, .


[R]Common Names :

Rot,

Identification, Description, Biology, Epidemiology, Treatement, Possible misleading, Images


[R]Identification
Easily isolated on growth medium from sclerotia or mycelium.

[R]Description
The collar and the base of the stem -but not the root - form rot in late winter and early spring.
Lucerne dries in spring : some host plants suffer wilting of the top of the stem which crooks.
In clover, the above ground organs turn black at the same time in the season.
White mycelial growth on the affected organs clusters in masses to produce sclerotia.
Limits duration of the crop.

[R]Biology
The fungus persists as sclerotia on the soil.
Sclerotia germinate and generate 1-10 mm apothecia in autumn.
The ascospores cause spots to appear on the leaves which get larger and necrotic later in winter. In the cold season the disease spreads from plant to plant through mycelium progressing along the soil. The infected plants die in winter leaving debris containing sclerotia on the soil.

[R]Epidemiology
Ascospores are released at 10 -15 C. temperature.
The optimum for mycelial development is 15 -18 C.
Soil moisture and RH are necessary for the development of the disease.

[R]Treatement
Avoid sowing autumn crops in the high risk areas.
4-5 years rotations are recommended.
Chemical treatment should be carried out early in winter.

[R]Possible misleading
The sclerotia and apothecia of Sclerotinia sclerotiorum .

[R] Images

  1. Sclerotinia trifoliorum , White mould (VEGH I., INRA)
    White mould on alfalfa Sclerotia of Sclerotinia trifoliorum formation on alfalfa stems.

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