Sclerotinia Stem Rot (White Mold)

Symptoms:

Initial lesions usually develop at stem nodes during or after flowering.

The lesions expand and the tops of the plants initially become grayish-green and then wilt and die.

Infected areas often become soft and watery, and become covered with white moldy growth in moist conditions.

Hard, black sclerotia develop on or inside infected stems and pods.

Occurrence of white mold varies widely from year to year and from location to location.

Pathogen Involved:

Sclerotinia sclerotiorum (a fungus).

Survives from year-to-year in soil or stems in the form of hard black masses of mycelium (sclerotia).

Sclerotia germinate near the soil surface to form small mushroom-shaped structures called apothecia, which produce ascospores that are spread by wind to infect dead soybean flowers.

Seed lots can be contaminated with sclerotia and seeds can be infected with the pathogen.

The host range of this pathogen includes many broadleaf plants, but not corn or small grains.

Time of Occurrence:

After flowering.

Conditions Favoring Disease:

Cool moist weather is required for this diseases to occur.	Narrow rows.	High fertility.
Lack of air circulation under soybean canopy.	Early planting.	High plant populations.

Disease Management:

Use seed free of Sclerotinia contamination and infection.	Reduce or avoid irrigation until seed has set.
Careful selection of soybean varieties may be helpful because some varieties are more susceptible than others.
Foliar fungicides may be beneficial but may not be economically beneficial.

For more information on white mold, go to http://whitemold.uiuc.edu.

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