White mould (Sclerotinia sclerotiorum)

White mould: biology

White mould, also known as Sclerotinia stem rot, is caused by the fungus Sclerotinia sclerotiorum. The disease is an annual threat to soybean production – especially when conditions are cool, cloudy, wet and humid during flowering. White mould persists in soybean fields due to structures called sclerotia, which can survive in the soil for up to seven years.

White mould is most problematic in soybean fields with high plant populations, narrow row spacing, and an early-closing canopy. Depending on severity, white mould can lead to reduced yields, standability and seed quality.

White mould: damage description

Cotton-like growth on soybeans

Sclerotia in stems

White mould in soybean crop

Stems and pods infected with white mould are pale brown and water-soaked in appearance. Frequently, a white, cotton-like growth and small black bodies (sclerotia) can be seen on or within stems of diseased plants. Plants are generally killed in patches late in the growing season. The black bodies of white mould are sometimes found in the seed at harvest. Pods infected with white mould can result in seed infection.

White mould: management

Implementing a few minor changes on the farm can help improve the way growers manage this potentially devastating disease. Practice these tips for white mould management:

Keep good field records of disease level
Select varieties with the best available level of tolerance, appropriate maturity and a plant type that is upright, non-bushy with good lodging tolerance
Avoid dense canopies – reduce plant populations and increase row width
Rotate with non-host crops (e.g. corn and wheat)
In fields with a history of white mould, avoid growing other host crops such as canola, dry edible beans, buckwheat and sunflowers for three to four years
Reduce tillage but avoid soybeans on soybeans
Apply fungicides in high-risk fields at proper timing and coverage

Check out our infographic to learn how to get more from your fungicide application targeting white mould.

Sources:
http://www.omafra.gov.on.ca/english/crops/pub811/pub811.pdf
https://crops.extension.iastate.edu/cropnews/2014/07/managing-white-mold-soybean
http://www.omafra.gov.on.ca/english/crops/field/news/croptalk/2015/ct-0315a3.htm

Resources

Managing white mould

Agronomic Sales Representative Marijke Van Andel explains how genetics, canopy management and fungicides can help growers manage white mould in their soybeans.

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Manage white mould in soybeans with a holistic approach

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