Soybeans: White Mould (Sclerotinia)

Excerpt from 2002 Edition of Agronomy Guide for Field Crops (Chapter 4)

Order 2009 edition of OMAFRA Publication 811: Agronomy Guide for Field Crops

Table of Contents

1. Incidence
2. Appearance
3. Management Strategies
4. Updates on Soybeans: White Mould (Sclerotinia)
5. Related links...

Incidence

White mould is a sporadic disease that occurs to some degree in Ontario. The disease is most damaging when cool, wet conditions occur during flowering or near harvest.

Appearance

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. Pods infected with white mould can result in seed infection. Infected seed has a loose, white, fungal growth on the seed. Do not use seed from infected fields.

Plate 70. White mould (Sclerotinia) produces a white, cotton-like fungal growth on diseased stems.

Plate 71. Stems infected with white mould die, a small black bodies (Sclerotia) can be seen on the stem.

Management Strategies

In fields with a history of white mould, avoid growing other host crops such as canola, edible beans, buckwheat and sunflowers for 3-4 years. Planting no-till wheat after soybeans will cause the new sclerotia to remain on the soil surface. Only those sclerotia found in the top 2.5 cm of the soil will germinate. If no tillage is carried through the following crops, most of the sclerotia left on the surface will have been expended. Deeply buried sclerotia are unlikely to cause a problem for future bean crops, unless they are brought to the surface through tillage.

Some differences in susceptibility to this disease have been noted between varieties. No resistant varieties have been identified, but field observations indicate that early varieties in a geographic area are less prone to an epidemic than later varieties. Similarly, varieties with greater lodging resistance tend to be more resistant to white mould. For soybean fields with a history of severe white mould infection, producers should consider planting varieties that require 200-300 fewer crop heat units than available for the area and that possess superior resistance to lodging.

Updates on Soybeans: White Mould (Sclerotinia)

• Field Crop Protection Guide - Publication 812
  • Soybeans: White Mould

Related links...

• Diseases
• Soybeans