Soybeans: Brown Stem Rot, Stem Canker and Sudden Death Syndrome

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
   • Symptom Expression on Roots, Stems and Leaves for Brown Stem Rot, Stem Canker and Sudden Death Syndrome on Soybeans - Table 4-23
   • Brown Stem Rot (BSR)
   • Stem Canker
   • Sudden Death Syndrome (SDS)
3. Disease Cycle
4. Management Strategies
5. Updates on Soybeans: Brown Stem Rot, Stem Canker and Sudden Death Syndrome
6. Related links...

Incidence

All three diseases are found in all soybean-growing areas of Ontario but are more common in southwestern counties. All of these diseases are increasing, most likely as a result of changes in tillage practices. Yield losses range from a few bushels to significant portions of the field being killed (especially for sudden death syndrome).

Appearance

To aid in correctly identifying these diseases, refer to Table 4-23, Symptom Expression on Roots, Stems and Leaves for Brown Stem Rot, Stem Canker and Sudden Death Syndrome on Soybeans.

Brown Stem Rot (BSR)

Symptoms of the disease generally develop in August during pod fill. Upper leaves develop yellow and necrotic areas between the veins similar to sudden death syndrome. Plants wilt suddenly, and pods are poorly filled. The disease is more prevalent with minimum tillage.

Stem Canker

This disease may cause seedling damping off and wilt but commonly affects soybean plants after flowering. Plants wilt suddenly, and leaves and petioles droop, resembling symptoms of Phytophthora root rot. Brownish-red lesions appear on the exterior of diseased plants at lower nodes. The pith of diseased plants is generally brown near the nodes. The fungus can also cause a stem or tip dieback late in the growing season. The fungus can cause seed mould similar to Phomopsis seed mould. Stem canker overwinters in crop debris and is more prevalent in minimum tillage situations.

Plate 75. Stem canker causes plants to wilt suddenly with brownish-red lesions near lower nodes.

Sudden Death Syndrome (SDS)

Infected plants wilt and die very quickly in July and August. Interveinal chlorosis and necrosis of the upper leaves and defoliation may occur. Petioles are generally retained. Wet soils and warm temperatures are conducive to disease development. A slight brownish discolouration occurs in crowns of affected plants. The disease is frequently but not always associated with soybean cyst nematode.

Plate 74. Plants infected with sudden death syndrome wilt and die quickly. Interveinal chlorosis and necrosis of upper leaves may occur.

Disease Cycle

All of these fungi survive long periods in crop debris (residue) in the soil. Brown stem rot infects early in the growing season but does not appear until a month before harvest. Conditions during pod fill affect disease development. Development is favoured when conditions during pod-fill are cool and wet followed by hot and dry. Stem canker prefers moderately warm, wet weather and occurs from mid-July to maturity. Plants infected with sudden death syndrome begin showing symptoms from flowering to maturity and prefer cool, moist soil conditions. Well-fertilized or vigorously growing fields are most likely to show the sudden death syndrome symptoms.

Management Strategies

Crop rotation with corn and small grains will reduce the incidence of disease. These diseases occur most often on reduced tillage fields. Incorporation or removal of infested residue will reduce the risk of these diseases. A few resistant or tolerant varieties are available. Check with your seed company for variety profiles.

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Updates on Soybeans: Brown Stem Rot, Stem Canker and Sudden Death Syndrome

No updates available at this time.

Related links...

• Diseases
• Soybeans
• Field Crop Protection Guide - Publication 812